Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
  • A61F2002/91508—Stents 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 difference in amplitude along the band
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
  • A61F2002/91516—Stents 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
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
  • A61F2002/91533—Stents 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 characterised by the phase between adjacent bands
  • A61F2002/91541—Adjacent bands are arranged out of phase
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
  • A61F2002/9155—Adjacent bands being connected to each other
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2/00—Filters 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
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents 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
  • A61F2/91—Stents 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
  • A61F2/915—Stents 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
  • A61F2002/9155—Adjacent bands being connected to each other
  • A61F2002/91566—Adjacent bands being connected to each other connected trough to trough
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS 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
  • A61F2230/00—Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
  • A61F2230/0002—Two-dimensional shapes, e.g. cross-sections
  • A61F2230/0028—Shapes in the form of latin or greek characters
  • A61F2230/0054—V-shaped

Definitions

• the intravascular stent functions as scaffolding for the lumen of a vessel.
• the scaffolding of the vessel walls by the stent serves to: (a) prevent elastic recoil of the dilated vessel wall; (b) eliminate residual stenosis of the vessel, a common occurrence in balloon angioplasty procedures; (c) maintain the diameter of the stented vessel segment slightly larger than the native unobstructed vessel segments adjacent the stented segment; and (d) as indicated by the latest clinical data, lower the restenosis rate.
• the conventional stent designs suffer in varying degrees from a variety of drawbacks including: (a) the inability to negotiate bends in vessels due to columnar rigidity of the unexpanded stent; (b) the lack of structural strength, both radial and bending, of the unexpanded stent; (c) significant foreshortening of the stent during expansion; (d) limited stent length; (e) constant expanded stent diameter; (f) poor crimping characteristics; and (g) rough surface modulation of the unexpanded stent.
• stents are made of wire which is wound and bent into desired configurations
• stents may also be formed using thin-walled tubes that are laser cut, or otherwise formed to allow the tubes to be compressed into a smaller diameter for delivery to a desired location within a body lumen.
• Such stents commonly referred to as tubular stents
• tubular stents provide advantages in terms of increased torsional stability and hoop strength as compared to stents formed from wires.
• tubular stents typically exhibit limited longitudinal flexibility which can limit delivery through tortuous pathways and their deployment in curved body lumens.
• in-stent restenosis consists predominantly of neointimal growth rather than the combination of neointima, recoil and downsize remodelling seen after the balloon angioplasty.
• the degree of restenosis is related to the extent of damage done at the time of implantation.
• the composition of the neointima of in-stent restenosis is similar to that seen in balloon angioplasty, and includes vascular smooth muscle cells and inter-cellular matrix.
• a stent In trying to draw any conclusion from the data available about the "ideal" stent, a pattern is starting to emerge. Whilst preserving the desirable characteristics of low profile, trackability, conformability and visibility, a stent should have many, closely spaced struts giving good, well-distributed radial strength.
• the inter-strut connections whilst allowing for even balloon expansion and access to side-branches, should form a close meshwork which prevents large spaces from opening up between the struts, or from one strut protruding radially beyond its neighbours. The forces for expansion should be distributed evenly so that the stent expands symmetrically, without eccentrity.
• the diameters of some preferred stents, when in the compressed state for delivery to a desired location within a body lumen is typically from about two to about three times less than the diameter of the stents when in their expanded state.
• typical stents may have a compressed external diameter of about 1 millimeter to about 3 millimeters for delivery and an expanded external diameter in a body lumen of about 3 millimeters to about 15 millimeters when released from compression in a large arterial vessel.
• the metal surface coverage as a function of stent diameter is calculated by dividing the total vessel contact metal surface area of the stent structure by the surface area of the vessel at any given stent/vessel diameter. There is inverse relationship between the metal surface coverage and the stent expansion (the more expansion of the stent, the less metal surface coverage).
• the two most important features of the coronary stent are basic to its use : flexibility is required only during insertion and until deployment of the stent at the target lesion. Rigidity is required to supply long term support to the vessel wall, but only from the moment of deployment and on.
• Iris stent which is a slotted tube stent made of 316L stainless steel by Uni-Cath Inc. of Saddle Brook, New Jersey, U.S.A.
• Albert Tashji published in the
• the NIR stent by SCIMED MEDTRONICS (SciMed Life Systems, Inc. of Maple Grove, MN, U.S.A. and Medtronics, Inc. of Minneapolis, MN, U.S.A.) is a multi-cellular slotted tube design made of 316L stainless steel.
• the multi-cellular design comes in two types to cover different vessel diameters.
• the 7-cell circumflex unexpanded stent will expand by different size balloons to cover vessel diameters that range from 2.5mm to 3.5mm.
• the metal to artery percentage ratio for the 7-cell will range from 24% at 2.5mm to 14% at 3.5mm expansion and the stent foreshortening ranges from 7% at 3.5mm to 14% at 4.0mm expansion.
• a second stent is provided where the external diameter of the circumflex unexpanded stent is increased to 9-cell in order to expand up to 5mm.
• the metal to artery percentage ratio for the 9-cell will range from 14% at 3.0mm to 11% at 5.0mm expansion and the stent foreshortening ranges from 7% at 3.5mm to 14% at 5.0mm expansion (PMA application # P980001 , published by the FDA in August 11, 1998).
• the drawback of the increase of the external diameter of the unexpanded stent will effect the flexibility, because there is inverse relationship between the external diameter and the flexibility of the unexpanded stent.
• one object of the invention is to provide a flexible stent which can be easily delivered through meandering and narrow arteries or other body lumens.
• Another object of the invention is to provide the stent as stated above, which can substantially prevent shortening of the entire length of the stent when it is expanded. It is further objection of the present invention to provide a stent which does not substantially change in length or at least does not reduce in length as the stent diameter expands during balloon expansion.
• a further object of the present invention is to provide a stent with a low profile when crimped over a delivery balloon of the stent assembly.
• an intravascular tubular stent expandable between a first, constricted state and a second state of greater expanded diameter; the stent comprising in its constricted state: a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising at least one functional unit having a bendable j oint from which a pair of arms extend, said arms converging toward their ends distal the bendable joint so as to form an elongate converging opening therebetween; and each pair of adjacent radially expandable rings being connected to each other at at least one location.
• an intravascular tubular stent expandable between a first, constricted state and a second state of greater expanded diameter; said stent comprising in its constricted state: a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising one or more U- shaped elements having a bendable joint from which a pair of arms extend generally parallely, said arms defining therebetween a generally constant width opening which opens away from said bendable joint, said constant width opening being arranged in a diagonal orientation with respect to the longitudinal axis of the stent; and each pair of adjacent radially expandable rings being connected to each other at at least one location.
• a self-compensating, radially expandable tubular stent comprising: a plurality of interconnected radially expandable rings each formed of a plurality of circumferentially extendable elements each consisting of one or more over-parallel U-shaped elements having an elongate converging opening defined between converging arms thereof.
• the design geometry of the subject stents is such that substantially no shortening of the stent occurs throughout expansion and over the viable working range of the stent.
• Fig. 1A is a schematic drawing illustrating a tubular stent in its unexpanded, pre- deployment state
• Fig. IB is a schematic drawing similar to that of Fig. A, but showing the stent in a radially expanded state
• Figs. 2 A to 2C are schematic drawings showing a flattened portion of the cylindrical contour of the various tubular stents
• Figs. 3A through 31 are schematic drawings showing various stent elements for describing their mechanics during expansion
• Fig.4A is a schematic showing a flattened portion of the cylindrical contour of a prior art stent
• Fig. 4B is a schematic of a flattened portion of a stent in accordance with the present invention
• Fig. 4C is an illustration of the stent portion show in Fig.4B but in its expanded state.
• Figs. 5 to 15 are schematic drawings showing alternate embodiments of the stent according to the present invention as a flattened portion thereof;
• Fig. 16A is a magnified plan view of a dissected and laid flat stent prototype made in accordance with the present invention
• Fig. 16B is a greatly enlarged detail section of Fig.
• Fig. 16A is a schematic showing a flattened portion of the stent of Fig. 16A but shown in its expanded state;
• Figs. 17 to 19 are schematic drawings showing further stent embodiments made in accordance with the teachings of the invention.
• FIG. 1 A illustrates schematically a simple form of a stent 10 shown in its constricted state, i.e. prior to the deployment and expansion.
• the stent 10 comprises a plurality of interconnected radially expandable rings 12 arranged coaxially so as to form a generally tubular structure having a longitudinal axis 14.
• Each pair of adjacent rings 12 is interconnected by at least one interconnection member 15.
• the stent of the present invention is operable with two or more such rings 12, the number of which is generally dependent on specific structure of the rings and how they are interconnected as well as the desired length of the stent.
• Each ring 12 comprises a series of expandable elements 16 connected together in a circular contour.
• Fig. IB in response to the radially outwardly directed expansion force of a pressurized balloon inserted through the ring 12, each expansion element 16 expands along the generally increasing circumferential contour of the stent 10'.
• Figs. 2 A, 2B and 2C show, for explanatory purposes, specific examples of portions of stents 10A, 10B and IOC, laid flat for illustrative purposes.
• Stents 10A, 10B and IOC comprise a plurality of coaxially-arranged annular rings 12.
• Each ring 12 consists of a series of connected elements 16 which are circumferentially expandable. Adjacent pairs of rings 12 are interconnected by interconnecting elements 15 which can be generally linear as shown or can themselves be expandable or contractible longitudinally with respect to the axis of the stent in response to the expansion of the rings 12.
• interconnecting elements 15 can be generally linear as shown or can themselves be expandable or contractible longitudinally with respect to the axis of the stent in response to the expansion of the rings 12.
• the aforementioned stents 10A, 10B and IOC and, in particular, the extendable elements 16, can be considered to comprise one or more "functional units” each of which, roughly speaking, is an element that doubles-back on itself so as to form a pair of "arms” which are attached at one end and separated at their other thus resulting in a "U", "V” or "C” shape, for example.
• these functional units are U-shaped and are oriented such that their "arms” or their “openings” are disposed either parallel with or transverse to the stent axis 14.
• FIG. 3A shows a functional unit 20A of length L, having a pair of generally parallel arms 22,24 connected by a deformable or bendable joint 26.
• the arms 22,24 are spaced apart a circumferential distance C, by an opening 28. Opening 28 as well as arms 22,24 are disposed generally parallel with the longitudinal axis 14 of the stent.
• many prior art stents utilize such parallelly-oriented functional units or variations thereof in their construction, including Applicant's prior U.S. Patent No. 5,755,776, issued May 26, 1998 and entitled "Permanent Expandable Intraluminal Tubular Stent", which is also incorporated herein by reference.
• 3B demonstrates the changes to the functional unit 20A' during radial expansion of the stent.
• initial deformation takes place in the bendable joint 26 and both the arm members 22,24 move diagonally away from each other in the opposite (i.e. circumferential) direction which results in an increase of the circumferential distance C,' which results in an overall increase in the circumference of the stent 10 during expansion.
• the length L of the functional unit 20A will be reduced to a length L,' which, in turn, results in overall foreshortening of the stent 10.
• a diagonally- oriented functional unit 20C in which the arm members 22,24 have a diagonal orientation with respect to the longitudinal axis 14 of the stent 10.
• the arms 22,24 are connected by a bendable joint 26 also arranged diagonal to the longitudinal axis 14 of the stent 10.
• the functional unit 20C has a length L 3 and the ends of the arms 22,24 are separated a circumferential distance C 3 .
• arm members 22,24 of the functional unit 20C move diagonally away from each other in the opposite direction which results in increase of the circumferential distance C 3 ' which, in turn, results in overall increase in the circumference of the stent 10 during expansion.
• the length L 3 ' of the functional unit 20C will be at least be maintained with respect to initial length L 3 or non-significantly reduced which will result in practically no foreshortening of the stent 10 during expansion.
• FIG. 3G Another alternative to prevent foreshortening of the functional unit is shown in Fig. 3G in which the functional unit 20D having a length L 4 has its two arm members 22,24 angled towards one another each at an angle ⁇ from parallelity with the stent axis 14 so that the opening 28 is narrower at the ends of the arms 22,24 distal the bendable joint 26 than at their proximal ends.
• This arrangement is termed herein as "over-parallel”.
• the advantage to this over-parallel arrangement is that where the ends distal the bendable joint are spaced an initial circumferential distance C 4 , circumferential expansion initially opens the arms 22,24 through to parallelity as shown in Fig.
• Figs. 4B and 4C illustrate the principle of the over-parallel functional unit 20D of Fig. 3G as applied to the substantially rectilinear stent design 40 as shown in Fig. 4A, which is derived from Applicant's aforementioned U.S. Patent No. 5,755,776.
• Stent 40 comprises a plurality of circular rings 12 arranged coaxially with respect to stent axis 14.
• Each ring 12 comprises a plurality of circumferentially expandable elements 16 arranged in a generally serpentine or square wave-form pattern about the cylindrical contour of the stent.
• the arrangement of circumferentially expandable elements 16 in one ring 12 is such that the adj acent ring 12 is the mirror opposite in the axial direction.
• the openings 28 of the expandable elements 16 of one ring 12 oppose the openings 28 of the expandable elements 16 of an adjacent ring 12, whereas the "joints" 26 of the expandable elements 16 are disposed immediately adjacent the joints 26 of the adjacent ring 12.
• the stent 40 resists reduction in length upon radial expansion as explained in Applicant's aforementioned U.S. Patent No. 5,755,776.
• the joints 26 between the pairs of arms 22,24 are rounded and the arms 22,24, which are generally linear, are angled toward one another so as to form an expandable element 16 with a convergent opening 28 which is the same as the over-parallel functional unit 20D of Fig. 3G.
• the expandable element 16 alternatingly repeats itself so as to form a serpentine or sinusoidal ring 12.
• the arm 22 for one expandable element 16 is shared as one arm 22 of the circumferentially adjacent expandable element 16 as shown in Fig. 4B.
• Interconnecting members 15 connects the bottom 42 of one expandable element 16 to an opposed expandable element 16 so as to function in the same manner as the interconnecting member 15 of the stent 40 of Fig.
• stents 50 of Fig. 4B are shown in Figs. 5 and 6 as stents 60,70 in their compressed (i.e. unexpanded), pre-deployment state.
• the ring interconnecting member 62 essentially takes the place of an adjacent pair of expandable elements 16' as shown in stippled lines.
• interconnecting member 62 serves to reduce the longitudinal reduction of the stent 60.
• the presence of the over-parallel functional units 20D serve to further reduce the amount of foreshortening.
• the stent 70 of Fig. 6 is provided with a relatively short interconnection member 64s between adjacent rings 12. Enhanced axial flexibility is important in the undeployed stent to enable the stent to be delivered to a desired location via a tortuous vessel.
• the stents 50,60,70 shown in Figs. 4B,5, and 6 comprise a plurality of the over-parallel functional units 20D disposed generally parallel with respect to the longitudinal axis 14 of the respective stent (i.e. the openings 28 are aligned generally parallel as shown in Fig. 3G).
• Applicant has found as explained in his aforementioned International Application No. PCT/CA99/00632, that by orienting at least some of the roughly linear components of the circumferentially expandable elements 16 in the circumferential direction, such as is shown in Figs. 2A-2C, self-compensation of the longitudinal shortening of the stent occurs due to the longitudinal expansion of each ring 12 coupled with the reduction in distance between adj acent rings.
• Fig. 7 one embodiment of the invention which includes a plurality of rings 12 each comprised of a series of circumferentially expandable se ⁇ entine elements 16.
• Each expandable element 16 is comprised of a plurality of over-parallel functional units 20E oriented generally circumferentially or perpendicular to the longitudinal axis 14 of the stent 80.
• Adjacent rings 12 are interconnected at selective locations 82 whereat the bendable joint 26 of one over-parallel functional unit 20E is integrally formed, fused or otherwise attached to the bendable joint 26 of an adjacent over-parallel functional unit 20E.
• the external apexes of adjacent bendable joints 26 are attached.
• each expandable element 16 is connected to the next in the series by way of a further over-parallel functional unit 20F oriented generally parallel to the axis 14.
• Fig. 8 shows a stent 90 which is a variation of the stent 80 embodiment of Fig. 7 having substantially identical rings 12 comprised of a series of expandable elements 16, each being a horizontal mirror image to the next in the series.
• the rings 12 themselves are vertical mirror images of the adjacent ring 12.
• the rings 12 in this embodiment are interconnected in the same manner as the stent 50 of Fig.4B, that being an interconnecting member 15 which extends from the bottom of one axially aligned, over-parallel functional units 20F to the bottom of an opposed over-parallel functional unit 20F.
• the stent 100 shown in Fig. 9 is similar to the stent 80 of Fig. 7 except that the arms 22A,24A of the circumferentially aligned over-parallel functional units 20E which are on the outermost sides of each expandable element 16 are circumferentially aligned. Between circumferentially adjacent expandable elements 16, an axially-aligned functional unit 20A, such as shown in Fig.
• the stent 110 shown in Fig. 10 comprises a plurality of rings 12, each identical to its adjacent ring 12. While as with the Fig. 7 and Fig. 8 embodiments, adjacent bendable joints 26 are interconnected by member 15, due to the geometry, the bottom of one axially-aligned over- parallel functional unit 20F is attached by member 15 to the apex of an adjacent axially- aligned over-parallel functional unit 20F'.
• the interconnection of the adjacent rings 12 can take on various forms as already shown in Figs. 7 to 10 and as shown in Figs. 11 to 15.
• selective adjacent portions 120 of circumferentially expandable elements 16 of adj acent rings 12 may be integrally formed, fused or otherwise attached to form the connection.
• Fig. 11 selective adjacent portions 120 of circumferentially expandable elements 16 of adj acent rings 12 may be integrally formed, fused or otherwise attached to form the connection.
• an interconnecting element 122 extends between a portion of one expandable element 16 of one ring 12 and a portion of another expandable element 16' in an adjacent ring 12'.
• the expandable element 16 is not axially adj acent the expandable element 16'.
• the interconnecting member need not be linear and may take a variety of different shapes to promote better axial flexibility of the stent, maintaining the axial length of the stent, and/or to provide additional vessel wall support and, hence, greater metal coverage.
• the interconnecting member 122 is serpentine or N-shaped which is geared toward promoting separation between rings 12,12' during expansion. In Fig.
• interconnecting member 124 is shown as triple-S-shaped which tends to increase the metal content, increase the radial strength and serves to fill the larger gaps for more complete support.
• the interconnecting member 126 is disposed between portions of adjacent expandable elements 16 of adjacent rings. In this case, interconnecting member 126 is shown as U-shaped but any one of a variety of shapes may be employed.
• Fig. 15 illustrates more complex interconnecting mechanisms 128,130.
• Interconnecting mechanism 128 comprises a first interconnecting member 128 A disposed between portions of adjacent expandable elements 16 of adjacent rings 12,12' and a second interconnecting member 128B disposed between portions of adjacent expandable elements
• Interconnecting mechanism 130 comprises a first interconnecting member 130A disposed between non-adjacent portions expandable elements 16 of adjacent rings 12', 12 and a second interconnecting member 130B disposed between non-adj acent portions of adj acent expandable elements 16 of adjacent rings 12 ',12. Both the interconnecting members 130A,130B are N- shaped with their central leg portions crossingly attached.
• the interconnecting mechanisms 128,130 serve to increase the metal coverage, which will give more radial support and reduce the gaps between the struts/members, and can be designed to limit the radial expansion of the stent so as to reduce the risk of stent rupture by overinflation.
• Fig. 16 A shows a complete portion of a stent 140 (as laid flat) in accordance with a prototype of the present invention which is similar to the stent portion 100 of Fig. 9 except that the expandable element 16 includes an additional circumferentially-oriented, over-parallel functional unit 20E.
• adjacent rings 12 are interconnected by a relatively short interconnecting member 142 to facilitate axial flexing.
• the stent 140 provides substantial metal coverage when in its unexpanded state shown in Fig. 16A.
• the length L 15.851mm and the distance C, which is the circumference is 4.393mm which results in a tubular stent of approximately 1.37mm diameter.
• Fig. 16B illustrates an enlarged section of the stent 140 of Fig. 16 A.
• Table 2 sets out the length L and radius R dimensions (in mm) as measured:
• the thickness of the material i.e the stent's tubular wall thickness is on the order of about 0.05-0.2mm.
• Fig. 16C shows a portion of the stent 140 in its expanded form as 140'.
• the expandable elements 16' have started to move diagonally and the axially-oriented functional units 20A' have expanded circumferentially to an "under-parallel" disposition.
• the rings 12' are prevented from separation by interconnecting members 142'.
• the expansion causes a tensile force component to be exerted along the expandable element 16', causing the individual functional units 20E 'expand from their originally over-parallel disposition to parallel as shown in Fig. 16C and with sufficient expansion, to an under-parallel disposition.
• Table 3 sets out the results of radial expansion testing the stent 140.
• Table 3 As can be seen from Table 3, the length of the stent 140 remains the same over the range from its nominal, unexpanded diameter of 1.37mm to 4mm. These results can be compared with the results of Uni-Cath, Inc.'s Iris stent as shown in Table 1 , which show stent length reduction as expansion increases. In addition, the stent 140 retains acceptable metal coverage over the expansion range.
• a stent 150 comprising a plurality of similar rings 152.
• Each ring 152 consists of an alternating series of over-parallel functional elements 20G which are arranged diagonally with respect to the longitudinal axis 14 of the stent 150.
• Each ring 152 forms a separate oblique cylinder and is not part of a "helical winding", and accordingly, the end rings 152 are not as prone to splaying as would be the case with a free end portion of a helical winding.
• adjacent rings 152 are interconnected with an interconnecting member 154 between opposed bendable joints 156.
• the interconnecting members can be attached in an number of ways, such as for example, bottom-to-bottom as shown, apex-to-apex as shown in Fig. 16A, or apex-to-bottom as shown in Fig. 10.
• the length of the connecting member 164 between adjacent rings 162 can be reduced as aforesaid and as illustrated in Fig. 18.
• stent 170 of Fig. 19 is constructed of a plurality of obliquely disposed rings 172.
• Each ring 172 consists of a series of circumferentially expandable elements 16 in this case connected to the next expandable element in the series by a diagonally-disposed functional unit 20C.
• Each expandable element comprises one or more diagonally-oriented functional units 20C which in this case are disposed generally at right angles to the diagonally-disposed functional unit 20C.
• Selected apexes of adj acent bendable joints 176 of adj acent rings 172 may be attached at 174 to form the ring interconnections or the interconnecting can be accomplished in any of the manners discussed in this application or in Applicant's aforementioned International Application No. PCT/CA99/00632.
• the stents described herein are preferably fabricated from biocompatible, low memory, more plastic than elastic material to permit the stent to be expanded and deformed, yet sufficiently rigid to permit the stent to retain its expanded and deformed configuration with an enlarged diameter and also to resist radial collapse.
• stents in accordance with the teachings herein may be expanded up to about four times their original constricted diameters yet still have desirable properties of good axial flexibility in the constricted state and resistance to radial collapse and comprehensive wall support in the expanded state.
• stents may be provided for example in nominal diameters d of about 1mm, 1.5mm, and 2mm which, depending on the specific structure, may be expanded to 4mm, 6mm or 8mm, respectively, which should enable a minimum number of stents to be employed in most situations.
• the stents of the present invention are operable over their entire range because they deform substantially continuously under application of an radially outwardly directed force. Upon removal of the force, deformation halts and the stent remains sufficiently rigid to withstand the radial force of the wall which it supports.
• Suitable materials for the fabrication of the tubular stent would include silver, tantalum, stainless steel (316 L), gold, titanium, NiTi alloy or any suitable plastic materials such as thermoplastic polymers. Any medically-suitable metal which is capable of yielding plastically under the typical forces of a balloon catheter could also be employed.
• the stent may be made of a radioactive material or irradiated with a radioactive isotope.
• the radioactive isotope may be a beta particle emitting radioisotope.
• cancer cells in and around the stent can be deactivated or killed.
• the stent can be coated with materials that prevent cell overgrowth.
• the stent may be coated with an anticoagulating medication substance, such as heparin, and/or a bioabsorbable material. Accordingly, when the stent is used in a blood vessel, blood clotting can be prevented. Also, the stent may have pores, indentations or a roughened surface capable of absorbing or retaining a drug therein/thereon for slowly releasing the same over time. Thus, when the stent with a drug is implanted in the body lumen, the drug can slowly released in the body lumen.
• an anticoagulating medication substance such as heparin
• the end rings can be formed from a radio-opaque material, such as gold, silver or platinum, which allows both ends of the stent to be clearly visible through a medical imaging device during or after implantation of the stent within a body lumen of the patient.
• a radio-opaque material such as gold, silver or platinum
• the stent is preferably formed by laser cutting technology wherein the pattern is cut into a cylindrical section of the appropriate material.
• Other suitable methods may be used, for example, the stent can be formed by an etching technique. Namely, a pattern of the rings and the interconnecting members are coated on a cylindrical metal member, which is etched in an acid solution. Then, un-coated portions are removed.
• the thickness of the material i.e the stent' s tubular wall thickness is on the order of about 0.05-0.2mm.
• the cross-sectional configuration of the material can be varied, although it will likely depend upon the manner in which the stent is manufactured. For, example, using laser cutting on a piece of tubular material, the resulting members which are disposed in the circumferential direction will have roughly rectangular cross-sections while the members generally parallel to the longitudinal axis will likely have a slightly trapezoidal cross-section if the axis of the laser intersects the axis of the tubular material. A more rectangular cross- section would be obtainable with an appropriate offset of the laser's axis.

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  • 2000-01-21 WO PCT/CA2000/000035 patent/WO2000042946A1/en not_active Application Discontinuation
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