WO2001095976A1 - Stent delivery system - Google Patents

Abstract

This invention is a low profile system for delivery of a medical treatment device, such as a stent (140) in a body vessel lumen. The delivery system includes an inflatable balloon (120) mounted on a balloon catheter (128), an insertion tip (110) secured to the distal end of the balloon (120) or the balloon catheter, (28) and the stent (140), mounted on the balloon (120) proximate to the insertion tip (110). The delivery system is placed into a body vessel within a delivery catheter (130) using an appropriate guiding system. The overall diameter of the delivery system/delivery catheter assembly permits delivery of even relatively large stents into small diameter body vessel lumens, such as those of the pulmonary arteries in a yound child. Methods for use of the delivery system are also provided.

Description

STENT DELIVERY SYSTEM

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to devices for use in interventional cardiology, especially pediatric interventional cardiology. More specifically, the invention relates to catheter- based delivery systems for intravascular placement of medical treatment devices, such as endoprotheses, commonly referred to as stents.

History of the Related Art Angioplasty involves enlarging an artery or vessel by expansion of a balloon, followed by placement of a stent to maintain the patency of the treated vessel. Conventionally, stent delivery systems consist of several concentrically disposed components, each of which adds to the overall diameter of the device. Such components typically include the stent itself (also known as an endoprothesis); a retractable sheath or delivery catheter; a dilater catheter, a guidewire or other guiding assembly; and, for mechanical expansion of the stent, a balloon and balloon catheter.

Stent delivery is often accomplished with a three catheter system. First, a delivery catheter is inserted into through the skin, into a vessel and is moved to the site of the lesion with the aid of a dilater catheter and guide assembly. The dilater catheter is carried within the lumen of the delivery catheter and is designed to provide a smooth transition for insertion of the delivery catheter into the vessel, thereby minimizing the potential for trauma to the vessel walls as the delivery catheter advances through the vessel lumen. Once the delivery catheter is in the vessel, the dilater catheter is removed and a balloon catheter with attached stent (compressed in diameter over the balloon) is inserted into the vessel, via the delivery catheter, and advanced to the lesion to be treated.

Once in place, delivery catheter is retracted, exposing the balloon and stent. The stent is mechanically expanded such as through inflation of the balloon over which the stent is mounted. On expansion, the stent serves as a scaffold to hold the vessel open at the lesioned site. The balloon catheter and the delivery catheter are then removed from the body.

Use of a dilater catheter based system for stent delivery increases catheter laboratory time (i.e., the time to perform the technique), and entails increased manufacturing costs (arising from creation of a separate catheter). Also, because the balloon catheter with associated compressed stent must be passed though the length of the delivery catheter, the lumen of the delivery catheter must necessarily be of a sufficiently larger diameter to accommodate the diameter of the stent/balloon/balloon catheter assembly. This requirement for increased delivery catheter diameter translates to a larger diameter puncture of the vessel, resulting in increased bleeding when the delivery catheter is removed from the vessel.

Further, the relatively large diameter of a multiple catheter delivery system limits the range of vessels in which the system can be used. In particular, smaller vessels, such as those in small children and infants, or vessels which serve organs (such as the biliary, ileac and renal vessels), can be accessed for angioplasty if diameter of the catheters can be reduced.

SUMMARY OF THE INVENTION

The present invention satisfies this need by providing low profile system for delivery of a medical treatment device ("delivery system") which is relatively easy to manufacture, avoids the need for a dilater catheter, and can be used in vessels as narrow as those found in a small infant.

The delivery system of the invention consists of a system for delivery of a medical treatment device, comprising: a) a balloon having distal and proximal ends; b) an elongated catheter having distal and proximal ends, on which the balloon is mounted ("balloon catheter") so the distal end of the balloon catheter protrudes therefrom; wherein the balloon catheter has one or more lumens therethrough; c) a medical treatment device mounted onto the balloon (hereafter, a "stent"); d) an insertion tip, having a proximal and a distal end, wherein the proximal end is proximate to the stent, and wherein the distal end tapers to form a rounded tip.

In varying embodiments of the invention, the proximal end of the insertion tip is mounted onto the distal end of the balloon, and/or, at its distal end, is attached to or integrally formed as a part of, the distal end of the balloon catheter which protrudes from the balloon.

At least one lumen of the balloon catheter may also serve as a conduit for introduction of inflation medium to the balloon, while another may allow for insertion therethrough of a guidewire, or may be otherwise adapted for use with an alternative guiding assembly.

As a complete assembly for use in a body, the delivery system may further comprise:

(a) a delivery catheter having proximal and distal ends, wherein the distal end is disposed over the balloon and medical treatment device; and,

(b) a guiding assembly, such as a guidewire, for directing the stent delivery system into a body vessel.

In use, the delivery system is inserted into a body vessel and advanced therethrough (using the guiding assembly) to the target lesion. While the stent/balloon assembly of the balloon catheter is enclosed in the distal end of the delivery catheter, the insertion tip protrudes beyond the catheter and into the vessel lumen. In this fashion, the balloon catheter with attached balloon/stent and the delivery catheter are together inserted into the body and the vessel, with the insertion tip providing a smooth transition of the delivery system assembly through the vessel.

Once the stent/balloon assembly is in position at the target lesion (the insertion tip having advanced beyond the lesion), the delivery catheter is retracted to expose the stent. The balloon is inflated to expand the stent to the desired degree (fully, or in stepwise fashion to permit adjustments in the position of the stent). After the stent is fully expanded, the balloon catheter is retracted from the body, with the insertion tip still attached to the now deflated balloon or, in alternative embodiments, still attached to, or integrated within, the distal end of the balloon catheter.

Thus, according to the invention, the need for one element of a conventional, multiple catheter stent delivery system— the dilater catheter used to provide a tapered end for insertion of the delivery catheter into a body vessel— is eliminated. This provides many advantages including an overall reduction in diameter of the system for a given balloon size, because the delivery catheter no longer needs to accommodate passage of the sent/balloon/balloon catheter assembly through the entire length of the delivery catheter. Availability of the inventive delivery system therefore decreases manufacturing costs, shortens the time necessary to perform the stent placement procedure, increases the numbers of potential pediatric candidates for stent-based repair of vascular defects, and provides means to smoothly deliver stents into virtually any diameter body vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a partial cross-sectional, elevation view of an over-the-wire embodiment of the delivery system of the invention, including a partially retracted delivery catheter, wherein the stent is in a compressed state.

Figure 2 depicts a partial cross-sectional, elevation view of an over-the-wire embodiment of the delivery system of the invention, including a partially retracted, multi-profile delivery catheter, wherein the stent is in a compressed state.

Figure 3 depicts a partial cross-sectional, elevation view of an over-the-wire embodiment of the delivery system of the invention, including a partially retracted delivery catheter, wherein the insertion tip is formed integral with the distal end of the balloon catheter.

Like numerals refer to like structures in the drawings. DETAILED DESCRIPTION OF THE INVENTION

Stent implantation for treatment of vascular stenoses, such as branch pulmonary artery stenosis (BPAS) in congenital heart disease, is well established. However, the need for relatively large sheaths (9to 11 French, "Fr") for delivery of large stents (dilatable to 18 mm) renders this technique difficult if not impossible in infants and small children. Although smaller stents (dilatable to 10 mm) can be delivered through smaller sheaths, such stents cannot be further expanded to accommodate growth of the arteries to adult size. In addition, stent implantation techniques in which a dilater catheter is used to aid in insertion of the delivery catheter require that the delivery system be of sufficient overall diamater to permit the delivery catheter to encompass the dilater catheter and that the delivery catheter also be of sufficient diameter to accommodate the stent/balloon/balloon catheter assembly. The present invention avoids these limitations of the existing art by providing a balloon catheter which carries an insertion tip, which tip is designed to provide the smooth transition of the delivery system into the vessel which may now be provided by a dilater catheter. This avoids the need for a separate dilater catheter and also allows the balloon/stent of the balloon catheter to be "front loaded" into the delivery catheter. Front loading avoids the requirement for the balloon/stent to traverse the entire length of the delivery catheter, thus reducing the size (diameter) requirements of the delivery catheter.

As described below, with respect to the representative embodiments of the invention illustrated in the Figures, the insertion tip may conveniently be carried by the balloon catheter by mounting the insertion tip directly onto the distal end of the balloon. Alternatively, the insertion tip can be mounted directly onto the balloon catheter, on the portion thereof which protrudes distally from the balloon (e.g. , the distal end of the insertion tip may be secured to the balloon catheter). Also, the insertion tip can be integrally formed (e.g, by extrusion) as part of the balloon catheter, so long as the insertion tip is, at its proximal end, of a diameter larger than that of the balloon catheter, so at least the proximal end of the insertion tip fits securely within the inner diameter of the delivery catheter. Furthermore, the insertion tip may itself comprise a balloon ("second balloon"), mounted on the balloon catheter separate from, and distal to, the stent-carrying balloon ("first balloon"). In this embodiment, the second balloon is formed to taper from its proximate to its distal ends to form an insertion tip, but is otherwise relatively conventional in construction (e.g. , is compressed onto the balloon catheter, and may be inflated, in a manner comparable to the first balloon).

As shown in Figure 1, insertion tip 110 tapers along edge 114 smoothly to its rounded distal end 112. At its proximal end 116, insertion tip 110 is secured to distal end 122 of balloon 120. In Figure 1, balloon 120 is in a deflated state, and is shown tightly compressed (through the formation of multiple folds) to form a cylinder. Securing insertion tip 110 to distal end 122 of balloon 120 can be accomplished by any suitable means, such as by pressure fit, heat setting, or through use of a biocompatible adhesive.

Proximate to proximal end 116 of insertion tip 110 is stent 140. Stent 140 is compressed and secured to balloon 120 (proximate to distal end 122) by conventional means, such as crimping. Any balloon-expandable stent may be used in the invention (e.g., the NIR™ stent sold by Scimed Life Systems, Inc.). The stent will preferably be one whose compression limits are such that the stent can be compressed and crimped securely onto a balloon having an expanded diameter between 1 and 40 mm, more preferably between 2 and 40 mm and even more preferably between 4 and 24 mm.

The balloon is mounted on a balloon catheter 128, having an outer lumen 124, for introduction of inflation medium to the balloon, and an inner lumen 126, for passage therethrough of a guidewire (not shown). Balloon catheter 128 shown is in a conventional "over the wire" configuration, but those of ordinary skill in the art will appreciate that the balloon catheter may also be used in alternative configurations, such as the "single operator exchange," "rapid exchange" and "fixed wire" configurations. In Figure 1, delivery catheter 130 is shown in a partially retracted position, with its distal-most end 132 slightly overlapping proximal end 141 of stent 140. Delivery catheter 130 has a lumen 132 therethrough in which balloon catheter 128, with stent 140 and insertion tip 110 mounted thereon over balloon 120 to collectively form delivery system 150, is slidably disposed.

Insertion tip 110 is shown in Figure 1 adjacent to the balloon, mounted onto the balloon catheter. Insertion tip 110 also can be mounted such that its proximal end overlaps with the distal end of the balloon, and is alternatively attached thereto, provided the overlap does not significantly impair inflation of the balloon. Insertion tip 110 can be manufactured separately from the balloon catheter 128 and then attached to the balloon catheter during the manufacturing process or before use. Attachment can be achieved by methods well known in the art including, for example, the use of biocompatible glues, by a screw type fitting or by forcing the tip onto the end of the balloon. Alternatively, as shown in Figure 3, the insertion tip 310 can be manufactured such that it is attached at its distal end 312 to, and/or made an integral part of balloon catheter 324, so long as the outer diameter of insertion tip 310 is larger than that of balloon catheter 328 and, optionally, distal end 322 of balloon 320, to an extent sufficient to provide a secure fit between the inner diameter of delivery catheter 330, and the outer diameter of insertion tip 310. In all other elements, this embodiment of the invention is similar to the embodiments of Figure 1 or Figure 2, and includes, without limitation, stent 340 which, together with balloon 320 and balloon catheter 328, forms delivery system 350.

The tapered edge 114 of insertion tip 110 (Figure 1) should provide a smooth transition between the inner lumen 126 and the distal-most end 132 of the delivery catheter 130. The tapered edge can be manufactured in a relatively rigid form such as the pointed end of a dilater catheter or may be provided by a separate, second balloon, mounted on the balloon catheter distal to the stent/balloon assembly, which second balloon can be inflated or dilated before use to provide the desired tapered edge. As the design shown in Figure 1 allows for front loading of the balloon/stent with dilater tip, choice of the diameter (ID) of lumen 132 will need focus primarily on the diameter of the balloon catheter with balloon without the stent. Depending on the size of the vessel to be treated, the diameter (ID) of lumen 132 will vary, but most vessels can be treated using delivery catheters ranging in size from 3 Fr to 24 Fr, more preferably from 4 Fr to 14 Fr and even more preferably from 4 Fr to about 8 Fr. For use in small diameter lumens, delivery catheter 130 (or variable diameter delivery catheter 230, described below) preferably has (at its narrowest point), a diameter in the range between and including 4 to 7 Fr. Preferably, walls 136 of delivery catheter 130 will be as thin as possible, while retaining the degree of rigidity required to allow the catheter to be pushed into a body vessel.

For placement in a body vessel lumen, delivery system 150 is retracted into delivery catheter 130 with insertion tip 110 protruding beyond distal end 132 of delivery catheter 130. Serving as a gentle probe, insertion tip 110 is advanced through the vessel lumen, and past the lesion to be treated, along a guidewire (or through use of any suitable guiding mechanism), until distal end 132 of catheter 130 (enclosing stent 140) is in place at the lesion site. Delivery catheter 130 is then retracted to expose stent 140. Through inflation of balloon 120 (all at once, or stepwise to permit adjustments in position), stent 140 is expanded. As balloon 120 is inflated, insertion tip 110 remains attached to balloon catheter

128 and/or balloon 120 (depending on whether one or both points of potential attachment of insertion tip 110 to the balloon or balloon catheter, as described, are utilized). Once the stent is in position and fully expanded, balloon catheter 128 is withdrawn from the vessel lumen, together with balloon 120 (now deflated), and insertion tip 110, by retraction through the bore of now expanded stent 140.

For use in extremely small vessel lumens, a delivery catheter may be used in which the distal-most end (for enclosure of delivery system 150) is of a larger diameter than the proximal remainder of the catheter. For example, as shown in Figure 2, proximal region 234 of delivery catheter 230 has a diameter (ID) of 6 Fr, while distal end 232 has a diameter (ID) of 7 Fr. The elasticity of the vessel walls will allow them to contract to fit around proximal region 254 of delivery catheter 230 after temporarily expanding to give way for passage of distal end 232 therethrough. In this manner, less stress is place on the vessel walls than would be induced by maintaining a larger diameter catheter within the vessel throughout the stent delivery procedure, thereby allowing use of the inventive delivery system in vessels having relatively small diameter lumens. Furthermore, the size of the hole that is made for entry of a given stent is thereby reduced, consequently reducing complications from bleeding.

Conventional methods and materials, known in the art, may be used in the construction of the delivery and balloon catheters of the invention. For example, the catheters may be formed by extrusion, using thermoplastic polymers (such as polyethylene, polyester and polyimide), thermoset polymers, and silicones. Similar materials, of relatively high elasticity (to permit dilation), may be utilized in the manufacture of the dilatable insertion tip of the invention. The insertion tip may also be treated with a biocompatible coating, such as the DuPont acrylic product Teflon^®, to reduce friction as the tip advances through a body vessel.

Those of ordinary skill in the art will also appreciate that the delivery system can be used to advantage for delivery of stents using either small or relatively large catheters. For example, even in adults, the use of a stent/balloon catheter assembly on which an insertion tip is pre-mounted not only simplifies manufacture of the device, but enables the physician to customize the device by matching preferred catheter components to the delivery system of the invention, as desired for use in each given procedure. Thus, in addition to its use in treating lesions in small diameter vessels such as the pulmonary arteries in children, the inventive delivery system may also be used for treatment of lesions in any body vessel including, without limitation, the coronary arteries, pulmonary arteries, pulmonary veins, aorta, carotid arteries, the peripheral vasculature, as well as non-coronary organ-serving vessels, such as the renal, biliary and iliac vessels.

The invention having been fully described, modifications and alternative embodiments may become apparent to those of ordinary skill in the art. All such alterations to the invention described are intended to fall within the scope of the claims. Examples illustrating construction and use of the invention are set forth below. In the Examples, art-accepted meanings are to be ascribed to abbreviations used, unless otherwise specified. The examples should not be construed to limit the scope of the invention, which is defined by the appended claims.

EXAMPLE I

Construction of the Delivery System as Shown in Figure 1

The "dilator-tipped" balloon was created by attaching a dilator tip over the distal tip of a various conventional balloon catheters having balloons of 6, 8, 10, 12 and 14 mm (expanded balloon volume) and each balloon manufactured with a large stent compressed over it (stents dilatable up to 18 mm were from various manufacturers including Palmnz P308 and P188 made by Johnson & Johnson). The dilater tip was cut from the end of a dilater catheter, it was gently heated until soft and the cut end was forced onto the distal end of the balloon catheter. The dilater tipped balloon catheter was then front loaded by passing its proximal end through a long sheath (7 Fr delivery catheter for 6 and 8 mm balloons and an 8 Fr delivery catheter for 10 - 14 mm balloons; manufactured by Cook Medical). After assembly, only the dilatable insertion tip was exposed beyond the end of the delivery catheter.

EXAMPLE II Delivery of a Stent Using the Delivery System of the Invention

The dilatable insertion tip permits a smooth transition for delivery of the stent/balloon delivery system and delivery catheter unit from the skin to the site of stenosis. This method was used to deliver 32 stents (P308 and P188) in 24 human infants and children, ranging is weight from 5.4 Kg to 38.7 Kg.

Stent delivery was successful in all patients treated. 18 stents mounted on 10-14 mm diameter balloons were delivered through 8 Fr sheaths while 14 stents mounted on 6 or 8 mm diameter balloons were delivered through 7 Fr sheaths in the 10 smallest patients (6 & 9 kg). The mean vessel diameter after treatment increased from 4.7 ± 1.9 mm to 9.1 + 2.3 mm and the gradient decreased from 28 ± 19 to 4 ± 5 mmHg (p-value <0.05).

The only complications were balloon perforation during stent inflation in 3. All balloons were removed and the partially inflated stents were implanted in good position with a new balloon without difficulty. No dilator tip dislodged from the balloon during any procedure.

The invention therefore permits delivery of large stents through small sheath catheters safely and effectively, and is particularly advantageous for use in treating infants and small children with BPAS.

Claims

The invention claimed is: 1. A system for delivery of a medical treatment device, comprising:

a) a balloon having distal and proximal ends, relative to the user; b) an elongated catheter having distal and proximal ends, on which the balloon is mounted ("balloon catheter") so the distal end of the balloon catheter protrudes therefrom; wherein the balloon catheter has one or more lumens therethrough; c) a medical treatment device mounted onto the balloon; d) an insertion tip, having a proximal and a distal end, wherein the proximal end is carried on the balloon catheter proximate to the stent, and wherein the distal end tapers to form a tip.

2. The delivery system according to Claim 1, wherein the balloon is dilatable to a diameter of greater than 10 mm.

3. The delivery system according to Claim 1, wherein the balloon is dilatable to a diameter of 10 mm or less.

4. The delivery system according to Claim 1, wherein the medical treatment device is a stent.

5. The delivery system according to Claim 4, wherein the stent is mechanically expandable.

6. The delivery system according to Claim 1, wherein the proximate end of the insertion tip is secured to the balloon, proximate to the stent.

7. The delivery system according to Claim 1, wherein the distal end of the insertion tip is secured to the distal end balloon catheter which protrudes distally from the balloon.

8. The delivery system according to Claim 1, wherein the insertion tip is an integral part of the distal end of the balloon catheter which protrudes distally from the balloon, and wherein further the proximal end of the insertion tip has an outer diameter larger than the outer diameter of the balloon catheter.

9. The delivery system according to Claim 1, further comprising a delivery catheter slidably disposed over the stent and balloon.

10. The delivery system according to Claim 8, further comprising a delivery catheter slidably disposed over the stent and balloon.

11. The delivery system according to Claim 10, wherein the proximal end of the insertion tip fits closely within the delivery catheter.

12. A system for delivery of a medical treatment device, comprising:

a) a first balloon having distal and proximal ends, relative to the user; b) an elongated catheter having distal and proximal ends, on which the first balloon is mounted ("balloon catheter") so the distal end of the balloon catheter protrudes therefrom; wherein the balloon catheter has one or more lumens therethrough; c) a medical treatment device mounted onto the first balloon; d) an insertion tip, having a proximal and a distal end, the insertion tip comprising a second balloon tapering distally to form a tip, which insertion tip mounted onto the distal end of the balloon catheter which protrudes from the first balloon.

13. A method for delivering a medical treatment device into a body vessel lumen, the device consisting of a stent, the method comprising:

(a) slidably disposing the delivery system of Claim 1 within a delivery catheter to enclose the stent within the delivery catheter, with the insertion tip protruding distally therefrom; (b) inserting the delivery system and delivery catheter assembly formed in step

(a) into a body vessel lumen;

(c) advancing the assembly into the lumen until the enclosed stent is in the desired position within the vessel;

(d) retracting the delivery catheter to expose the stent; (e) causing the balloon to inflate so as to expand the stent to a desired degree;

(f) deflating the balloon; and,

(g) retracting the delivery system from the body vessel.

14. The method according to Claim 13, wherein the stent is expanded at the site of a stenosis in the vessel.

15. The method according to Claim 14, wherein the stenosis is a branch pulmonary artery stenosis.

16. The method according to Claim 13, wherein the individual in whom the stent is delivered is a child.

17. The method according to Claim 16, wherein the child is an infant.

18. The method according to Claim 13, wherein the individual in whom the stent is delivered is an adult.

19. The method according to Claim 13, wherein the body vessel into which the stent is delivered is selected from the group of vessels consisting of the coronary arteries, the pulmonary arteries, the carotid arteries, the peripheral vasculature, and vessels serving non-coronary organs.

20. A method for delivering a medical treatment device into a body vessel lumen, the device consisting of a stent, the method comprising: (a) slidably disposing the delivery system of Claim 12 within a delivery catheter to enclose the stent within the delivery catheter, with the insertion tip protruding distally therefrom;

(b) inserting the delivery system and delivery catheter assembly formed in step (a) into a body vessel lumen; (c) advancing the assembly into the lumen until the enclosed stent is in the desired position within the vessel; (d) retracting the delivery catheter to expose the stent;

(e) causing the first balloon to inflate so as to expand the stent to a desired degree;

(f) deflating the first balloon; and, (g) retracting the delivery system from the body vessel.

21. A system for delivery of a medical treatment device, comprising:

a) a balloon having distal and proximal ends, relative to the user; b) an elongated catheter having distal and proximal ends, on which the balloon is mounted ("balloon catheter") so the distal end of the balloon catheter protrudes therefrom; wherein the balloon catheter enclosed by the balloon is enlarged in diameter relative to the proximal end thereof; and, wherein further the balloon catheter has one or more lumens therethrough; c) a medical treatment device mounted onto the balloon; d) an insertion tip, having a proximal and a distal end, wherein the proximal end is carried on the balloon catheter proximate to the stent, and wherem the distal end tapers to form a tip.

22. A method for delivering a medical treatment device into a body vessel lumen, the device consisting of a stent, the method comprising:

(a) slidably disposing the delivery system of Claim 21 within a delivery catheter to enclose the stent within the delivery catheter, with the insertion tip protruding distally therefrom;

(b) inserting the delivery system and delivery catheter assembly formed in step (a) into a body vessel lumen;

(c) advancing the assembly into the lumen until the enclosed stent is in the desired position within the vessel;

(d) retracting the delivery catheter to expose the stent; (e) causing the balloon to inflate so as to expand the stent to a desired degree;

(f) deflating the balloon; and,

(g) retracting the delivery system from the body vessel.