CN108882985B - Thin wall support - Google Patents

Thin wall support Download PDF

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Publication number
CN108882985B
CN108882985B CN201680082165.5A CN201680082165A CN108882985B CN 108882985 B CN108882985 B CN 108882985B CN 201680082165 A CN201680082165 A CN 201680082165A CN 108882985 B CN108882985 B CN 108882985B
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ring
stent
link
marker
crown
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CN108882985A (en
Inventor
迪姆·达
查德·阿布纳赛尔
森蒂尔·埃斯瓦瑞
林志成
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Abbott Cardiovascular Systems Inc
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Abbott Cardiovascular Systems Inc
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Priority claimed from US14/973,632 external-priority patent/US10143573B2/en
Priority claimed from US14/973,628 external-priority patent/US9956099B2/en
Priority claimed from US14/973,633 external-priority patent/US9861507B2/en
Application filed by Abbott Cardiovascular Systems Inc filed Critical Abbott Cardiovascular Systems Inc
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
    • A61F2/915Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/95Instruments specially adapted for placement or removal of stents or stent-grafts
    • A61F2/958Inflatable balloons for placing stents or stent-grafts
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
    • A61F2/915Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other
    • A61F2002/91516Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other the meander having a change in frequency along the band
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • A61F2/91Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
    • A61F2/915Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes with bands having a meander structure, adjacent bands being connected to each other
    • A61F2002/9155Adjacent bands being connected to each other
    • A61F2002/91575Adjacent bands being connected to each other connected peak to trough
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0004Rounded shapes, e.g. with rounded corners
    • A61F2230/0006Rounded shapes, e.g. with rounded corners circular
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0028Shapes in the form of latin or greek characters
    • A61F2230/0054V-shaped
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0028Shapes in the form of latin or greek characters
    • A61F2230/0056W-shaped, e.g. M-shaped, sigma-shaped
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2250/00Special features of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2250/0058Additional features; Implant or prostheses properties not otherwise provided for
    • A61F2250/0096Markers and sensors for detecting a position or changes of a position of an implant, e.g. RF sensors, ultrasound markers
    • A61F2250/0098Markers and sensors for detecting a position or changes of a position of an implant, e.g. RF sensors, ultrasound markers radio-opaque, e.g. radio-opaque markers

Abstract

The thin-walled stent includes a radiopaque marker attached to the linkage rod. In a first example, the marker is held by the head at one or both ends on the strut by swaging. In a second example of the thin-walled stent, the links are modified to avoid interference during crimping. In a third example, the distal end of the thin-walled stent is modified to improve the delivery capabilities of the thin-walled stent. These features are combined in a fourth example.

Description

Thin wall support
Technical Field
The present invention relates to bioabsorbable stents; more particularly, the present invention relates to bioabsorbable stents for treating anatomical lumens of the body.
Background
Radially expandable endoprostheses are artificial devices adapted to be implanted in anatomical lumens. "anatomical lumen" refers to the lumen or tubular body of a tubular organ (e.g., blood vessels, urinary tract, and bile duct). Stents are an example of an endoprosthesis, which is generally cylindrical in shape and is used to hold open and sometimes deploy a portion of an anatomical lumen. Stents are often used to treat atherosclerotic stenosis in blood vessels. "stenosis" refers to a reduction or narrowing of the diameter of a body passageway or orifice. In these treatments, the stent strengthens the vessel wall and prevents restenosis following angioplasty in the vascular system. "restenosis" refers to the reoccurrence of stenosis after a blood vessel or heart valve has been significantly successfully treated (e.g., by balloon angioplasty, stent implantation, or valvuloplasty).
Treatment of a diseased or diseased site with a stent involves the delivery and deployment of the stent. "delivery" refers to the introduction and delivery of a stent to a desired treatment site, such as a lesion, via an anatomical lumen. "deployment" corresponds to the expansion of the stent within the lumen of the treatment area. Delivery and deployment of a stent is accomplished by positioning the stent around an end of a catheter, inserting the end of the catheter percutaneously into an anatomical lumen, pushing the catheter within the anatomical lumen to a desired treatment location, expanding the stent at the treatment location, and removing the catheter from the lumen.
Stents and stents have traditionally been divided into two general types-balloon expandable and self-expanding. The latter type expands (at least partially) within the vessel to a deployed or expanded state when the radial constraint is removed, while the former relies on an externally applied force to shape it from a crimped or stored state to a deployed or expanded state.
Self-expanding stents are designed to expand significantly when the radial constraint is removed, such that a balloon is generally not required to deploy the stent. Self-expanding stents do not undergo or undergo a plastic or inelastic deformation equivalent to zero when stored in a sheath or expanded in a lumen (with or without an auxiliary balloon). Balloon expandable stents or stents, when crimped and subsequently deployed by a balloon, instead undergo significant plastic or inelastic deformation.
In the case of a balloon-expandable stent, the stent is attached around the balloon portion of a balloon catheter. The stent is compressed or crimped over the balloon. Crimping is accomplished by using an iris type or other form of crimper such as the crimper disclosed and shown in US 2012/0042501. A large amount of plastic or inelastic deformation occurs when a balloon-expandable stent or scaffold is crimped and subsequently deployed by a balloon. At the treatment site within the lumen, the stent is expanded by inflating the balloon.
Internal stents must be able to meet a number of basic, functional requirements. The stent (or stent) must be able to withstand radial compressive forces as it supports the vessel wall. Therefore, the inner stent must have sufficient radial strength. After deployment, the inner stent must adequately retain its size and shape over its useful life, although the inner stent may be subjected to various forces. In particular, despite these forces, the stent must adequately maintain the vessel at a prescribed diameter for the intended treatment time. The treatment time may correspond to the time required to reconstruct the vessel wall, after which the stent is no longer needed.
Examples of bioabsorbable polymeric stents include those described in U.S. patent No.8,002,817 to Limon, U.S. patent No.8,303,644 to Lord, and U.S. patent No.8,388,673 to Yang. Fig. 1 shows a distal region of a bioabsorbable polymeric stent designed for delivery through an anatomical lumen using a catheter and plastic expansion using a balloon. The stent is cylindrical in shape with a central axis 2 and comprises a pattern of interconnected structural elements which will be referred to as ribbon arms or struts 4. The axis 2 extends through the centre of the cylindrical shape formed by the struts 4. The compressive forces involved in the compression and expansion process are typically distributed throughout the strut 4, but concentrated at the flex elements, crowns or strut junctions. The struts 4 comprise a series of annular struts 6 connected to one another at crowns 8. The annular struts 6 and the crowns 8 form sinusoidal rings 5. The ring 5 is arranged longitudinally and centered on the axis 2. The stay 4 further comprises a link stay 9 connecting the rings 5 to each other. The ring 5 and the link struts 9 together form a tubular stent 10, the tubular stent 10 having an axis 2 representing the bore or longitudinal axis of the stent 10. The loop 5d is located at the distal end of the stent. The crowns 8 form smaller angles when the stent 10 is crimped on a balloon, and the crowns 8 form larger angles when the stent 10 is plastically expanded by a balloon. After deployment, the stent may be subjected to static and cyclic compressive loads from the surrounding tissue. The ring 5 is configured to maintain the stent in a radially expanded state after deployment.
The stent may be made of biodegradable, bioabsorbable, bioresorbable, or bioerodable polymers. The terms biodegradable, bioabsorbable, bioresorbable, biosoluble, or bioerodable refer to the property of a material or stent to degrade, absorb, resorb, or erode away from an implanted region. Stents may also be constructed from bioerodible metals and alloys. In contrast to durable metal stents, the stent is intended to remain in the body for only a limited period of time. In many therapeutic applications, it is necessary that the stent be present in the body for a limited period of time until it performs its intended function (e.g., maintaining vessel patency and/or drug delivery). In addition, biodegradable stents have been shown to improve healing of anatomical lumens compared to metallic stents, which may lead to a reduced incidence of late stage thrombosis. In these cases, it is desirable to treat the blood vessel with a polymeric stent, particularly a bioabsorbable or bioresorbable polymeric stent, as opposed to a metallic stent, so that the presence of the prosthesis in the blood vessel is temporary.
Polymeric materials contemplated for use as a polymeric stent may be described by comparison to metallic materials used to form an inner stent, such as poly (L-lactide) ("PLLA"), poly (D, L-lactide-co-glycolide) ("PLGA"), poly (D-glycolide-co-lactide), or poly (L-lactide-D-lactide co-polymer) ("PLLA-PDLA copolymer") having less than 10% D-lactide, poly (L-lactide-co-caprolactone), poly (caprolactone), PLLD/PDLA stereocomplex, and mixtures of the foregoing polymers, in the following manner. Polymeric materials generally have a lower strength to volume ratio than metals, which means that more material is required to provide equivalent mechanical properties. Therefore, the struts must be made thicker and wider in order for the stent to have the required strength to support the lumen wall at the desired radius. Stents made from these polymers tend to be brittle or have limited fracture toughness. The inherent anisotropy in materials and the rate-dependent inelastic properties (i.e., the strength/stiffness of the material is dependent on the rate of deformation of the material in addition to changes in temperature, hydration, heat history) add complexity only when used with polymers, particularly bioabsorbable polymers such as PLLA or PLGA.
An additional challenge with using bioresorbable polymers (and polymers that typically contain carbon, hydrogen, oxygen, and nitrogen) for the scaffold structure is that the material is radiolucent without radiopacity. Bioabsorbable polymers tend to be X-ray absorbing, similar to body tissue. A known way to address this problem is to attach radiopaque markers to structural elements of the stent, such as struts, bar arms, or links. For example, fig. 1 shows a link element 9d connecting a distal ring 5d with an adjacent ring 5. The link member 9d has a pair of holes. Each hole holds a radiopaque marker 11. The use of markers 11 on stents 10 presents challenges. A reliable means of attaching the marker 11 to the linkage element 9d is required so that the marker 11 does not detach from the stent during processing steps such as crimping the stent onto the balloon or when the stent is expanded from a crimped state by the balloon. Both of these conditions-crimping and balloon expansion-are particularly problematic for attaching markers to stents because both of these conditions cause significant plastic deformation within the stent body. If such deformation causes significant out-of-plane or irregular deformation of the struts supporting or proximate to the marker, the marker may be dislodged (e.g., the marker may fall out of its hole if the struts holding the marker are twisted or bent during crimping). Stents with radiopaque markers and methods for attaching markers to stent bodies are discussed in US 20070156230.
For thin-walled stents, there is a need to improve the reliability of the securement of radiopaque markers to the stent. Associated with this need, there is a need to improve the performance characteristics of stents, particularly thin-walled stents made of bioabsorbable materials that must travel around curved anatomical structures.
Disclosure of Invention
Disclosed are bioabsorbable stents having radiopaque markers and stent structures supporting such radiopaque materials and which can reduce the profile of crimping and/or improve conformance to a catheter when the catheter to which the stent is mounted is pushed through a curved anatomy.
The stents disclosed herein are suitable for meeting one or a combination of the following objectives:
(i.) the crimping profile of a thin-walled stent carrying radiopaque markers is reduced,
(ii.) affixing the marker to the thin-walled stent,
(iii.) when the thin-walled stent is deformed during crimping, expanded by a balloon at the target vessel site or delivered to the target site, the strain energy accumulated within the marker-retaining structure is reduced, and
(iv) for a thin-walled stent or a stent comprising PLLA and having a wall thickness greater than 125 microns, the end ring flare is reduced at the distal end of the stent.
Since the stent is thin-walled, the need to improve certain critical regions of the stent, which were not previously problematic when the stent was used with higher wall thicknesses, has been met through testing. An example of a stent with a wall thickness above 158 microns is described in US 2010/0004735. It has been found that when the wall thickness is significantly reduced, there is a need to improve the arrangement, shape and size of the ring and link elements, particularly at the distal end of the stent, as compared to pre-existing bioabsorbable stents (e.g., from 160 micron wall thickness to 100 micron wall thickness).
A thin-walled stent is sought because of the clinical need to maintain a low profile for a strut that is exposed to blood. Hemocompatibility (also known as hemocompatibility or thrombus resistance) is a desirable property for stents and stents. Adverse events of stent thrombosis, although low frequency events, can contribute to high morbidity and mortality. To mitigate the risk of thrombosis, dual antiplatelet therapy is performed with all coronary stents and stent implantations. This is to reduce thrombosis due to surgery, vascular injury and the implant itself. Stents and stents are exosomes and both have some degree of procoagulability. The procoagulability of a stent refers to its propensity to form thrombus and is due to several factors including strut thickness, strut width, strut shape, total stent surface area, stent pattern, stent length, stent diameter, surface roughness and surface chemistry. Some of these factors are interrelated. A low strut profile also causes less neointimal hyperplasia, as the neointima will grow to the extent necessary to cover the struts. As such covering is a necessary step to complete healing. Thinner struts are believed to endothelialize and heal more quickly.
According to various aspects of the present invention, there is provided a thin-walled stent ("stent"), a medical device, a method of making such a stent, a method of making a marker and attaching the marker to a strut, link or strip arm of a stent, a method of crimping, or a method of assembly of a medical device comprising such a stent having one or more or any combination of the following (1) to (15):
(1) crimping the scaffold to a theoretical minimum crimped diameter (D-min);
(2) the stent wall thickness is less than 125 microns, less than 100 microns, about 100 microns, or about 93 microns;
(3) the wavelength of the ring connected to the marker link is greater than the wavelength of the other rings not connected to the marker link, and/or the wavelength of the ring connected to the marker length has a different length;
(4) the distance from the W crown part to the adjacent U crown part is larger than the distance from the Y crown part to the adjacent U crown part;
(5) the stent is made of a catheter comprising poly (L-lactide);
(6) crimping the scaffold to the balloon, wherein the scaffold comprises a crimped state as shown and described in connection with fig. 4D, 6A, or 7A;
(7) a method of crimping any of the stents described in conjunction with fig. 3, 4, 5, 6, or 7;
(8) a method of attaching a radiopaque marker to a stent;
(9) a marker link having the dimensions shown and described in connection with FIG. 2C;
(10) the ring has n peaks, where n is greater than 5, or greater than 6 and less than or equal to 12;
(11) the ring has 2 wavelengths of a first size and n-2 wavelengths of a second size, the first size being larger than the second size;
(12) the ring connected to the marker link at the W crown has a first width and the adjacent ring connected to the marker link has a second width that is greater than the first width;
(13) the ring connected to the marker link at the W crown has a wider flat portion or is wider than the flat portion connected to the marker link at the Y crown and adjoining the first ring;
(14) a first distance between rings adjoined by a marker link is greater than a second distance between rings not adjoined by a marker link; and
(15) a first distance between rings adjoined by the nonlinear link marker link is greater than a second distance between rings not adjoined by the nonlinear link marker link.
(16) D-min is about 1mm or less than 1mm
(17) The Aspect Ratio (AR) of a marker link for a thin-walled stent is between about 4 and 5 or about 4.5, where AR is defined as the maximum width of the marker link divided by the wall thickness at the marker link.
(18) The first wavelength or 1/2 wavelength of the first ring is greater than the second wavelength or 1/2 wavelength of the adjoining second ring.
(19) A first wavelength or 1/2 wavelength between two peaks of a ring is different from a second wavelength between two other peaks of the same ring.
(20) The rings are sinusoidal or saw-toothed.
(21) A half wavelength measured from a W crown formed between the marker link and the first ring is about 15% higher than a half wavelength measured from a Y crown formed between the marker link and a second ring adjacent to the first ring; for a marker link, the marker link has a maximum width that is about 200% higher than the maximum width of a non-marker link.
(22) A wavelength measured from a W crown formed between the marker link and the first ring is between about 5% and 10% higher than a wavelength measured from a Y crown formed between the marker link and a second ring adjacent to the first ring; for a marker link, the marker link has a maximum width that is about 200% higher than the maximum width of a non-marker link.
(23) The wavelength measured from the W crown/peak formed between the marker link and the ring is between about 5% and 10% higher than the wavelength measured from between the other peaks of the ring; for a marker link, the marker link is about 200% higher than the maximum width of the non-marker link.
(24) The crown has a B1 greater than a crown width B2; for example, the crown width B1 is approximately 350% -400% greater than the crown width B2.
(25) The ring spacing a12 between the first and second rings is greater than the ring spacing a23 between the second and third rings; for example, A12 is about 40% larger than A23.
(26) The connecting rod is a straight connecting rod or a nonlinear connecting rod; such as link 20 and link 636.
(27) For the marker link, length c1 is approximately 36% higher than length c 2.
(28) For a non-linear link, length c1 is approximately 36% higher than length c 2.
(29) A medical device, comprising: a thin-walled stent having a web of rings interconnected by links, wherein one ring has a plurality of peaks, wherein a peak is one of a U-crown, a Y-crown, and a W-crown, each ring extending circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); and a marker link extending between the first and second rings of the ring, the marker link comprising a structure having an aperture and a radiopaque material received in the aperture; wherein the marker link forms a first ring W crown with the first ring and a second ring Y crown with the second ring, wherein a 1/2 wavelength of the first ring measured from the first ring W crown to an adjacent U crown of the first ring is greater than a 1/2 wavelength of the second ring measured from the second ring Y crown to an adjacent U crown of the second ring.
(30) The medical device of (29) in combination with one or more of (a) to (g), or any combination thereof:
(a) wherein the length of the marker link is greater than the length of a link connecting the second ring with a third ring adjacent to the second ring;
(b) wherein the marker link comprises a first link portion extending from the construct to the first ring W crown and a second link portion extending from the second ring Y crown to the construct, wherein the width of the first link portion is greater than the width of the second link portion;
(c) wherein the length of the first length portion is less than the length of the second link portion;
(d) wherein the structure comprises a first hole and a second hole, each hole containing a radiopaque material, wherein the first hole and the second hole are aligned parallel to the axis a-a;
(e) wherein the first ring comprises a first peak, a second peak, and a third peak, the first peak corresponding to the first ring wchirth, the second peak adjacent to the first peak and the third peak adjacent to the second peak, wherein a second wavelength extending from the second peak to the third peak is less than a first wavelength extending from the first peak to the second peak;
(f) wherein the flat portion of the crown of the first ring W is larger than the flat portion of the crown of the third ring W of the third ring adjacent to the second ring and/or the flat portion of the crown of the fourth ring W of the first ring; and
(g) wherein the wavelength of a first ring forming the crowns of the first ring W is longer than the wavelength of a second ring forming the crowns of the second ring Y.
(31) A medical device, comprising: a thin-walled stent having a proximal portion and a distal portion formed from a web of rings interconnected by links, wherein each ring has a plurality of peaks, wherein a peak is one of a U-crown, a Y-crown, and a W-crown, and each ring extends circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); a marker link extending between the first and second rings of the ring, the marker link including a structure having an aperture and a radiopaque material received in the aperture; wherein the marker link forms a first ring W crown with the first ring and a second ring Y crown with the second ring, the first ring W crown corresponding to the first peak; and wherein a first wavelength of the first ring measured from the first peak to a second peak of the first ring adjacent to the first peak is greater than a second wavelength of the first ring measured from the second peak to an adjacent third peak of the first ring.
(32) The medical device of (31) in combination with one or more or any combination of (a) to (c):
(a) wherein the first ring has n peaks and n wavelengths, wherein n is at least 6 and no more than 12, and wherein the first and second wavelengths measured from above and below the first peak and the first peak, respectively, are greater than the remaining n-2 wavelengths measured from between the n-1 peaks;
(b) wherein all remaining n-2 wavelengths have the same length;
(c) wherein the length of the marker link is approximately equal to the length of the link connecting the second ring with the third ring.
(33) A medical device, comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; a thin-walled stent crimped to the balloon, the stent having a proximal portion and a distal portion formed from a web of rings interconnected by links, wherein each ring has a plurality of peaks, wherein a peak is one of a U-crown, a Y-crown, and a W-crown, and each ring extends circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); a marker link extending between the first and second rings of the ring, the marker link including a structure having an aperture and a radiopaque material received in the aperture; wherein the marker link forms a first ring Wcrown with the first ring and a second ring Ycrown with the second ring, the first ring Wcrown corresponding to the first peak; wherein a first wavelength of the first ring measured from the first peak to a second peak adjacent to the first peak is greater than a second wavelength of the first ring measured from the second peak to a third peak adjacent to the second peak; wherein the thin-walled stent has an outer diameter of about D-min; and wherein D-min ═ 1/pi × [ (n × strut _ width) + (m × link _ width) ] +2 × t.
(34) The medical device of (33) in combination with one or more or any combination of (a) to (d):
(a) wherein a maximum width of the structure, measured along axis B-B, is greater than a maximum width of a link extending between the second ring and a third ring adjacent the second ring;
(b) wherein the marker link includes a first link portion extending from the construct to the W crown and a second link construct extending from the Y crown to the construct, wherein the first link portion has a width greater than a width of the second link portion;
(c) wherein the length of the first length portion is less than the length of the second shaft portion; and
(d) wherein the structure includes a first aperture and a second aperture containing a radiopaque material, wherein the first aperture and the second aperture are aligned parallel to the axis a-a.
(35) A method of manufacturing a medical device, comprising: using a tube comprising poly (L-lactide); forming a thin-walled stent pattern from a tube, the stent having a proximal portion and a distal portion formed from a web of rings interconnected by links, wherein each ring has a plurality of peaks, wherein a peak is one of a U-crown, a Y-crown, and a W-crown, and each ring extends circumferentially in an undulating form along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); the thin-walled stent includes at least one marker link extending between a first ring and an adjoining second ring of rings, the marker link including a structure having an aperture; placing a radiopaque material in the marker hole, wherein the hole has a first dimension prior to placement of the material and a second dimension greater than the first dimension after placement of the material, and wherein the structure has a width measured along axis B-B; and crimping the thin-walled stent to a balloon catheter; wherein the thin-walled stent is crimped to about a theoretical minimum crimp diameter (D-min); and wherein the crowns adjacent to and above and below the structure do not overlap the structure.
(36) The medical device of (35) in combination with one or more or any combination of (a) to (c):
(a) wherein the marker link forms a first ring W crown with the first ring and a second ring Y crown with the second ring, the first ring W crown corresponding to the first peak, and wherein a first wavelength of the first ring measured from the first peak to a second peak adjacent to the first peak is greater than a second wavelength of the first ring measured from the second peak to an adjacent third peak;
(b) wherein the marker link forms a first loop W crown with the first loop and a second loop Y crown with the second loop, the first and second U crowns adjacent to and above and below, respectively, the first strut extending from the first loop W crown to the first U crown and the second strut extending from the first loop W crown to the second U crown, wherein a distance between the first and second U crowns or a distance between the second strut to the first strut is greater than or equal to a maximum width of the marker structure measured along axis B-B; and
(c) wherein the width of the marker structure is greater than the maximum width of the tie rod connecting the second ring with the adjacent third ring.
(37) A medical device, comprising: a thin-walled stent having a proximal portion and a distal portion formed by a web of rings interconnected by links of the thin-walled stent, wherein each ring has a plurality of crowns, including a U crown and at least one of a Y crown and a W crown, each ring extending circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); the proximal portion comprises an outermost proximal ring adjoining the first proximal ring by a first proximal link, and the first proximal ring adjoins the second proximal ring by a second proximal link; the distal portion including an outermost distal ring adjoined to the first distal ring by a first distal link, and the first distal ring adjoined to the second distal ring by a second distal link; wherein-the first proximal link comprises a proximal marker link comprising a proximal aperture containing a radiopaque material, and-the first distal link is free of a link holding a radiopaque material.
(38) The medical device of (37) in combination with one or more or any combination of (a) to (i):
(a) wherein the outermost proximal ring is adjoined to the first proximal ring only by the first proximal links, wherein two of the first proximal links extend parallel to the axis a-a and have a constant cross-sectional moment of inertia;
(b) wherein the outermost distal ring is adjoined to the first distal ring only by the first distal links, each of which is a non-linear link strut;
(c) wherein the proximal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of a W crown and a Y crown with the first proximal ring;
(d) wherein the first distal ring and the second distal ring are adjoined by a distal marker link;
(e) wherein the distal marker link comprises a structure surrounding two apertures and the first distal ring and the second distal ring are additionally adjoined by one or two marker links;
(f) wherein the distal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the first distal ring and the other of a W crown and a Y crown with the second distal ring, wherein the W crown is wider than the Y crown;
(g) wherein the proximal marker link further comprises: an edge substantially surrounding the hole and defining a hole wall and a brace bar edge, wherein a distance between the wall and the edge is D; a radiopaque marker disposed in the hole, the marker including a head having a flange disposed on a rim; wherein the flange has a radial length between 1/2D and less than D; wherein the thin-walled stent thickness (t) is related to the length (L) of the marker measured between the distal and inner luminal surfaces of the marker by 1.1 ≦ (L/t ≦ 1.8;
(h) wherein the distal marker link forms one of a W crown and a Y crown with the first distal ring and the other of a W crown and a Y crown with the second distal ring, wherein a 1/2 wavelength of the ring with the W crown measured from the W crown to the first adjacent crown is greater than a 1/2 wavelength of the ring with the Y crown; and
(i) wherein the length of the first proximal link is less than the length of the first distal link, and/or the length of the second distal link is less than the length of the first distal link.
(39) A medical device, comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; a thin-walled stent crimped to the balloon, the thin-walled stent having a proximal portion and a distal portion formed from a web of rings interconnected by links of the thin-walled stent, wherein each ring has a plurality of crowns, including a U crown and at least one of a Y crown and a W crown, each ring extending circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); the proximal portion crimped to the proximal balloon end includes an outermost proximal ring adjoined to the first proximal ring by a first proximal link, and the first proximal ring adjoined to the second proximal ring by a second proximal link; the distal portion crimped to the distal balloon end comprises an outermost distal ring adjoined to a first distal ring by a first distal link and a first distal ring adjoined to a second distal ring by a second distal link; wherein-the first proximal link comprises a proximal marker link comprising a proximal aperture comprising a radiopaque material, -the first distal link is free of a link holding a radiopaque material, and-the first distal link comprises a non-linear link; wherein the thin-walled stent has an outer diameter of about D-min; and wherein D-min ═ 1/pi × [ (n × strut _ width) + (m × link _ width) ] +2 × t.
(40) The medical device of (39) in combination with one or more or any combination of (a) to (i):
(a) wherein the outermost proximal ring abuts the first proximal ring only through the first proximal links, each first proximal link extending parallel to axis a-a and having a constant cross-sectional moment of inertia;
(b) wherein the non-linear link is a U-shaped link;
(c) wherein the proximal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of the W crown and the Y crown with the first proximal ring, and wherein the marker link includes a structure surrounding a bore;
(d) wherein a first link portion of the proximal marker link extends from the W-crown to the structure and a second link portion of the proximal marker link extends from the Y-crown to the structure, wherein the first link portion length is greater than the second link portion length;
(e) wherein the first link portion length is approximately equal to the sum of twice the ring width and the strut length extending between the U crown and U, Y or W crown of the ring.
(f) Wherein the non-linear link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of a W crown and a Y crown with the first proximal ring, and wherein the non-linear link includes a U-shaped structure between the W crown and the Y crown;
(g) wherein a first link portion of the proximal U-shaped link extends from the W-crown to the U-shaped structure and a second link portion of the proximal marker link extends from the Y-crown to the structure, wherein the first link portion length is greater than the second link portion length;
(h) wherein the first link portion length is approximately equal to the sum of twice the ring width and the strut length extending between the U crown and U, Y or W crown of the ring; and
(i) wherein the distal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the first distal ring and the other of a W crown and a Y crown with the second distal ring.
(41) A medical device, comprising: a thin-walled stent having a proximal portion and a distal portion formed by a web of rings interconnected by links of the thin-walled stent, wherein each ring has a plurality of crowns, including a U crown and at least one of a Y crown and a W crown, each ring extending circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); the proximal portion comprises an outermost proximal ring adjoining the first proximal ring by a first proximal link, and the first proximal ring adjoins the second proximal ring by a second proximal link; the distal portion including an outermost distal ring adjoined to the first distal ring by a first distal link, and the first distal ring adjoined to the second distal ring by a second distal link; wherein the first proximal link comprises a proximal marker link comprising a pair of proximal apertures comprising a radiopaque material, wherein the proximal apertures are aligned along axis a-a, and the first distal link comprises a distal marker link comprising a pair of distal apertures comprising a radiopaque material, wherein the distal apertures are aligned along axis B-B.
(42) The medical device of (41) in combination with one or more or any combination of (a) to (i):
(a) wherein the outermost proximal ring abuts the first proximal ring only through the first proximal links, wherein two of the first proximal links extend parallel to the axis a-a and have a constant cross-sectional moment of inertia;
(b) wherein the outermost distal ring abuts the first distal ring only through the first distal marker link and the non-linear link strut;
(c) wherein the proximal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of a W crown and a Y crown with the first proximal ring;
(d) wherein the width of the W crown formed by the first end is greater than the width of the Y crown formed by the second end such that the wavelength of the ring forming the W crown is longer than the wavelength of the ring forming the Y crown;
(e) wherein the distal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost distal ring and the other of a W crown and a Y crown with the first distal ring;
(f) wherein the distal marker link has a first link portion extending from the aperture to the W crown and a second link portion extending from the aperture to the Y crown, wherein the first link portion has a length that is longer than a length of the second link portion;
(g) wherein the proximal marker link further comprises: an edge substantially surrounding the hole and defining a hole wall and a brace bar edge, wherein a distance between the wall and the edge is D; a radiopaque marker disposed in the hole, the marker including a head having a flange disposed on a rim; wherein the flange has a radial length between 1/2D and less than D; wherein the thin-walled stent thickness (t) is related to the length (L) of the marker measured between the distal and inner luminal surfaces of the marker by 1.1 ≦ (L/t ≦ 1.8;
(h) wherein the radiopaque material is received within the hole and the radiopaque material has the shape of a frustum; and
(i) the aperture includes first and second openings on the first and second sides of the marker link, respectively, wherein the first opening is larger than the second opening and the frustum is substantially flush with the first and second openings.
(43) A medical device, comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; a thin-walled stent crimped to the balloon, the thin-walled stent having a proximal portion and a distal portion formed from a web of rings interconnected by links of the thin-walled stent, wherein each ring has a plurality of crowns, including a U crown and at least one of a Y crown and a W crown, each ring extending circumferentially in an undulating fashion along a vertical axis (B-B) perpendicular to the longitudinal axis (a-a); the proximal portion crimped to the proximal balloon end includes an outermost proximal ring adjoined to a first proximal ring by a first proximal link and the first proximal ring adjoined to a second proximal ring by a second proximal link; the distal portion crimped to the distal balloon end includes an outermost distal ring adjoined to a first distal ring by a first distal link, and the first distal ring adjoined to a second distal ring by a second distal link; wherein (1) the first proximal link comprises a proximal marker link comprising a structure extending parallel to axis a-a and comprising a radiopaque material, (2) the first distal link strut comprises a distal marker link comprising a structure extending parallel to axis B-B and comprising a radiopaque material; wherein the thin-walled stent has an outer diameter of about D-min; and wherein D-min ═ 1/pi × [ (n × strut _ width) + (m × link _ width) ] +2 × t.
(44) The medical device of (43) in combination with one or more or any combination of (a) to (i):
(a) wherein the outermost proximal ring abuts the first proximal ring only through the first proximal links, each first proximal link extending parallel to axis a-a and having a constant cross-sectional moment of inertia;
(b) wherein the first distal link comprises a non-linear link;
(c) wherein the proximal marker link has a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of a W crown and a Y crown with the first proximal ring, and wherein the marker link includes structure surrounding an aperture;
(d) wherein a first link portion of the proximal marker link extends from the W crown to the structure and a second link portion of the proximal marker link extends from the Y crown to the structure, wherein a length of the first link portion is greater than a length of the second link portion.
(e) Wherein the first link portion length is approximately equal to the sum of twice the ring width and the length of the strut extending between the U-crowns and Y, U or W-crowns of the ring;
(f) wherein the first distal link comprises a non-linear link having a first end and a second end, the first end forming one of a W crown and a Y crown with the outermost proximal ring and the other of a W crown and a Y crown with the first proximal ring, and wherein the non-linear link comprises a U-shaped structure between the W crown and the Y crown;
(g) wherein a first link portion of the non-linear link extends from the W crown to the U-shaped configuration and a second link portion of the non-linear link extends from the Y crown to the U-shaped configuration, wherein a length of the first link portion is greater than a length of the second link portion;
(h) wherein the first link portion length is approximately equal to the sum of twice the ring width and the length of the strut extending between the U-crowns and Y, U or W-crowns of the ring;
(i) wherein the aperture of the distal marker link is located between and without overlap or underlap between the U-crown adjacent the W-crown of the outermost distal ring and the U-crown adjacent the Y-crown of the first distal ring.
Incorporation by reference
All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. In the event of any inconsistent word and/or phrase usage between an incorporated publication or patent and this specification, such word and/or phrase will have a meaning consistent with the manner in which it is used in this specification.
Drawings
Fig. 1 is a perspective view of a portion of a prior art stent. The stent is shown in a crimped state (balloon not shown).
Fig. 2 is a top partial view of a stent showing a marker link having a hole for holding a radiopaque material and connecting adjacent rings.
Fig. 2A is a reproduction of fig. 2 showing additional dimensional features and/or characteristics of a linkage for holding two markers.
FIG. 2B illustrates an alternative embodiment of a marker link.
Fig. 2C is another reproduction of fig. 2 with a marker attached to the linkage.
FIG. 3 illustrates a distal portion and a proximal portion of a stent according to one embodiment. These end portions include the marker links of fig. 2 connected to the ring.
Fig. 3A shows a section IIIA of the stent of fig. 3.
Fig. 3B shows a section IIIB of the stent of fig. 3.
Fig. 3C shows the stent of fig. 3 in a crimped state.
Fig. 3D shows the stent of fig. 3 crimped to a balloon of a balloon catheter.
Fig. 4 shows an end portion of a stent according to another embodiment. The end portion includes a link connecting adjacent rings and containing a marker. These rings have a W crown formed in part by the marker link. The W crown is modified to accommodate the tag structure.
Fig. 4A shows a section IVA of the stent of fig. 4.
Fig. 4B shows the loop of the distal end of the stent of fig. 3, the loop of the distal end of the stent of fig. 4 being shown in phantom to illustrate the difference between the two loops.
Fig. 4C shows a section IVC of the stent of fig. 4.
Fig. 4D shows the stent of fig. 4 in a crimped state.
Fig. 5 is a partial view of a distal portion of a stent according to another embodiment.
Fig. 6 shows an end portion of a stent according to another embodiment. The distal portion is different from the proximal portion. A non-linear link strut connects the outermost distal rings with the inner rings and a marker link is located between the inner rings at the distal end portion.
Fig. 6A is a partial view of the stent of fig. 6 in a crimped state.
Fig. 6B is an image of the distal end of the catheter in a curved configuration, showing the distal loop of the stent flaring or protruding outward from the distal end of the balloon.
Fig. 6C is an image of the distal end of the catheter in a curved configuration, fig. 6C showing the distal loop of the stent according to fig. 6. When the catheter is placed in a curve, the distal loop no longer expands outwardly.
Fig. 7 shows an end portion of a stent according to another embodiment. The proximal portion is different from the distal portion. A non-linear link strut and a modified marker link connect the outermost distal ring with the inner ring.
Fig. 7A is a partial view of the stent of fig. 7 in a crimped state.
Fig. 7B is a partial view of the stent of fig. 7 taken at section VII in fig. 7.
Fig. 7C is an image of the distal end of the catheter in a curved configuration, showing the distal loop of the stent according to fig. 7. The distal loop does not expand outwardly when the catheter is placed in a curve.
Fig. 8A-8B show side and top views, respectively, of a marker according to another embodiment.
Fig. 9 is a cross-sectional view of a rod having a bore and the marker of fig. 8A-8B embedded in the bore.
Fig. 10 is a lateral cross-section of a first die for forming a rivet marker with a radiopaque bead.
Figure 11A is a side view of a rivet marker formed using the die of figure 10.
Fig. 11B is a side cross-section of a stent strut with the marker of fig. 11A engaging the aperture of the strut and deforming the marker after the molding process so that the upper and lower edges retain the marker in the aperture.
Fig. 12 is a lateral cross-section of a second die for forming a rivet marker with a radiopaque bead.
Fig. 13 is a side view of a staking marker formed using the die of fig. 12.
Fig. 14A, 14B, and 14C are perspective views depicting aspects of a process for deforming rivets embedded in stent holes to strengthen their engagement with the holes against displacement forces associated with crimping or balloon expansion.
Fig. 15A is a side cross-sectional view of a deformed rivet marker and a stent hole after the process described in connection with fig. 14A-14C.
Fig. 15B is a view of the deformed marker shown in fig. 15A.
FIG. 15C is a side cross-sectional view of the rivet and tag hole of FIG. 15A after a heating step.
Figures 16A-16C illustrate the steps associated with removing a formed rivet marker from a die and placing the rivet marker in a hole in a stent.
Fig. 17A and 17B depict a process of crimping a thin-walled stent according to the present disclosure.
Detailed Description
In the description, like reference numerals appearing in the figures and description indicate corresponding or identical elements in the different views.
For purposes of this disclosure, the following terms and definitions apply:
the terms "about," "approximately," "generally," or "approximately" refer to less than, or greater than 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, between 1-2%, between 1-3%, between 1-5%, or less than or greater than 0.5% -5% of a set point, range, or each end point of a set range, or one sigma (sigma), two sigma, three sigma (gaussian distribution) from a set average or desired value. For example, a d1 of about d2 means that d1 differs from d2 by 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0%, or 1-2%, 1-3%, 1-5%, or 0.5% -5%. If d1 is an average value, then d2 is approximately d1 means that d2 is within one sigma, two sigma or three sigma variances or standard deviations of d 1.
It will be understood that any numerical value, range, or any range endpoint (including, for example, "approximately free", "approximately all", etc.) prefixed with the word "about", "approximately", "generally" or "approximately" in this disclosure also describes or discloses the same numerical value, range, or any range endpoint without the word "approximately", "generally" or "approximately".
"glass transition temperature", TG, refers to the temperature at which an amorphous domain of a polymer changes from a brittle, glassy state to a strong, deformable or ductile state at atmospheric pressure. This application defines TG of polymers and methods of finding TG or TG-low (lower end of TG range) in the same manner as in US application No.14/857,635 (attorney docket number: 62571.1216).
"stent" refers to a permanent, permanent or non-degradable structure, typically composed of a non-degradable metal or metal alloy structure, while "stent" refers generally to a temporary structure comprising a bioresorbable or biodegradable polymer, metal, alloy or combination thereof and capable of radially supporting a blood vessel for a limited period of time (e.g., 3,6 or 12 months) after implantation. However, it should be understood that the term "inner support" is sometimes used in the art when referring to either type of structure.
"expanded diameter" or "expanded diameter" refers to the inner or outer diameter that a stent reaches when its support balloon is inflated to expand the stent from its crimped configuration to implant the stent within a vessel. The inflated diameter may refer to an inflated balloon diameter that exceeds a nominal balloon diameter, for example a 6.5mm balloon (i.e., a balloon having a nominal diameter of 6.5mm when inflated to a nominal balloon pressure, such as 6 times atmospheric pressure) has an inflated diameter of about 7.4mm, or a 6.0mm balloon has an inflated diameter of about 6.5 mm. The ratio of the nominal to inflated balloon may be in the range of 1.05-1.15 (i.e., the inflated diameter may be 5% -15% larger than the nominal inflated balloon diameter). After the scaffold diameter is reached by balloon pressure, the scaffold diameter will decrease to some extent due to recoil effects that are primarily related to any or all of the manner in which the scaffold is manufactured and processed, the scaffold material, and the scaffold design.
When referring to a diameter, it shall refer to an inner or outer diameter unless otherwise specified or implied in the context of the specification.
When referring to a stent strut, it is also applicable to a link or a bar arm.
The "post-expansion diameter" (PDD) of a stent refers to the inner diameter of the stent after it has been increased to its expanded diameter and the balloon removed from the patient's vessel. PDD causes a kickback effect. For example, acute PDD refers to the stent diameter that causes acute recoil in the stent.
By "pre-crimp diameter" is meant the Outer Diameter (OD) of the tube from which the stent is made (e.g., cut from a dip-coated, injection molded, extruded, radially expanded, drawn and/or annealed tube) or the Outer Diameter (OD) of the stent prior to its crimping onto the balloon. Similarly, "crimped diameter" means the OD of the scaffold when it is crimped onto a balloon. The "pre-crimp diameter" may be about 2 to 2.5, 2 to 2.3, 2, 2.5, 3.0 times greater than the crimp diameter and about 0.9, 1.0, 1.1, 1.3 times, and about 1-1.5 times greater than the expanded diameter, nominal balloon diameter, or post-inflation diameter. For the purposes of this disclosure, crimping means a reduction in diameter of a stent characterized by significant plastic deformation, i.e., more than 10% or more than 50% reduction in diameter is due to plastic deformation, as in the case of an inner stent or stent having an undulating ring pattern (e.g., fig. 1), at the crowns. When the stent is deployed or expanded by the balloon, the inflated balloon plastically deforms the stent from its crimped diameter. A method for crimping a stent made according to the present disclosure is described in US20130255853 (attorney docket No. 62571.628).
Poly (L-lactide) or PLLA materials that "comprise" or "have" include, but are not limited to, PLLA polymers, blends or mixtures comprising PLLA and another polymer, and copolymers of PLLA and another polymer. Thus, a strut comprising PLLA means that the strut may be made from any of a material comprising PLLA polymer, a blend or mixture comprising PLLA and another polymer, and a copolymer of PLLA and another polymer.
Bioabsorbable stents comprised of biodegradable polyester polymers are radiolucent. To provide fluoroscopic visualization, radiopaque markers are placed on the stent. For example, the stent described in U.S. patent No.8,388,673 (the '673 patent) has two platinum markers fixed at each end of the stent 200, as shown in fig. 2 of the' 673 patent.
When referring to a direction perpendicular or parallel to the axis a-a (e.g., as shown in fig. 3), it is meant a direction perpendicular or parallel to the axis of the stent or tube. Similarly, when referring to a direction perpendicular or parallel to axis B-B (e.g., as shown in FIG. 3), it is meant perpendicular or parallel to the circumferential direction of the stent or tube. Thus, the sinusoidal rings of the stent extend parallel (in a periodic manner) to the circumferential direction or to axis B-B and perpendicular to axis A-A, while in one embodiment the links extend parallel to the axial direction or axis A-A of the stent or tube and perpendicular to axis B-B.
In any event where the same element numbers are used in more than one figure, it should be understood that the same description used for the elements first in the first figure applies to the embodiments described in the subsequent figures unless otherwise noted.
The dimension of the thickness (e.g., wall, strut, ring, or link thickness) refers to the dimension measured perpendicular to the axes a-a and B-B. The width dimension is measured in the plane of the axes A-A and B-B; more specifically, the width is the cross-sectional width from one side of the continuous structure to the other; thus, the U-shaped link 636 has a constant link width over its length, just as the link 334 has a constant link width. Furthermore, it should be understood that the planes of the so-called axes A-A and B-B are technically not planar, as they describe the surface of a tubular structure having a central lumen axis parallel to the axis A-A. Thus, if the stent position is described in a cylindrical coordinate system (i.e., axis a-a is the Z-axis and the position of the luminal/abluminal surface of the crown, link, ring, etc. is derived from the angular and polar constants), axis B-B may thus alternatively be considered the angular component.
"thin-walled thickness", "thin-walled stent", "thin-walled" refers to a strut, ring, link or bar arm made of a polymer comprising poly (L-lactide) and having a wall thickness of less than 125 microns. Challenges faced when using thin-walled stents are discussed herein, including securing markers of radiopaque material having the same volume.
Fig. 2 is a top plan view of a portion of a polymer stent (e.g., a polymer stent having a pattern of rings interconnected by links). In fig. 2, marker link 20 ("link 20") extends between ring 312a and ring 321 b. The link 20 forms left and right structures or strut portions 21b, 21a, respectively, for holding radiopaque markers. The tag can be retained in the hole 22 formed by the structures 21a, 21 b. Surface 22a corresponds to the distal luminal surface of the stent.
Fig. 2A is a reproduction of fig. 2 showing additional dimensional features, particularly the characteristic dimensional features D0, D1, and D2. The diameter of the hole 22 is D0. The distance between adjacent holes 22 is greater than or equal to D1. And the width of the edge of one or both of the holes 22, or the distance from the inner wall surface surrounding one or both of the holes 22 to the edge of the connecting rod 20, is greater than or equal to D2.
FIG. 2B illustrates the dimensional features described in relation to FIG. 2A for marker link 720 oriented such that structures 21a, 21B are offset along axis B-B opposite axis A-A. Marker 720 connects ring 312a and ring 312 b. Figure 7 shows a stent embodying the marker.
FIG. 2C shows rivet-type markers 127 '/137' secured in the hole 22. The dimensions shown refer to parameters that may be used to monitor the marker link (after radiopaque attachment) to assess its ability to resist forces tending to displace the rivets 127 '/137' from the hole 22. This displacement force may result from the deformation of the surface of the balloon under pressure or nearby stent structures that tend to deform the holes 22, such as when the stent is crimped or expanded by the balloon. According to one aspect, the rivet head and/or tail of the rivet 127 '/137' pair may be monitored to determine if the minimum distances δ 1, δ 2, and δ 3 are met (fig. 2C). Distances δ 1, δ 2 and δ 3 reflect one or two minimum dimensions of the head and/or tail of the rivet pressed into the hole, which indicates both that the rivet should remain in the hole 22 (if the diameter of the head or tail is too small, it is equally unable to resist the displacement force) and that the excess rivet material does not cause problems such as balloon puncture or vessel irritation when the stent is implanted in a vessel. According to embodiments, the minimum distance δ 2 from the end of the tag head/tail to the edge of the strut (or link) portion 21a/21b may be about 10%, 25% and up to 50% of D2. Over 50% means that the head or tail is too small to hold the rivet in place. For a cephalad/caudal equal to or greater than D2, the cephalad may or does extend to the edges of the struts/linkages, which may cause problems such as the formation of relatively sharp edges that may damage the balloon or irritate adjacent tissue. The minimum distance between the tag head/tail (i.e., δ 1) is 0 or up to 25% of the distance D1. This may exceed the maximum height required for the struts (about 160 microns) if the edges or heads of the markers overlap each other. The minimum length (i.e., δ 3) that the head/tail extends to the right or left of the hole 22 is greater than 50% of D2.
Methods for inserting radiopaque markers into holes typically rely on cylindrical holes to retain the marker. The majority of the retention force comes from the friction between the wall and the marker material. In this way, the marker material is reliably retained in the stent pores when the stent has a wall thickness of 150 microns and above. However, when the wall thickness is reduced to 100 microns or less than 100 microns, it becomes more challenging to retain the marker material in the hole. While coating materials for carrying drugs may help hold the markers in place, these coatings (e.g., Everolimus/PDLLA) tend to be very thin-on the order of 3 microns, which limits its out-of-plane shear strength that prevents displacement of the markers from the holes.
For stent struts, the reduction in wall thickness may result in some desirable characteristic or property. Advantages of using reduced wall thickness include a smaller profile and thus better delivery, reduced acute clotting activity, and potentially better healing. In some embodiments, for stents with thinner struts, it is desirable to use markers of the same size so that there is no difference or reduction in radiopacity between the two stent types. However, reducing the strut thickness while maintaining the same size of the marker aperture 22 may result in the marker protruding above and/or below the strut surface due to the reduced aperture volume. It is desirable to keep the distal and luminal surfaces 25a, 25b of the marker flush with the respective luminal and distal surfaces of the struts, in which case the diameter (d) of the bore 22 can be increased to partially account for the reduced bore volume caused by thinner struts.
Paragraphs [0073] to [0083] of US application serial No.14/738,710, which is co-owned with the present application, describe factors that affect the ability of the stent to retain markers in the hole and special challenges faced when the wall thickness is less than 160 microns or 125 microns. According to some embodiments, it has been found that when the wall thickness is less than 125 microns (when the stent is thin walled), the marker cannot be reliably held in the hole substantially by friction alone. In a preferred embodiment with a wall thickness of less than 100 microns, the marking material is retained in the hole using a rivet-shaped marker, which is briefly discussed above in connection with fig. 2C and described in more detail in connection with fig. 8-16.
Embodiments of stent patterns suitable for meeting one or a combination of the following goals are described below:
(i.) for thin-walled stents carrying radiopaque markers, reduced crimping profile,
(ii.) affixing radiopaque markers in the thin-walled stent,
(iii) reducing strain energy buildup in the marker-retaining structure when the thin-walled stent is deformed during crimping, balloon expansion, or delivery of the stent to the target site at the target vessel site, and
(iv) for a thin walled stent or a stent comprising PLLA and having a wall thickness greater than 125 microns, the protrusion or expansion of the end annulus is avoided at the distal end of the stent.
It should be understood that the above objects are interrelated and that more than one object may be resolved by a single change. For example, goals (iii) and (iv) may be met by making the marker linkage more flexible. Stents according to these embodiments may be made from thin-walled tubes or sheets comprising poly (L-lactide) (PLLA) material that are laser cut from a tubular body to create the patterns in fig. 3-7. The process of making the tube may include one or more of extrusion, injection moulding, solid phase processing and biaxial stretching as described in US 14/810344 (62571.1212).
A stent according to embodiments (e.g., stent 300, 400, 500, 600 or 700) is preferably crimped to a balloon catheter, such as the one shown in fig. 3D. The scaffold may be attached to the balloon using any of the crimping processes described in US20130255853 to ensure the desired crimp diameter, for example D-min (defined below); in particular, any of the crimping processes and devices for crimping described in paragraphs [0068] - [0073], [0077] - [0099], [0111] - [0126], [0131] - [0146] of US20130255853 and fig. 1A, 1B, 4A, 4B, 5A, 5B, 8A and 8B.
Fig. 3 illustrates a partial plan view of an end portion of a stent or stent 300 according to one embodiment. The left or distal portion 302 (i.e., the left side of fig. 3) includes sinusoidal rings 312a, 312b, and 312c, where ring 312a is the outermost ring. The loop 312a and the loop 312b are adjoined by two links 334 and the marker link 20. The ring 312c and the ring 312b are adjoined by three links 334 parallel to the axis a-a. The link 334 extends parallel to the axis a-a and has a constant cross-sectional moment of inertia over its length, meaning that the link 334 has a constant width and thickness and the position of the centroid or geometric center (or longitudinal axis) of the link is everywhere parallel to the axis a-a. Right or proximal portion 304 (i.e., the right side of fig. 3) includes sinusoidal rings 312d, 312e, and 312f, where ring 312f is the outermost ring. The ring 312d and the ring 312e are adjoined by three links 334. The loop 312e and the loop 312f are adjoined by two links 334 and the marker link 20. Thus, the stent 300 has marker links 20 extending between and abutting the outermost link and the adjacent inner ring. The stent 300 may have 15, 18, or 20 rings 312 connected to each other by links 334.
The ring 312 (e.g., ring 312B) is sinusoidal in the sense that the curvature of the ring along axis B-B is best described by a sine wave having a wavelength equal to the distance between adjacent peaks 311a of the ring. The rings have a constant width at crowns 307, 309, and 310 and struts 330 connecting the crowns to adjacent crowns.
There are three crown types in each inner ring 312b through 312 e: u-crown, Y-crown and W-crown. The outermost rings are only of the Y-crown type or the W-crown type, and of the U-crown type. The peaks or crests 311a (or troughs or valleys 311b) may correspond to U-crowns, Y-crowns, or W-crowns. For the outermost ring 312a, there are only a U-crown type and a W-crown type. For the outermost ring 312f, there are only a U-crown type and a Y-crown type. Marker link 20 abuts the rings by forming a W-crown with a first ring (e.g., ring 312e) and a Y-crown with a second ring (e.g., ring 312 f).
Link 334 is connected to ring 312f at Y-crown 310. "Y-crown" means a crown that extends at an obtuse angle (greater than 90 degrees) between the struts 330 and the links 334 of the ring 312. Link 334 is connected to ring 312a at W-crown 309. "W-crown" means a crown in which the angle extending between brace 330 and link 334 is acute (less than 90 degrees). The U-crown is the crown to which no link is connected. Marker link 20 is connected to the ring at W-crowns 314 and Y-crowns.
For stent 300, there are 6 peaks or crests 311a and 6 troughs or valleys 311b for each ring 312. The peak 311a always follows a valley 311 b. Ring 312b is made up of 12 crowns: 3 are W-crowns 309, 3 are Y-crowns 310 and 6 are U-crowns 307.
Fig. 3A and 3B show partial close-up views of the bracket 300. Fig. 3A shows the IIIA section of fig. 3 and fig. 3B shows the IIIB section of fig. 3. The following description with respect to fig. 3A-3B applies equally to portions 302 and 304 of stent 300, it being understood that in the case of link 20, it is connected with outermost ring 312 at Y-crown 316 and abuts ring 312e at W-crown 314.
Referring to fig. 3A, the continuous wavelength of the outermost ring 312a has lengths L1 and L2, or the distance from crown 314 to U-crown 307 (along axis B-B) is L1 and the distance from U-crown 307 to Y-crown 309 is L2. The same applies to ring 312 b-the distance from crown 316 to W-crown 309 and the distance from W-crown 309 to Y-crown 310 being L1 and L2, respectively. For the stent 300, L1-L2-constant for the rings 312a, 312 b. That is, the distance or wavelength from one peak to another is the same. Likewise, for stent 300, L1+ L2 is constant throughout; that is, the distance between the W-crowns and the Y-crowns is the same for all rings, as is the distance between adjacent peaks for rings 312a through 312 f. Distance X in fig. 3A refers to the half period or half length of the sine wave, or 1/2 of L1. The distance X is equal to the distance from the crown 314 to the U-crown 307 adjacent the crown 312 a. For ring 312b, X is the same. In another embodiment, L1 is not equal to L2 and X is different between the outermost ring 312a and the adjacent ring 312 b.
In alternative embodiments including the stents 400, 500 or 700 described below, the rings may have a serrated, rather than sinusoidal, ring shape. An example of a serrated ring appears in figures 5A and 6A of US 20140039604. A serration ring can be described as a non-curved strut element converging at a crown shaped to have an inner crown radius and an outer crown radius. The same description applies, meaning that the ring can be described in terms of wavelength, struts, and crowns, except that the shape is not sinusoidal but rather saw-toothed. The term "undulating" refers to sawtooth ring types and sinusoidal ring types.
Referring to FIG. 3B, the distance along axis A-A from the peak or apex of loop 312a to the peak or apex of the adjoining loop 312B, or the length of marker 20 (plus width t1) is A12. The distance along axis a-a from the peak or apex of loop 312b to the peak or apex of the adjacent loop 312c, or the length of marker 334 between the loops (plus width t2) is a 23. For stent 300, a12 ═ a 23. The width of link 20 to the left side of marker structure 21a is tm1 and the width of marker link 20 to the right side of structure 21b is tm 2. The width of link 334 is tl. The crowns 307, 310, 309 and 314 and struts 330 of ring 312a have a constant width t 1. The crowns 307, 310, 309 and 314 and struts 330 of ring 312b have a constant width t 2. The crowns 307, 310, 309 and 314 and struts 330 of ring 312c have a constant width t 3. For stent 300, t1 is less than t3 and t2 is t 3. The dimensions B1 and B2 refer to the surfaces of the crowns of rings 312a and 312c, respectively, that extend parallel to the axis B-B or are portions of the crown surface that are not curved (i.e., flat). For stent 300, B1 ═ B2.
Referring to fig. 3C, stent 300 with marker 20 in a crimped state is shown. The crimp diameter imposed on stent 300 is the theoretical minimum crimp diameter in which struts that converge in the same crown are connected to one another when the stent is fully crimped (i.e., when the stent is removed from the crimping device, or when the stent is placed in a retaining sheath shortly after crimping). The equation for the theoretical minimum curl diameter (D-min) under these conditions is shown below
D-min=(1/π)×[(n×strut_width)+(m×ink_width)]+2*t
Wherein the content of the first and second substances,
"n" is the number of struts in the ring (12 struts for stent 300),
"strut width" is the width of the strut (170 microns for stent 300),
"m" is the number of links (3 for stent 300) that abut the adjacent ring,
"ink _ width" is the width of the link (127 microns for the stent 300), and
"t" is the wall thickness (93 microns for stent 300).
Thus, for stent 300, D-min ═ 1/pi × [ (12 × 170) + (3 × 127) ] +2 × (93) ═ 957 microns.
With the pair of abutment rings 312a and 312B at distal end 302 and the pair of abutment rings 312e and 312f at the distal end, marker link 20 is wider (along axis B-B) than link 334 to accommodate the marker. Thus, adjacent struts 330 may often overlap with links 20 to achieve the same D-min at all times. This situation is depicted in fig. 3C. This state of the crimped stent raises concerns about the local strength of the ring and the links holding the markers. As shown in fig. 3C. There may be overlap (struts pressing against the distal luminal surface of the marker) or partial overlap (struts pressing against the luminal surface of the marker) by struts 330a, 330b and/or associated U-crowns associated with these struts. This overlap/underlap is preferably eliminated when the stent is crimped.
Stent struts, particularly thin-walled stent struts and links, are not designed to twist or undergo significant torsion. Twisting can occur when the struts abut and overlap each other. When a stent strut has a higher aspect ratio of width to thickness, it is more prone to twisting for a strut when it abuts an adjacent structure, such as structure 21a of marker link 20 (a thinner-walled stent has a higher aspect ratio for the same vascular tissue coverage-strut width than a thicker-walled stent). As can be seen from the deformed state of fig. 3C compared to fig. 3, a twist is introduced into the ring structure and possibly also into the connecting struts. This type of abnormal deformation may lead to crack propagation or reduced fatigue life of the ring and/or the linkage 20 when the balloon is expanded in a blood vessel.
Fig. 3D shows a medical device including a balloon catheter and a scaffold 300 crimped to balloon 15. Distal end 302 of stent 300 is closest to distal end 17b of balloon 15 and proximal end 304 is closest to balloon proximal end 17 a. The tip or distal-most end 12 of the balloon catheter is shown. A guidewire or mandrel 8 extends from the tip 12, exiting from the lumen of the catheter shaft 2. The scaffold crimped to the balloon (according to D-min or other minimum crimp diameter) may be scaffold 300 or scaffold 400, discussed below. Brackets 500, 600, and 700 may also be used in place of bracket 300.
As previously mentioned, thin-walled stents with similar stent patterns were found to exhibit significantly higher incidence of strut overlap or partial overlap (hereinafter referred to as MBOL) similar to that shown in fig. 3C compared to stents with thicker wall thicknesses, such as the stent described in US2010/0004735 or the ABSORB GT1 bioabsorbable stent. Higher MBOL incidence is more likely to occur when the width of the links containing the marker is widened to accommodate the same overall volume of marker material used in stents with struts of higher wall thickness. MBOL may also be higher when a more aggressive crimp is used (e.g., D-min crimp profile).
Furthermore, when attaching the same volume of marker beads to both thin and thick walled stents and aligning the marker with the distal and inner luminal surfaces of the linkage rod, the marker bead region must assume a flatter and wider shape that deforms the structures 21a and 21b to increase the tendency of the struts to overlap in the marker bead region (as shown in fig. 3) because the marker structures 20, 21a, 21b have a higher aspect ratio in order to retain the desired amount of radiopaque material in the thinner linkage rod. And/or may have residual strain during swaging of the marker, which makes it easier for the marker structure 21a, 21b to distort out of plane. Table 1 summarizes these findings.
Figure GDA0002576218240000171
Figure GDA0002576218240000181
Paragraphs [0073] to [0083] of U.S. application serial No.14/738,710, which is commonly owned by the same inventor as the present application, describe factors that affect the ability of the stent to retain markers in the hole and special challenges that are faced when the wall thickness is less than 160 microns or less than 125 microns. In addition, the' 710 application explains how the marker retention structure must be wider for reduced wall thickness and the same radiopaque material volume (thus, higher aspect ratio and greater tendency for twisting motion and overlap during crimping) if the marker is to be flush with the distal luminal surface of the strut as needed. The wider and flatter marker structure increases the Aspect Ratio (AR) of the link width to its wall thickness, which increases the likelihood of the link twisting when in contact with an adjacent strut or crown.
In one example, the Aspect Ratio (AR) of the marker link of a thin-walled stent with a 93 micron wall thickness is about 4.5(AR ═ ts/t ═ 419 microns/93 microns ═ 4.5) compared to a stent with a thicker wall thickness of 158 microns (as described in US 2010/0004735) and the same volume of marker material held by the 93 micron and 158 micron marker structures. For a stent having a total thickness of 158 microns, the AR is about 2(AR ts/t 322/158). Thus, for the same volume of marking material and reduction of wall thickness from 158 microns to 93 microns, the AR increases by a factor of 2.5. In view of the significant increase in aspect ratio, it is understood that for thin-walled stents, there is a greater chance that the thin-walled marker link will distort when in contact with an adjacent strut or crown during crimping, and/or that the strut will have a greater chance of overlapping/partially overlapping the marker link.
It is well known that during crimping, the stent bar arm angle decreases and the adjacent bar arm struts naturally move toward the links of the w crowns. During this crimping event, the w-crown's outside radius and the center point of the outside radius (typically located outside the link) play an important role in guiding stent strut crimping. In fact, the center point of the outside radius is intended to be the pivot point that guides the initial behavior of the strut and limits the range of strut movement to the marker link feature. In a second aspect, the MBOL present between the strut and marker link features is closely related to the outside radius and pivot point location. In the case of a w-crown with marker link 20 and thin-walled stent design, the center point of the w-crown is initially located within marker structure 21. Thus, during crimping, strut closing behavior is not kinematically constrained, resulting in frequent overlap/partial overlap with marker links. To reduce the incidence of MBOL, the center point of the W crown with marker structure 21 may be moved to a region outside the range of marker structure 21. Thus, during crimping, as the strut of the w-crown moves toward the marker structure 21, the strut should avoid being squeezed into and sliding into an overlapping or partially overlapping state that causes twisting in the w-crown and/or the link.
Fig. 4 shows a partial plan view of an end portion of a stent or stent 400 according to another embodiment. Left side or distal portion 402 (i.e., left side of fig. 4) includes sinusoidal rings 412a, 312b, and 312c, where ring 412a is the outermost ring. Ring 412b and ring 312c are adjoined by two links 334 and marker link 20. The rings 312b and 312c are adjoined by three links 334 that extend parallel to the axis a-a. Right or proximal portion 404 (i.e., right side of fig. 4) includes sinusoidal rings 312d, 412b, and 312f, where ring 312f is the outermost ring. Ring 312d and ring 412b are adjoined by three links 334. Ring 412b and ring 312f are adjoined by two links 334 and marker link 20. Thus, the stent 400 has marker links 20 that extend between and will abut the outermost link with the adjacent ring at the outermost link 20. The stent 400 may have 15, 18, or 20 rings 312 connected to each other by links 334.
The stent 400 has the same features as stent 300 described previously with the following exceptions. Rings 412a and 412b are sinusoidal and abut adjacent rings by W-crowns 414 and Y-crowns 416 (as is the case with rings 312a and 312e), however, as previously described, when crimping a stent to the minimum theoretical crimp diameter (D-min), the loop structure of rings 412a and 412b near marker 20 is modified to avoid overlapping with the struts.
Referring to fig. 4A and 4C, close-up views of stent 400 at section IVA and section IVB of fig. 4, respectively, are shown. To avoid the overlap discussed above, the spacing between the strut portions of the w-crowns at the markers is increased for rings 412a and 412 b. This improvement is illustrated by the w-crown 414. The elongated crown (along axis B-B) provides more space between the strut 430 and the marker structures 21a, 21B to avoid overlap (the curled shape produced with this modification is shown in figure 4D). W-crown 414 improves scaffold structure in the vicinity of marker 20 in at least one of ways (1), (2), and (3) as compared to w-crown 309, which is not associated with marker link 20:
(1) the crown flat or non-curved surface portion B1 is increased in direction B-B over the other w-crown 309 flat surface portion B2, for example, by about 350% to 400% for a maximum width (ts) of the marker link that is about 200% greater than the non-marker link width (tL).
(2) The distance from w-crown 414 (peak) to adjacent u-crown 407 (valley) is increased compared to the distance from y-crown 316 (peak) to adjacent u-crown 307 (valley) of ring 312b, and/or for any ring 312 the distance from w-crown 309 (peak) or y-crown 310 (peak) to adjacent u-crown 307 (valley). This is illustrated in the figure by comparing distance X412 and distance X312, measuring the length from the peak center to the valley center of ring 412 and ring 312, respectively. The distance X412 may be about 15% greater than X312 for a marker link maximum width (ts) that is about 200% greater than a non-marker link width (tL).
(3) The distance from peak 414 to adjacent peak 407 is greater than the distance from peak 407 to peak 409 or L1 is longer than L2 in fig. 4A, e.g., L1 is about 10% longer than L2, and/or L1 is about 5% longer than the distance between any adjacent peaks for rings 312a, 312b, 312d, and 312f and the maximum width (ts) of the marker link that is about 200% greater than the non-marker link width (tL).
The features of ring 412a are equally applicable to ring 412b adjacent marker link 20. Fig. 4B shows a view of portion 302 with loop 412a shown in phantom above loop 312a of stent 300. Additional spacing between marker link 20 and strut 430 is indicated by "increased spacing" in the figure. The difference in half-cycle length of the sinusoidal ring segments (X412, X312) extending between the marker link y-crown and w-crown, respectively, can also be seen in this figure. In addition, the ring 412a is characterized as symmetrical about the w-crown 414. Thus, the improvements of at least one of (1), (2), and (3) discussed above apply to both sides of the w-crown 414.
According to another aspect of the stent 400, the "added space" noted in connection with the stent 400 avoiding MBOL or overlap, is also a factor in facilitating deformation of the structures 21a, 21b when swaging marker elements, rivets or beads into holes for embodiments that make the stent marker links and connecting rings avoid overlap, for some embodiments that avoid overlapping of the stent marker links and connecting rings.
Fig. 4D shows a portion of stent 400 in a crimped state, where the stent is crimped to D-min. As can be seen, the additional spacing between the strut portions 430a, 430b of the w-crowns 414 at the marker link 20 results in no overlap or no negative overlap when the stent is crimped to the theoretical minimum crimp diameter D-min. Specifically, FIG. 4 shows that with the improvement to a ring 412 having W-crowns 414 connected to marker links 20, when the stent is crimped to D-min, the struts and/or U crowns adjacent to and above and below the marker structure are spaced apart by a distance greater than or equal to the maximum width (ts) of the marker structure. When the scaffold with loops 412 is crimped to D-min, there is no overlap. When the stent is crimped to about D-min, the marker link is everywhere located between the crown and the strut.
It has been found that when tracking a thin-walled stent similar to stent 300 by simulating calcification and distortion of the anatomical model, distal annulus deformation is observed as the struts ascend along their path and touch obstacles. Furthermore, the marker structure 21 and the hole 22 may be deformed/stretched leading to potential displacement of the marker material. To address the concern of separation of the marker material from the thin-walled stent, the marker links are made more flexible in bending by lengthening the links and/or reducing the width of the portion of the link connecting the structure 21 with the adjacent Y-crown or w-crown. This change results in a more flexible hinge region adjacent the marker structure 21, thereby positioning the deformation to a point away from the structure 21 to prevent the marker hole 22 from being affected by significant deformation. This variation also makes the distal and/or proximal portions of the stent more flexible and conformable to the balloon, thereby reducing the likelihood of the strut rising or snagging during delivery to the target site.
Fig. 5 shows a close-up view of another embodiment of a stand or stand 500. The view of fig. 5 is the same as section IVC of fig. 4 and stent 500 has all the features of stent 400 except that the marker links that abut rings 412a and 312a and rings 412b and 312f are changed. Marker link 520 differs from marker link 20 in that an additional link 520b is added or the existing link to the right of marker structure 21b (see marker link 20) is lengthened. The addition or lengthening of the marker link portion results in an increase in distance a12 compared to when marker 20 is used. Additionally, distance A12 is longer than distance A23 that separates rings that are not adjoined by a marker link (e.g., rings 312b and 312c in FIG. 5). The same change is made to the marker link extending between rings 412b and 312 f-marker link 520 replaces marker link 20-. Marker link 520 may also replace marker link 20 in stent 300 (at the proximal and distal ends). In this case, the same features discussed in relation to the bracket 400 with the link 520 also apply to the bracket 300 with the link 520.
It has been found that when the linkage 20 is replaced by the marker linkage 520, there is less tendency for the radiopaque material held by the marker structure 21 to dislodge or separate from the stent when the stent is crimped, balloon expanded, or tracked through a tortuous vessel. The reason for improved retention can be understood by considering the strain energy distribution on the tie rods as the stent deforms or the y-crowns 316 of ring 312b move relative to the w-crowns of ring 412 a.
Marker link 20 is deformed if crown 316 of ring 312B is moved radially outward or inward relative to crown 414 of ring 412a, or if the crowns are moved in opposite directions along axis B-B. A significant portion of the strain energy in the linkage 20 caused by such deformation is carried in the marker structures 21a, 21b because the linkage portions to the left and right of the structure 21 are relatively short and thick (and therefore, there is little deformation in this portion of the marker linkage and therefore less strain energy is experienced there). Because when the ring movement is made (i.e., the rings will move relative to each other by a prescribed amount regardless of the stiffness of the links, because the ring movement is caused by a forced displacement or overwhelming force, such as by crimping jaws closing on a stent), the load must act somewhere along the marker links, with strain energy being carried primarily in the marker structure 21, which is more easily deformed than the short and thick link portions near the crown. This deformation may alter the shape of the hole in which the marker material is located, resulting in a loss of retention. By lengthening the rod portion of marker 20 or adding rod 520b that is significantly longer than rod 520a, which characterizes the length of the rod portion to the left and right of structure 21 of rod 20, less strain energy is carried in structure 21 and more in rod 520b on the contrary. Thus, there is less tendency for the marker material to shift during crimping or bending of the stent, as the marker holes 22 retain their shape under these loading conditions. In other words, deformation of the links occurs primarily in the elongated portions 520b so that the apertures 22 retain their shape. In addition, link 520b also increases the flexibility of the link, thereby enabling easier movement of ring 312b or 312f relative to ring 412a and ring 412b, respectively. This aspect is advantageous to avoid the problem of the distal annulus expanding or protruding from the balloon when the catheter is advanced around in tight vasculature (object (iv) above). It is also noted that the marker 720 discussed in connection with fig. 7 addresses targets (iv) and (iii) similarly.
According to one example, the link 520b forming the y-crown 316 has a width (tm2) that is about 60% less than the width (tm1) of the link portion 520a that connects to the ring 412a and forms the W crown 414. Further, length A12 is approximately 27% longer than length A23 to accommodate link 520 with the newly added link portion 520 b.
When tracking a thin-walled stent crimped to a delivery system by simulating calcifications and curved anatomical models, distal end loop deformation is observed as the struts touch obstacles along their path. To understand the possible causes of strut touch, the thin-walled stent was crimped to the same configured delivery system and placed in a bend similar to that found in the anatomical model observed under a microscope. It can be observed that the balloon is compressed at the inner bend of the curve and tensioned at the outer bend of the curve. When tightened, the balloon stretches and conforms to the curve. If the w-crown associated with the marker link happens to be positioned at an outer bend of the bend, the w-crown will straighten out (see fig. 6B) rather than conform to the potentially curved balloon material at the distal end 15 a. The w-crown portion of the stent remains straight because it is rigid due to the marker material and structure 21.
Fig. 6 shows a partial plan view of an end portion of a stent or stent 600 according to another embodiment. Left side or distal portion 602 (i.e., the left side of fig. 6) includes sinusoidal rings 312a, 412a, and 312c, where ring 312a is the outermost ring. Right or proximal portion 604 (i.e., the right side of fig. 6) includes sinusoidal rings 312d, 412b, and 312f, where ring 312f is the outermost ring. As can be appreciated from fig. 6, the distal portion 602 is different from the proximal portion 604. The modification to stent 300 or stent 400 is to account for the presence of an indeterminate distal, outermost loop when a stent mounted on a balloon catheter is advanced around a sharp turn in a blood vessel.
The proximal portion 604 of the holder 600 is identical to the proximal portion 304 or 404 associated with the holders 300 and 400, respectively. The distal portion 602 is altered from the distal portion 302 or 402 in the following manner.
The (distal) marker link 20 of the stent 600 is located between the inner distal rings 412a and 312c as opposed to the (proximal) marker link 20 being located between the outermost distal ring 312f and the inner ring 412 b. Such a change to the distal end 602 is desirable for at least one of reasons (a) and (b):
(a)improved conformance to distal balloons: marker link 20 is stiffer than link 634 or for that matter link 334 when bent, which can result in the distal outermost ring separating from the balloon distal end. When it is not desired to change the marker link structure, or it is not feasible (e.g., because the structure requires radiopaque material that provides sufficient surface area to maintain the desired volume), a significant reduction in bending stiffness of the link connecting the outermost ring 312a with the inner ring 412a can be achieved by moving the marker link 20 between the inner rings. This ability then dramatically reduces the bending stiffness between the outermost two rings 312 a-goal (IV) -is achieved.
(b)Minor strain in marker-retaining structures: when the stent is traveling around a sharp turn, the outermost rings will experience the greatest strain as the stent is bent. For embodiments of the stent where it is undesirable to have less stiffness when bending the outermost ring relative to the adjacent inner ring (e.g., whereFor purposes of drug coverage or vessel support, it is important to avoid a decrease in the radial stiffness of the outermost ring or to avoid increased spacing between rings, both of which can occur when the connecting links are made longer to become more flexible), by moving the marker links 20 to a position between the inner rings, the bending strain of the links 20 that can displace the marker material is avoided or mitigated. That is, because the bending strain in the stent (which occurs when a sharp turn is formed by the catheter) is higher between the outermost ring and the adjacent inner ring than between the inner rings, by having the links 20 between the inner rings (without having to change the marker link structure), the bending strain on the marker structure 21 becomes smaller. The objects (II) and (III) are achieved.
The bracket 600 is distinguished from the brackets 300 and 400 by the type of link used to connect the outermost and inner rings, i.e., the link 634 connecting the ring 312a and the ring 412 a. By three non-linear link struts 634 abutting the outermost distal ring 312a and the ring 412a, the non-linear link struts 634 are significantly more flexible in bending than the link struts 334 which are connecting the inner rings. This also helps explain the use of the stent 600 pattern for the distal end.
The nonlinear link struts may have various shapes, but have some specific limitations, such as providing sufficient spacing for crimping, such as a D-min crimp profile. This type of link shown in fig. 6 has a U-shaped middle portion 636, with the middle portion 636 connected to respective y-crowns and w-crowns by short, straight link portions and long, straight link portions, respectively. The link portion joining portion 636 and the w-crown is longer than link portion 632a joining the y-crown to provide sufficient clearance for the ring stay during crimping (as explained below). With this provided clearance, the w-crown 309 formed by link portion 623a can be crimped to D-min without the U-shaped portion 636 interfering with strut 330 or without strut 330 overlapping U-shaped portion 636 in the crimped state.
Referring to fig. 6A, a crimped side profile of a stent 600 is shown. The illustrated link 634 includes a long straight link portion 632a and a short straight link portion 632b with a U-shaped middle portion 636. Length a12 (measured relative to axis a-a) may exceed length a23 by approximately the length of U-shaped portion 636, or the sum of the lengths of portions 632a and 632b may be approximately equal to a23, less than the strut width of the ring. In one embodiment, length a12 is about 40% greater than length a 23.
In other embodiments, the U-shaped portion 636 can be replaced by a link with a smaller moment of inertia for the area between portions 632a and 632b, an S-shaped cutout portion or a narrowed portion in place of the U-shaped portion. Examples of these link types are described in US 20140039604 at fig. 14B, 14C, 14D, 14E and 14F and the accompanying paragraphs [0223] - [0229 ]. By "non-linear" link strut is meant any of these links.
Fig. 6B is an image showing a deformed distal end portion of a medical device including a balloon catheter having a shaft 2 and a stent crimped to a balloon 15. As can be seen in this figure, when the catheter is guided around a sharp turn (as traced over a guide wire), the balloon distal end and shaft coincide with the angle of the turn, but the stent distal end 7 does not coincide. More specifically, the outermost ring 5 flares or protrudes outwardly from the distal end. The protruding structures 5 can hit the walls of the vascular system. The most immediate problem with this orientation of the stent relative to the distal end of the balloon is damage that may be caused by the loops 5 hitting the vasculature and damaging the stent (due to excessive bending strain). The damage that may occur is mentioned above. First, the marker linkage structure may deform and cause displacement of the marker material. Second, the strain may result in cracking of the ring 5, or crack propagation within the ring 5.
One solution to this problem may be to make the end rings stiffer when bent, so that the vessel occlusion gives way to make room for the expanded or protruding stent ends. For example, the end rings may be made thicker or the number of connecting links between the outermost and inner rings may be increased. However, it is preferable to make the loop stiffer so that the stent end is more consistent with the balloon distal end. It is also preferable to limit the load applied to the marker link for the reasons previously described.
Fig. 6C is an image of the stent distal end 602 mounted at the distal end 15a of the balloon 15 when the catheter makes a similar sharp turn in the vasculature. It can be seen that by reducing the bending stiffness of the ring 312a relative to the inner ring (ring 312b), the end ring 312a conforms to the shape of the balloon distal end 15 a. In the case of the stent 5, the end rings 312a do not expand or protrude as in the case of the stent 5. The link 632 acts as a hinge to accommodate compression and tension, which when the crimped stent is placed on a bend, the bend will be applied to the distal ring causing compression and tension.
Conformance of the distal stent to the distal end of the balloon can also be achieved by changing the marker linkage structure to become more flexible when bent. Indeed, a w-crown formed from a marker link in accordance with the discussion herein may substantially reduce stiffness at the w-crown associated with marker link 314. The thin-walled stent design allows the marker link to be attached to the outermost ring without the straightening problems discussed above.
Fig. 7 shows an end portion partial plan view of a stent or stent 700 according to another embodiment. The left or distal portion 702 (i.e., the left side of fig. 7) includes sinusoidal rings 312a, 312b, and 312c, with ring 312a being the outermost ring. The right or proximal end portion 704 (i.e., the right side of fig. 7) includes sinusoidal rings 312d, 412b, and 312f, with ring 312f being the outermost ring. As can be appreciated from fig. 7, the distal portion is different from the proximal portion. Such modifications to stent 300 or stent 400 are also made to address the uncertain occurrence of distal-most end loops when a balloon catheter-mounted stent travels near a sharp turn in the vasculature.
Proximal portion 704 of stent 700 is the same as proximal portion 304 or 404 associated with stents 300 and 400, respectively. Further, the distal portion 702 has the stent 600 in features at the distal portion 602 other than some of the following features.
The marker 720 (fig. 2B) is located between the outermost ring 312a and the inner ring 312B, as opposed to the marker link 20 or 520 being located between the inner rings in the case of the stent 600. The marker link of the stent 700 is also different from the marker links of the previous embodiments. As in the case of marker 20 or link 520, marker link 720 has a marker structure that is oriented vertically rather than horizontally. That is, the marker structure 21a is offset from the marker structure 21B along the axis B-B rather than the axis A-A. With a long, straight link portion 732a connecting structure 21 at one end and forming a w-crown 314 and a shorter link 732b forming a y-crown 316 at the opposite end.
The outermost ring 312a of the stent distal portion 702 is connected to the inner ring 312b by one marker link 720 and two of the non-linear links 634 used in the stent 600. Adjacent inner rings are not connected by marker link 720 or link 634. A link 334 is used. In contrast to marker link 20, marker link 720 is more flexible in bending due to the length of portion 732a and is advantageously located between the outermost ring and the adjacent inner ring to more easily position the end of the stent under fluoroscopy. Additionally, when the marker 720 is used, one or more of the following advantages may also be present. First, the marker is more flexible so that the outermost ring will more readily conform to the balloon as the catheter travels around sharp turns in the vasculature. In this sense, the marker 720 has some of the same advantages as the marker 520 (targets (ii) and (iii)). And without the need to alter the ring structure to be able to crimp a ring having a w-crown formed by the marker link. The loop 312a may be crimped to D-min because the structure 21 does not interfere with the loop structure 21 (object (i)).
Fig. 6A and 7A illustrate the coiled state of stent 700 and the length between rings a12, a23 near marker 720 and link 634. It will be appreciated from these views that the portions 732a and 632a of the marker and linkage, respectively, have lengths that allow the outer ring 312a to be crimped to D-min without interference from the U-shaped portion 636 or the marker structure 21. It can be seen from these views that the structure 21 with the holes 22 and the U-shaped structures 636 is located between the U-crown near the left side of the W-crown of the ring and the U-crown near the right side of the Y-crown of the ring.
Referring to fig. 7B, a close-up view of section VII from fig. 7 is shown. As shown here, portions 732a and 732b have lengths c1 and c2, respectively. Portions 632a and 632b are also c1 and c2 in length. Lengths a12 and a13 for stent 700 are also shown (a12, a13, c1 and c2 also apply to the lengths of portions 632a and 632b and the loop spacing of stent 600). The sum of lengths c1 and c2 is equal to a12 and is less than the length of the U-shaped portion 636 and the width of the crown. In some embodiments, a12 is about 40% greater than a23 and c1 is about 36% greater than c 2. When the stent is in a crimped state, length c1 is approximately equal to the distance between the valley of an adjacent crown and the w-crown formed by portion 732a or 632a, less the width of crown 314 or strut 330 (see fig. 6A-7A). The marker structure is located on the right side of the U-crown adjacent to the W-crown formed by the marker link.
Fig. 7C is an image of the distal end 702 of the stent mounted on the distal end 15a of the balloon 15 when the catheter makes a similar sharp turn in the vasculature. It can be seen that the end loops 312a conform to the shape of the balloon distal end 15a by reducing the bending stiffness of the loops 312a relative to the inner loop (loops 312 b). The end annulus 312a is not expanded or protruded as in the case of the stent 5.
Table 2 shows the dimensions associated with an embodiment of the manufactured stent corresponding to the embodiment of the stent shown in the drawings (which means the same value as the immediately left cell when the input is "-". accordingly, the value of tm2 for stent 400 is 217, and the lengths B1 of stent 500 and stent 700 are 374 and 78, respectively).
Figure GDA0002576218240000241
Figure GDA0002576218240000251
Referring to table 2, this table 2 can be understood from the above examples and was discussed previously in connection with scaffold 300 as compared to scaffolds 400, 500, 600 and 700; facing the needs associated with crimping and/or delivering stents through tortuous arteries, there are variations in wavelength, 1/2 wavelength, marker link width, length and orientation, non-marker link type and length, ring spacing, and crown width at the marker links, respectively. These relationships apply to thin-walled stents, whether in the crimped state or prior to crimping. Thus, the above relationship also applies when referring to a crimped stent. It should also be understood that features of the racks 400 and/or 500 other than the rack 300 may be incorporated into the racks 600 and 700. Or features of the stand 400/500 may not be included in the pattern of the stands 600 and 700.
The following discussion relates to the primary satisfaction of goal (ii): radiopaque material is secured within the stent openings provided by the marker structures 21a, 21 b. As previously mentioned, it has been found that with thin-walled stents, the marker material cannot be reliably retained in the marker hole by frictional engagement with the cylindrical hole wall. To meet goal (ii) in a preferred embodiment, the radiopaque material is secured to any of the stents 300, 400, 500, 600 or 700 by riveting a rivet-like body of the marker material to the marker structure 20, 520 or 720, while not obstructing any of the other goals (i), (ii) or (iv). In some embodiments, the attachment and fixation of the marker does not include any additional polymer, adhesive, or reshaping of the cylindrical bore (other than the deformation that occurs during the swaging process). In a preferred embodiment, the drug-polymer coating is applied after the marker is placed in the hole.
A marker shaped as a rivet is used instead of a spherical marker for the cylindrical hole. Fig. 8A and 8B show side and top views, respectively, of a tag 27 shaped as a rivet. The head 28 may include a distal cavity surface 27a and an inner cavity surface 27b of the rivet 27. In the figure, the head 28 includes a distal cavity surface 27 a. It may be preferred that the head 28 is a distal luminal surface portion of the rivet 27 for assembly purposes, as the stent may then be placed on the mandrel and the tail of the rivet may be deformed by a tool (e.g., a pin) applied externally to the distal luminal surface of the stent. Rivet 27 has a head diameter d1 and shank 27c diameter d2 is approximately equal to the hole 22 diameter. The head portion 28 has a height h2, and the height h2 is approximately the amount by which the head portion 28 will extend beyond the distal luminal surface 22a of the strut portion 21 a. Although not desired, it is acceptable for the head 28a to protrude no more than about 25 microns, or from 5 to 10 microns up to 25 microns, from the distal luminal surface 22a, or the head to extend no more than 25% of the strut thickness. An equal amount of protrusion beyond the interior cavity surface 22b is accepted for the deformed tail of the rivet.
Referring to fig. 9, a rivet in hole 22 is shown. The deformed tail 27 b' secures the rivet 27 in the hole 22. The overall height h1 is preferably no more than about 40% or about 10% to 40% greater than the strut thickness (t) and the tail height is approximately equal in size or within 5-20 microns compared to the head height h 2.
The rivet 27 can be attached to the hole 22 by first inserting the rivet 27 into the hole 22 from the hole side of the bracket so that the head 28 rests on the inner cavity surface 22b of the strut portion 21 a. The stent is then slid over the tightly fitting mandrel. With the mandrel surface pressed against the head 28, a tool (e.g., a pin) is used to deform the tail 27b to form the deformed tail 27 b' in fig. 9. In some embodiments, the rivet may first be inserted into the bore 22 from the distal side so that the head 28 rests on the distal surface 22a of the strut portion 21 a. With the head 28 held in place by a tool or flat surface applied to the distal luminal surface, the tail 27b is deformed by a tool, pin, or mandrel inserted into the hole or through the stent pattern from an adjacent location on the distal luminal surface. In some embodiments, the rivet 27 may be solid (fig. 8A-8B) or hollow, for example, with the shank being a hollow tube and the opening extending through the head 28 of the rivet.
In some embodiments, the rivet is a hollow or solid cylindrical tube and lacks a preformed head 28. In these embodiments, a tube (solid or hollow) is first fitted into the hole, and then a pressing tool is used to form the head and tail portions of the rivet. According to preferred embodiments, there is a process of making radiopaque markers as rivets, mounting rivets on stents, and stents having these markers mounted thereon. First, a process for making a rivet-shaped marker from beads is described.
As described above, the head and tail portions of the marker help the marker to remain in place, for example, when an external force is applied to the rivet or linkage deforms during crimping or balloon expansion, or the stent makes a sharp turn in the vessel. However, in some embodiments, there is no tail portion (e.g., tail 27b 'of rivet 27' in fig. 9). Instead, the shank of the rivet is deformed into a trapezoidal or frustoconical shape or has an enlarged end (e.g., rivet 137' shown in fig. 15A). It has been found that this type of marker creates increased resistance to being pushed out of the bore of the strut or link when the stent is subjected to an external force that deforms the link or strut holding the marker.
It is desirable to select a bead of appropriate size for forming the rivet. According to some embodiments, the bead size or bead volume used depends on the strut thickness (t), the hole diameter (D2), the distance between holes D1, and the edge thickness (D2) of the stent structure (e.g., a tie rod strut with holes in fig. 2A or fig. 2B) to which the rivet is attached. The starting material may be spherical or cylindrical. Raw materials made of radiopaque materials are available from commercially available sources.
According to the present disclosure, the rivet marker is manufactured using a raw bead to fit in the bracket hole 22. In a preferred embodiment, the rivet markers are mounted or joined to stent holes of thin-walled struts or struts that have a thickness (t) preferably less than about 100 microns. The process of making the rivets and the step of attaching to the bracket can be summarized as a six-step process.
Step 1: marker beads are selected from the starting material having a diameter or volume within the desired range, i.e., a diameter or volume suitable for mounting on a stent according to the dimensions D0, D1, D2 and t (fig. 2B). Selection of marker beads having a desired diameter or volume, or removal of too small beads from a batch, can be accomplished using a mesh screen. The batch of beads was screened on a mesh screen. Beads that do not have the smallest diameter or volume will fall through the openings in the mesh screen. Alternative methods known in the art may also be used to remove unwanted beads or to select beads of a suitable size.
Step 2: the beads selected from step 1 are deposited on a stamp plate.
And step 3: the rivet is cold formed by pressing the bead into the die plate. At a temperature near ambient temperature, the bead is forced through a die (e.g., using a plate, mandrel head, pin, or conical ram head) to thereby reform the bead into a rivet defined by the die shape and the volume of the bead relative to the volume of the die receiving the bead.
And 4, step 4: the formed rivet is removed from the die plate. The formed rivets have an overall length of about 190-195 microns and a diameter of about 300-305 microns and are removed using a tool having a vacuum tube. The air pressure is adjusted to cause the rivet to grip at or release from the tip. This is done by placing the opening of the vacuum tube over the rivet head, reducing the air pressure within the tube so that the head adheres to or sucks in the tube tip (due to the difference in air pressure), and lifting the rivet from the die.
And 5: while the rivet remains attached to the tube tip, it is moved to a position above the stent hole, the rivet is placed in the hole using the same tool, and the air pressure within the tube is then increased to ambient air pressure. The rivet is released from the tool.
Step 6: the rivet and/or hole are deformed to enhance the resistance of the joint or marker to dislodgement from the hole, e.g., fig. 14A-14C.
It will be appreciated that the problem of handling non-spherical beads is solved according to steps 1-6. For example, steps 1-6 above, where the rivet does not need to be reoriented after it is formed from spherical beads, overcome the problem of orienting the spherical beads so that they can be aligned and placed into the hole.
Referring to fig. 16A, 16B and 16C, the steps associated with transferring the shaped rivet 127 '(or 137') from the die 200 (or 205) to the stent strut hole 22 using the vacuum tool 350 are shown. It will be appreciated that the radiopaque marker 127 'is formed to be extremely small (i.e., less than 1mm in its largest dimension), such that the marker 127' is complicated to handle and orient for placement into the hole 22 (as opposed to placing a ball into the hole) due to the need to orient the stem relative to the hole. For this reason, the swaging or forging process is combined with placement into the stent bore by removing rivet 127 ' from bore 200 with tool 250 (FIG. 16A), holding rivet 127 ' attached to the tool while maintaining the orientation (FIGS. 16B-16C), and then placing rivet 127 ' in bore 11a (FIG. 16C).
Referring to fig. 10 and 11A, a first embodiment of a die 200 according to the present disclosure and a marker 127 formed using the die 200 are shown, respectively. The die is a flat plate having a top surface 201 and a through hole extending from the upper end 201 to the lower end. The bore has an upper end diameter dp2 and a smaller lower end diameter dp1 that is less than dp 2. The aperture 202 is preferably circular throughout, although in other embodiments the aperture may be rectangular or hexagonal in thickness tp, in which case dp1 and dp2 are across the length or extent (as opposed to diameter) of the aperture. And the plate 200 has a height tp. The taper angle is related to dp2 and dp1 by the expression tan Φ ═ (1/2(dp2-dp1)/tp), and in preferred embodiments Φ is 1 to 5 degrees, 5-10 degrees, 3-5, or 2-4 degrees. The shape of the die 200 produces a frustoconical shank as shown in fig. 18A. A raw material bead (not shown) is placed at the upper end of the opening 202 such that the bead is partially within the well 202. A plate, mandrel or pin ("ram head") is then pressed into the top of the bead to force the bead into the aperture 202. The beads are forced into the holes until the ram head is approximately a distance HH from the surface 201. The rivet 127 formed by the foregoing molding process has a taper angle Φ over all or most of the shank height SH, and the shank shape is a truncated cone. The overall height of the rivet is HR, the head thickness is HH and the head diameter is HD. In some embodiments, angle Φ is small enough that the shank can be considered a cylinder, or Φ is about 0.
Referring to fig. 12 and 13A, a second embodiment of a die 205 according to the present disclosure and a marker 137 formed using the die 205 are shown, respectively. The die is a flat plate having a top surface 206 and a hole extending from an upper end 301 to a lower end. The hole has a constant diameter dcb1 throughout. A counterbore is formed in the upper end 206. The counterbore has a diameter dcb 2. The aperture 207 is preferably circular throughout, although in other embodiments the aperture 207 may be rectangular or hexagonal in thickness tp, in which case the dcb1 is across the length or extent (as opposed to the diameter) of the aperture. The shape of the die 200 is formed with a rivet having a stepped cylindrical shape or a cylindrical shank with a head, as shown in fig. 13A. A raw material bead (not shown) is placed at the upper end of the opening 207 such that the bead is partially within the aperture 207. The ram head is then pressed into the top of the bead to force the bead into the aperture 207. Forcing the beads into the bore until the ram head is approximately a distance HH from the surface 206. The rivet 137 formed from the previous forming process has the shape shown in fig. 13A. The overall height of the rivet is SH + HH, the head thickness is HH, the shank height is SH and the head diameter is HD.
Tables 3 and 4 below provide examples of rivet sizes for rivets used to be secured in the connecting rod bores 22, for example as shown in fig. 2A. In this example, the thickness of the tie rod is 100 microns and the micron values of D0, D1, and D2 are 241, 64, and 64, respectively.
The dimensions tp, dp2 and dp1 of die 200 have values of 178, 229 and 183, respectively. The dimensions of the formed rivets obtained using the die 200 are shown in table 3. From the results, it can be seen that the shank length (or height) is 150% or more of the tie rod thickness and the rivet Head Diameter (HD) is significantly larger than the hole 22 diameter. HD. The mean and standard deviation of SD and SL were based on the respective "n" samples of the measured rivets.
Figure GDA0002576218240000281
Die 300 dimensions dcb2 and dcb1 have values of 305 and 203. The dimensions of the formed rivets obtained using the die 300 are shown in table 3. HD. The mean and standard deviation of SD, HH, and SL were based on the respective "n" samples of the measured rivets.
Figure GDA0002576218240000282
Figure GDA0002576218240000291
In tables 3 and 4, "after swaged o.d. rivet head diameter" refers to the outer diameter of the rivet marker after it is pressed into the bracket hole.
An example of a process for installing the rivets 127, 137 into the bracket holes 22 will now be discussed. According to some embodiments, a rivet marker is placed into the hole 22 from the distal lumen or outside of the stent so that the head is located on the distal lumen surface 22 a. Rivets may alternatively be placed from the lumen side of the hole. The rivet is pressed firmly into the hole so that the largest portion of the shank extends from the inner or distal cavity side, respectively.
With regard to the rivet 127, after it is placed in the hole 22, the side opposite the head is subjected to a swaging process. Referring to FIG. 11B, deformed rivet 127' is shown in cross-section in hole 22. Rivet 127 ' has a head 127a ', which head 127a ' extends from surface 22a by an amount h 2. The length h2 may be about 25 microns, 25-50 microns, or 5-50 microns. The same dimensions apply to the tail portion 127 b' extending from the opposite surface of the linkage rod (e.g., the inner cavity surface). The diameter of the head 127a ' may be greater than the diameter of the tail, or the diameter of the tail 127b ' may be greater than the diameter of the head 127a '. For example, rivet 127 is placed into from surface 22a (distal side) such that a majority of the shank length (e.g., 50% of the post strut) extends from the lumen side. A cylindrical mandrel (not shown) is placed through the bore of the holder. The mandrel has an outer diameter slightly less than the inner diameter of the stent and provides a swaged surface to form the tail 127 b'. The spindle rolls back and forth over the shank portion extending from the inner cavity surface. This movement causes the shank material to flatten out around the hole, forming tail portion 127 b'. The resulting rivet 127 ' is at least partially fixed in place by the tail portion 127b ' resisting the force of pushing the rivet toward the distal cavity side of the hole and the head portion 127a ' resisting the force of pushing the rivet toward the inner cavity side of the hole 22. As shown, the deformation of the shank forms a tail 127 b' having a flange disposed on the surface 22 b. The flange may be circular like a head and may have a flange radial length that is greater or less than the radial length of the flange of the head 127 a'.
Referring to fig. 15A and 15B, a stepped mandrel is used in conjunction with a ram head to create a rivet 137' from the rivet 137. The rivet has a shank 137', which is reshaped from, for example, a generally cylindrical shape to the shape shown in fig. 15A-15C when the die 205 is used. Such a shank shape is characterized by a taper angle θ of about 5-15 °, 5-9 °, or about 3-8 °. The shank of the rivet in hole 22, according to some embodiments, is frustoconical, with the opposite or distal shank end of head 137a ', or end 137b ', being larger or of greater diameter than the shank portion that is closer to or closest to head 137a '. The deformed shank 22 'may have a shank diameter S2 at one of the distal and inner cavity side openings closest to the bore 22', the shank diameter S2 being greater than the shank diameter S1 at the other of the inner and distal cavity side openings, or S2 > S1. According to some embodiments, as shown in fig. 15A, the cylindrical bore 22 may also be deformed into a bore 22', the bore 22' having a larger opening at the surface 22b than the bore opening at the surface 22 a. According to some embodiments, both the hole 22 and the rivet 137 are deformed when the rivet 137 is installed on the bracket.
The structure shown in fig. 15A may be made by a second process of attaching a rivet marker to the bracket hole 22. In contrast to the first process, the tool does not roll on the surface of the shank where the tail portion protrudes from the aperture opening. Instead, the tail end of the shank is pushed directly into a non-compliant surface, which may be the surface of a metal mandrel. The rivet is forced to deform by the compressive force between the mandrel surface and the head of ram 234, pushing the rivet into the mandrel surface. In contrast, the first process of creating deformed rivet 127' is formed by a combination of constraints rolling a hard surface into the shank and head 127a, which holds the rivet head against surface 22a while swaging tail end 127 b. Under the second process, the line of action of the force is either entirely along the axis of the rivet, or perpendicular to the rivet head. The result is a flat or widened shank portion and deformed hole with little or no flange or edge formed from the tail portion of the shank.
The second process is now described in further detail with reference to fig. 14A-14C. The stent 400 is placed on the stepped mandrel 230. The mandrel has a first outer diameter and a second outer diameter that is less than the first outer diameter. The stent portion holding the marker 137 is placed on the smaller diameter portion of the mandrel. The larger diameter portion of the mandrel 230 holds the adjacent portions of the stent. The smaller diameter portion of mandrel 230 has a surface 230a and the larger diameter portion has a surface 230 b. As shown in fig. 14B, 14C, ram 234 pushes the stent holding marker 137 into mandrel surface 230a with force F, which causes the stent end to deflect a distance "d" toward surface 230a (fig. 14A). After the stent reaches surface 230a, ram 234 continues to push (by pressing directly against head 137a) into the portion of the stent holding the marker to form deformed marker 137 'and hole 22' as shown in fig. 15A. The selected surface 230a may be smooth or free of grooves, dimples, depressions, or other surface irregularities (other than a cylindrical surface) that inhibit the flow of material during swaging. In a preferred embodiment, the mandrel surface is smooth as compared to the surface of the head 234 of the pressed-in rivet marker 137. That is, the coefficient of friction (Mu) between head 234 and surface 137a 'is greater than Mu between surface 230a and surface 137 b' of mandrel 230.
The deformed shank 137 'and aperture 22' shape shown in fig. 15b produces a higher external pushing force than previously thought ("external pushing force" refers to the force required to displace the marker from the aperture). Indeed, it was unexpectedly found that the deformed rivet 137' and hole 22' have a higher resistance to displacement than a marker that fits into a connecting rod having a higher thickness of more than 50%, regardless of the presence of the head 137 '. For example, the test of the minimum displacement force required to push the rivet 137 'out of the side 22a of the hole 22' of a strut with a thickness of 100 microns is higher than the displacement force required to push out a marker installed according to US20070156230 (fig. 8A, 8B or where the sphere is deformed into a larger cylinder in a warehouse, increasing the surface-to-surface contact to a maximum) and a hole for a strut with a thickness of about 50% higher (158 microns and 100 microns). As shown in table 4:
Figure GDA0002576218240000301
even though stent a has more area of contact with the marker, stent B has higher external pushing force and thus higher friction against displacement. The results indicate that the deformation that occurs during the swaging process to form the deformed rivet markers and holes of FIG. 15A has a significant effect on the external pushing force (note: for stent B, the gram force external pushing force reported in Table 4 is applied to the lumen side 22B). Given the higher wall thickness of more than 50%, scaffold a should have higher displacement force (same bead material, bead volume and poly (L-lactide) scaffold material for scaffolds a and B). The shape of the deformed shank and hole may account for the higher displacement force, which essentially forms a lower portion 137 b' that is significantly larger than the opening 22a of the strut 22. Thus, the displacement force must be high enough to deform the opening 22a ' and/or the stem portion 137b ' in order to displace the marker from the 22a side of the hole 22' (as opposed to merely needing to substantially overcome the frictional forces between the material and the wall of the hole).
Shape 137' in FIG. 15B may be formed by a swaging process that deforms the rivet while it is within hole 22. The rivet may have the shape and/or characteristics of rivet 27, 127, or 137 prior to swaging. The lateral flow (shear flow) of the rivet material during swaging near tail portion 137b 'causes it to expand and yield (enlarge) the brace hole near opening 22 b'. This creates a trapezoidal or frustoconical shape of the rivet shank and hole. The swaging process of fig. 14A-14C applies equal and opposite forces that are generally collinear with the axis of symmetry of the rivet (as opposed to rolling motion on one side). If instead a cylinder or ball (as opposed to a rivet) is placed in the hole 22 and approximately the same coefficient of friction (COF) existing between the swaged surface 230a and the tail 137b is taken as the COF between the swaged surface 234 and the head 137a, but the same swaging process as in fig. 14A-14C, it is believed that a more symmetrical deformed marker results, depending on the COF being, for example, a flattened cylinder or barrel marker, such as the shape shown in US 20070156230. This result can be understood from Kajtoch, J Strain in the sizing Process, Metallurgy and Foundation Engineering, Vol.33,2007, No.1 (discussing the effect of the coefficient of friction between the ram and the ingot on the resulting shape with a slenderness ratio greater than 2). The shape of the radiopaque material forced into the hole is also a factor, such as the rivet 137 opposite the ball (stent a). The head presents a stem on one side that results in an asymmetrical shape about the strut midplane axis. It is believed that the combination of rivet shape and the difference in coefficient of friction produces advantageous results.
In a preferred embodiment, the smooth mandrel 230 surface 230a presses against surface 137b as compared to the rougher surface of head 234 pressing against surface 137 a. In a preferred embodiment, the coefficient of friction on the distal luminal side is greater than 0.17 or Mu > 0.17, while the coefficient of friction on the luminal side is less than 0.17 or Mu < 0.17. As noted above, the effect of the difference in coefficients of friction may be explained by the restriction of the shear or subsequent flow of material near the ends abutting the respective swage head. If the coefficient of friction is sufficiently low, then the surface area expands laterally, as opposed to being held relatively constant. Thus, since Mu is smaller on the luminal side, there is greater lateral flow than on the abluminal side. When combined with the use of a rivet shape, the result is believed to be a frustoconical shape as disclosed (e.g., as shown in fig. 15A-15B), which can be considered a shank having a locking angle θ.
After the marker is placed, there may be a heating step for the stent. In some embodiments, this heating step may correspond to a reactivation step of the scaffold polymer prior to crimping to eliminate the aging effect of the polymer.
Thermal recovery activity prior to the crimping process, including heat treatment of the bioabsorbable scaffold above its TG but below its melting point (Tm), can reverse or eliminate physical aging of the polymeric scaffold, which can reduce instances of crimp damage (e.g., at the peak of the scaffold) and/or label displacement.
According to some embodiments, the scaffold is heat treated, mechanically strained or solvent treated to cause the polymer to reactivate or to eliminate aging of the polymer shortly before crimping the scaffold onto the balloon and after placement of the marker. Restoring activity eliminates or reverses the change in physical properties caused by physical aging by restoring the polymer to a less aged state or even an unaged state. Physical aging causes the polymer to move toward thermodynamic equilibrium, while restoring activity moves the material away from thermodynamic equilibrium. Thus, restoring activity can alter the properties of the polymer in the opposite direction of those caused by physical aging. For example, restoring activity can reduce the density of the polymer (increasing the specific volume), increase the elongation at break of the polymer, decrease the modulus of the polymer, increase the enthalpy, or any combination thereof.
According to some embodiments, restoration of activity is required to reverse or eliminate the physical aging of the polymer that has previously occurred. However, restoring activity does not aim to remove, reverse or eliminate memory from previous processing steps. Thus, restoring activity also does not culture or impart memory to the stent or tube. Memory may refer to the transient polymer chain structure and transient polymer properties provided by previous processing steps. This includes a treatment step of radially strengthening the tube forming the stent by inducing biaxial orientation of the polymer chains in the tube as described herein.
With respect to marker-scaffold integrity or resistance to displacement during crimping, it has been found that the heating step can help reduce instances where crimping causes displacement of the marker. According to some embodiments, any of the foregoing embodiments of the marker retained in the scaffold hole 22 may include a heating step shortly before crimping (e.g., within 24 hours of crimping) after placing the marker in the hole. It has been found that the stent better retains the marker in the hole 22 after heating. After crimping and/or after expansion of the balloon from the crimped state, mechanical strain (e.g., limited radial expansion) or thermal recovery (raising the stent temperature to a short time above the glass transition temperature (Tg) of the load bearing portion of the stent polymer) can have a beneficial effect on the stent structural integrity.
In particular, these strain-inducing processes tend to beneficially affect the deformation of the voids 22 around the tag when the voids are deformed in the manner discussed in connection with fig. 15A-15B above.
According to some embodiments, the stent after the marker is placed is heated to about 20 degrees or 30 degrees above the glass transition temperature of the polymer in 10 to 20 minutes; more preferably, the stent load bearing structure (e.g., a portion made of a polymer tube or sheet material) is a polymer comprising poly (L-lactide) with the marker placed for 10 to 20 minutes and the temperature of the stent is increased to between about 80 to 85 degrees after placement of the marker.
According to some embodiments, it has been found that increasing the temperature of the scaffold after marker placement remodels portions of the cavity 22 to improve the fit of the marker in the cavity. Referring to FIG. 15C, after placing the rivet marker 137 into the hole 22 according to the second process, the hole shape deforms to create a lip or edge 140 at the end 137b ", which creates a higher resistance to displacement than for stent marker structures that have not been subsequently treated with a reactivation step. The surface 140a of the lip 140 interferes more with the displacement of the marker when the force is directed to the end 22 b'.
In light of the foregoing objective of obtaining a desired crimping profile of a thin-walled stent, there is a method for crimping such a stent to a balloon to meet the following needs:
structural integrity: when the stent is crimped to or expanded by the balloon, damage to the structural integrity of the stent is avoided.
Safe delivery to the implant site: the stent is prevented from being displaced or detached from the balloon during delivery to the implantation site.
Extended uniformity: uneven expansion of the stent ring is avoided, which may lead to structural failure and/or reduced fatigue life.
As previously reported in US20140096357, stents are not as elastic as highly ductile stents made of metal. Thus, these needs are particularly met for thin-walled stents that are more susceptible to rupture during crimping or balloon expansion.
Fig. 17A-17B illustrate steps associated with a crimping process for crimping a thin- walled stent 300, 400, 500, 600, or 700 according to the present disclosure to a balloon catheter (fig. 3D). It has been found that this crimping process can meet all of the above requirements for crimping a stent to D-min. In this example, a crimping process for crimping a 3.5mm scaffold to a 3.0mm semi-compliant PEBAX balloon is described. Fig. 17B graphically illustrates the crimped portion-stent diameter versus time plot of the flowchart of fig. 17A, wherein a balloon pressure of between about 20-70 psi (or 1atm above full or over-inflated balloon pressure) is applied substantially throughout the crimping process. For example, for steps a-G, the balloon pressure is maintained at 70 pounds, and then the balloon pressure is allowed to decrease (or deflate) to 50 pounds per square inch (or 1atm) during G-H. Balloon pressure was removed at point H. For steps H-J, there is no balloon pressure to obtain a low cross section or crimp to D-min and avoid damaging the balloon.
Fig. 17A shows three possibilities for curling according to requirements. First, two balloons are used: balloon a and balloon B. Balloon B was used for the pre-crimp step and balloon a (used with the delivery system) was used for the final crimp. Second, only one balloon (balloon a) was used for the entire crimping process including the verification alignment check. In this case, the stent inner diameter is larger than the fully or over-inflated balloon a. As such, during pre-crimping, displacement on the balloon is possible. Third, only one balloon (balloon a) was used for the entire crimping process without verification of the final alignment check. In this case, the balloon used in the delivery system has a fully or over-inflated state that is approximately equal to the inner diameter of the stent inner diameter.
Stage I: a scaffold supported on the fully inflated balloon of the balloon catheter is placed within the crimping head. When expanded and supporting the stent in this state, substantially all folds of the balloon are removed. In a preferred embodiment, the balloon of the catheter (i.e., the balloon used in the final product-stent delivery system) is used in stages I-II. In other embodiments, a second, larger balloon may be preferentially used for stages I and II (as explained in more detail below). The blades of the crimper are heated to raise the scaffold temperature to the crimping temperature. In a preferred embodiment, the crimp temperature is between the lower glass transition Temperature (TG) limit of the polymer and 15 degrees between TG.
After the scaffold reaches the crimping temperature, the iris of the crimper is closed to reduce the scaffold Inner Diameter (ID) to slightly less than the Outer Diameter (OD) of the fully or over-inflated balloon (e.g., from 3.45mm to about 3.05mm for a pebax3.0mm semi-compliant balloon inflated to about 3.2mm diameter). In this example, balloon B would be used for diameter reduction to a 3.0mm balloon size or balloon a size (e.g., a 3.0mm balloon).
Stage II: the crimper jaws were held at a 3.05mm diameter and this diameter was held at the crimping temperature for a second dwell time. After stage II, the stent had about 90% of its pre-crimped diameter.
The foregoing steps I-II reduce the stent diameter to the size of the fully inflated balloon of the stent delivery system (i.e., balloon a). Since the scaffold inner diameter is greater than the balloon full inflation diameter at the initial alignment check (prior to any crimping) (e.g., for balloons having diameters of 3.0mm to 3.2mm, respectively, the scaffold diameter is about 109% -116% of the full inflation balloon diameter), the scaffold may shift longitudinally (relative to the balloon) when crimped to balloon size. In view of this possibility, the scaffold is removed from the crimper and the alignment of the scaffold is checked on the balloon relative to the proximal and distal balloon markers.
Step "verify final alignment": when the stent needs to be adjusted on the balloon, the technician makes manual adjustments to move the stent into position. However, it has been found that these minor adjustments are difficult to make when the stent rests on the fully inflated balloon and has an inner diameter that is slightly less than the outer diameter of the balloon. To address this need, the balloon pressure is reduced slightly or the balloon is deflated temporarily to more easily accomplish realignment. When the scaffold is properly realigned between the balloon markers, the scaffold and fully inflated balloon are placed back into the crimper. With the stent inner diameter and balloon size now approximately equal, final crimping of the stent to the catheter balloon can begin. To ensure that the stent does not move any further longitudinally relative to the balloon, the stent diameter is preferably made slightly smaller than the fully inflated diameter of the balloon before phase III begins. As described above, where two balloons are used, balloon B is replaced with balloon a, alignment is performed with respect to balloon a and the scaffold is crimped to a final diameter on balloon B.
And stage III: the scaffold and balloon are returned to the crimper. The jaws close to a diameter about equal to or slightly larger than the diameter in phase II (to account for backlash that occurs during the alignment check). The crimper jaws are held at this diameter for a third dwell time, which may be the time required for the scaffold to return to the crimping temperature.
Then, if the balloon is not pressurized and has randomly distributed folds, the iris diameter is reduced to an ID corresponding to an OD about or slightly less than the balloon. That is, if the balloon is pressurized and then deflated such that all of the preformed folds are substantially replaced by random folds, the scaffold is crimped to approximately the OD. For example, for a 3.5mm stent, the iris diameter is reduced to about 1.78 mm. After the diameter reduction, the scaffold OD was about 60% of the scaffold diameter in stage III and about 50% of the starting or pre-crimp OD.
And stage IV: after reducing the scaffold OD to about 50% of the scaffold starting diameter, the crimper jaws were held at this crimped diameter for a third dwell time. In a preferred embodiment, the balloon pressure is slightly reduced during this dwell period. For example, for a 3.0mm semi-compliant PEBAX balloon, the pressure is reduced from 70 psi to 50 psi during this phase IV dwell. Such a reduction preferably results in a lower cross-section and/or protects the balloon material from over-stretching.
After the phase IV dwell period, the balloon is deflated or allowed to return to atmospheric pressure and the iris of the crimper is reduced to the final crimp OD, e.g., 1.01mm or about 30% of the pre-crimp OD of the iris. Such balloon deflation may be performed by opening a valve that provides pressurized gas to the balloon at the same time or prior to the iris diameter being reduced to the final crimped diameter.
The crimper jaws are then held at the final crimp diameter for a dwell time of about 170 seconds or between 100 and 200 seconds while maintaining the crimp temperature (i.e., the scaffold temperature is between 15 degrees below TG and about TG) or without maintaining the crimp temperature. This final dwell period is intended to reduce the amount of stent recoil when the stent is removed from the crimper. The stent was removed immediately after the 170 second dwell and a retaining sheath was placed over the stent to further help reduce recoil. After the final stage of crimping, a leak test may be performed.
To maintain a relatively constant pressure throughout the diameter reduction and dwell period (as shown in the above example), it may be desirable to provide an auxiliary pressure source for the balloon. Indeed, in one embodiment, it has been found that during the diameter reduction there is a pressure drop in the balloon. To address this pressure drop, a secondary pressure source is used to maintain the same pressure during the re-diameter reduction and during the dwell period.
The foregoing example of a preferred crimping process that selectively pressurizes the balloon throughout the crimping step is expected to provide three benefits while minimizing any possible over-stretching of the balloon. The first benefit is improved stent-balloon retention. By maintaining a relatively high pressure in the balloon during most of the crimping step, more balloon material should be disposed between the struts of the scaffold than would be the case if crimping were performed without balloon pressurization or only after a significant reduction in scaffold diameter, as the balloon material is more compressed into the scaffold. Further, it is contemplated that the balloon material is made more compliant by substantially removing the folds prior to any diameter reduction. Thus, more balloon material can expand between the struts rather than being squeezed between the stent and the catheter shaft as the stent is crimped.
A second benefit of balloon pressurization is a more uniform expansion of the crimped stent when the balloon is expanded. When the balloon is inflated from the beginning, the balloon material is more evenly placed around the circumference of the catheter shaft after crimping before any crimping occurs and when there is more space available for the balloon to deploy within the mounted stent. In a preferred embodiment, the balloon is fully inflated and remains in this inflated state for at least 10 seconds prior to any crimping, thereby ensuring that all preformed folds are removed. If the balloon is only partially deployed, as in the case of balloon inflation after the stent has been partially crimped (thereby leaving less available space for the balloon to fully deploy), the fold lines or balloon memory are not removed by balloon pressure, and the presence of the folds or partial folds is believed to cause the balloon material to shift or displace during crimping, resulting in a more uneven distribution of the balloon material around the circumference of the catheter shaft after crimping.
A third benefit is to avoid out-of-plane twisting or overlapping stent struts, which can lead to a reduction in strength, cracking or breakage in the struts. As previously mentioned, the use of an inflated balloon support stent within the crimper is believed to counteract or reduce any tendency of the struts to become misaligned.
When balloon pressure is selectively controlled, the benefits described above can be achieved without the risk of the balloon material being overstretched during crimping. Referring to FIG. 3B, a pressure range of 20-70 psi is provided. In the case of the balloon used in this example, the upper end of this pressure range forms a fully inflated balloon and can remain in the first three stages. For the next phase IV, the balloon pressure was reduced to 50 and 20 psi. It has been found through several tests that maintaining a constant and consistent fully inflated balloon pressure until stage IV begins or after the crimped scaffold reaches about 1/2 degrees f of the original scaffold diameter, then the pressure drops slightly, providing a good balance of stent retention, uniform expansion, low cross-section, uniform crimping, and avoidance of damage to the balloon material.
As previously mentioned, there are three possibilities for curling: two balloons were used-balloon a and balloon B. Balloon B was used for pre-crimp step (a) and balloon a (used with the delivery system) was used for final crimp. Second, only one balloon (balloon a) was used for the entire crimping process including verification of the alignment check. In this case, the stent inner diameter is larger than the fully or over-inflated balloon a. As such, there is a shift on the balloon during pre-crimping. Third, only one balloon (balloon a) was used for the entire crimping process without verification of the alignment check. In this case, the balloon used in the delivery system has a fully or over-inflated state with an inner diameter approximately equal to the inner diameter of the stent. These various embodiments are described further below.
In some embodiments, a process is described by fig. 17A-17B and the examples described above, with the following exceptions. Two balloons are used-in addition to the balloon of the catheter (balloon a), a sacrificial balloon or secondary balloon (balloon B) -as opposed to just balloon a in the above example of the preferred embodiment. Balloon B is a balloon having a nominal inflated balloon diameter greater than balloon a, or balloon B can be over-inflated to a larger diameter than balloon a. Balloon B was used for stages I and II. The balloon B is selected to have a fully expanded diameter that is equal to or slightly larger than the initial inner diameter of the stent. One advantage of this alternative embodiment is that the scaffold is supported by the balloon throughout the crimping process (in contrast to the example above, where balloon a provides little or no radial support to the scaffold due to the gaps in stage I). After stage II, the scaffold is removed from the crimper and balloon B is replaced by balloon a. Thereafter, the crimping process continues as previously described.
The above description of illustrated embodiments of the invention, including what is described in the abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed, except as described in the abstract, but rather as described in the abstract. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification.

Claims (15)

1. A medical device, comprising:
a thin-walled stent having a proximal portion and a distal portion formed from a web of rings interconnected by links, wherein each ring has a plurality of peaks, wherein a peak is one of a U-crown, a Y-crown, and a W-crown, the wavelength corresponds to the wavelength of a sine wave equal to the distance between adjacent peaks of the ring, and each ring extends circumferentially in an undulating fashion along a vertical axis B-B perpendicular to the longitudinal axis a-a;
a marker link extending between a first and second of the rings, the marker link including a structure having an aperture and a radiopaque material received in the aperture;
wherein the marker link forms a first ring Wcrown with the first ring and a second ring Ycrown with the second ring, the first ring Wcrown corresponding to a first peak;
wherein a first wavelength of the first ring measured from the first peak to an adjacent second peak is greater than a second wavelength of the first ring measured from an adjacent second peak to an adjacent third peak; and
wherein the marker link comprises an aspect ratio AR between 4 and 5, wherein AR is defined as the maximum width of the marker link divided by the wall thickness of the marker link;
wherein the thin-walled stent is configured to include an outer diameter of D-min; and wherein
D-min=(1/π)×[(n×strut_width)+(m×link_width)]+2*t,
"n" is the number of struts in the ring,
"strut _ width" is the width of the brace,
"m" is the number of links abutting adjacent rings,
"link _ width" is the width of the connecting rod, an
"t" is wall thickness.
2. The medical device of claim 1, wherein the marker link includes a first link portion extending from the construct to the first ring Wcrown and a second link portion extending from the second ring Y crown to the construct, wherein a width of the first link portion is greater than a width of the second link portion.
3. The medical device of claim 2, wherein the length of the first shaft portion is less than the length of the second shaft portion.
4. The medical device of any of claims 1-3, wherein the structure includes a first hole and a second hole, each hole containing the radiopaque material, wherein the first hole and the second hole are aligned parallel to axis A-A.
5. The medical device of claim 1, wherein the proximal marker link has a first end and a second end, and the W crown has a first width formed by the first end and the Y crown has a second width formed by the second end, wherein the second width is less than the first width.
6. The medical device of claim 5, wherein crown width B1 is 350% to 400% greater than crown width B2.
7. The medical device of claim 1, wherein the first wavelength of the first loop is longer than the wavelength of the second loop.
8. The medical device of claim 1, wherein the first ring has n peaks and n wavelengths, wherein n is at least 6 and no more than 12, and wherein the first and second wavelengths measured from above and below the first peak and the first peak, respectively, are greater than any of the remaining n-2 wavelengths of the first ring.
9. The medical device of claim 8, wherein all remaining n-2 wavelengths have the same length.
10. The medical device of claim 1, wherein a maximum width of the structure, measured along axis B-B, is greater than a maximum width of a link extending between the second loop and a third loop adjoining the second loop.
11. The medical device of claim 1, wherein the marker link includes a first link portion extending from the construct to a W crown and a second link portion extending from a Y crown to the construct, a length of the first length portion being less than a length of the second link portion.
12. The medical device of any of claims 1, 10, or 11, wherein the structure comprises a first hole and a second hole containing a radiopaque material, wherein the first hole and the second hole are aligned parallel to axis a-a.
13. The medical device of any of claims 1-3 or 5-11, wherein the first loop is connected to the second loop by a marker link and peaks of the first loop are spaced apart from peaks of the second loop by a first distance,
the second ring is connected to a third ring by a non-marker link and the peaks of the second ring are spaced apart from the peaks of the third ring by a second distance,
and the first distance is greater than the second distance.
14. The medical device of any of claims 1-3 or 5-11, wherein the stent has a wall thickness of 100 microns.
15. The medical device of claim 1, the marker link comprising an aspect ratio AR of 4.5.
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US14/973,632 2015-12-17
US14/973,633 US9861507B2 (en) 2015-12-17 2015-12-17 Thin-walled scaffolds having modified marker structure near distal end
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