Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
1998-09-17
2001-07-03
Prebilic, Paul B. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001130, C623S023720, C606S195000
Reexamination Certificate
active
06254627
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of expandable intraluminal support devices such as stents and the like. Typically, stents are expandable, tubular metallic devices that are positioned within a patient's vasculature or other body lumen and expanded in order to support a vessel or body lumen at a desired intraluminal location to allow the flow of blood or other body fluids therethrough. Often, the stents are formed from a deformable metal and delivered to the desired intraluminal location by mounting the stent onto an expandable portion, e.g. a balloon, on the distal extremity of a delivery catheter. By advancing the catheter through the body lumen, the stent may be delivered to a desired position and expanded therein by expanding the expandable member, e.g. the balloon to an expanded configuration, seating it within the artery or other body lumen. Other implementations make use of a self-expanding stent formed from a suitable material such as pseudoelastic material that is delivered in a constricted condition and when released spontaneously expands to an enlarged configuration. In other embodiments, a stent made of shape memory alloy (e.g. NiTi alloy) may be inserted into the body lumen in a martensitic phase and transformed to an austenite phase which has an expanded memory when raised to a temperature above the transformation temperature, usually less than 45° C.
Stents are often used in conjunction with an intravascular treatment for obstructive coronary artery disease. For example, ablation, atherectomy, balloon dilation, laser treatment or other procedures are among the method used to widen a stenotic region of a patient's vasculature. However, restenosis occurs in large percentage of percutaneous transluminal coronary angioplasty (PTCA) patients and rates can be even higher with other procedures. The prior art has employed a number of mechanical and pharmacological strategies to reduce the restenosis rate, but none have been particularly effective. Accordingly, stents have been proposed to maintain the patency of a treated vessel and prevent restenosis. Using stents, restenosis rates have fallen to less than 20%.
Restenosis is thought to be a natural healing reaction provoked by injury from the intravascular procedure. The healing process frequently causes thrombosis and may lead to intimal hyperplasia that occludes the vessel. Although helpful in reducing restenosis, stents do not represent a complete solution. The framework of the stent may still allow migration and proliferation of the smooth muscle cells, while the stent itself can be thrombogenic. To address these problems, stents have been covered with DACRON, PTFE and autologous vein and the stent surface has been seeded with endothelial cells or otherwise treated. Each of these solutions suffer from certain drawbacks, such as not being biocompatible, lacking sufficient mechanical strength, having a surface that is difficult to prepare, lack of ready availability and being thrombogenic. Antithrombotic drug regimens, in which anticoagulants and thrombolytic agents are administered during and after deployment of the stent, have also been employed to reduce the risk of thrombosis.
Thus, there remains a need for a stent capable of minimizing restenosis while having a consistency similar to the native artery, a non-thrombogenic surface and sufficient mechanical strength as well as being biocompatible and readily available. This invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The invention is directed to a stent assembly suitable for maintaining the patency of a bodily lumen, generally comprising an expandable stent and an expandable, biocompatible, non-thrombogenic jacket such as heterologous tissue disposed about the exterior of the expandable stent. Preferably, the heterologous tissue is selected from the group consisting of bovine pericardium, porcine pericardium, aortic leaflet and other suitable heterologous tissue. The stent may be an expandable, tubular framework and may be a conventional self expanding or balloon expandable stent. The jacket is disposed about either or both of the outer and inner surfaces of the stent. In a preferred embodiment, the jacket is generally cylindrical for corresponding to the tubular framework or the stent.
This invention is also directed to a method for maintaining the patency of a bodily lumen generally comprising providing a delivery catheter having an expandable member on the distal extremity thereof, mounting the stent assembly, including a tubular stent with a jacket of biocompatible, non-thrombogenic expandable material such as heterologous tissue disposed about at least part of the stent, on the expandable member on the distal extremity of the delivery catheter. The catheter is advanced through the body lumen within the patient until the distal extremity of the catheter having the stent assembly is positioned at a desired location therein. The stent assembly is expanded by expanding the expandable member onto which the stent assembly is mounted to anchor the stent assembly within the body lumen. Once the stent assembly is effectively positioned within the body lumen, the expanded expandable member may be contracted, e.g. by deflating the balloon, and then the delivery catheter may be withdrawn.
A presently preferred embodiment of the invention is directed to a stent assembly suitable for expansion within a body lumen and delivery of a therapeutic or diagnostic agent therein, generally comprising an expandable stent and an expandable, biocompatible, non-thrombogenic jacket such as heterologous tissue, which contains the therapeutic or diagnostic agent and which is disposed about the expandable stent. The jacket releasably contains at least one therapeutic or diagnostic agent.
A wide variety of therapeutic or diagnostic agents for a variety of indications can be used, including angiogenesis agents and antithrombotic agents. The term “antithrombotic agents” is meant to include various agents for reducing the risk of thrombosis, including anticoagulants such as heparin, thrombolytic agents such as urokinase, streptokinase, tissue plasminogen activator (ACTILYSE), monoclonal antibodies such as abciximab (REOPRO), fibrinolytic agents, and the like. Angiogenesis agents that stimulate the growth of neo-vessels include agents such as basic Fibroblast Growth Factor (bFGF) and Vascular Endothelial Growth Factor (VEGF).
In a presently preferred embodiment, the jacket is impregnated with a liquid containing the therapeutic or diagnostic agent. For example, a jacket formed from heterologous tissue which is submerged in a solution of the therapeutic agent will absorb the solution. A variety of suitable methods of applying the agent to the jacket may be used, including using electrodeposition, heat and pressure. Thereafter, the stent assembly can be positioned at a desired site within the patient's body lumen, where the jacket will release the therapeutic agent. The jacket on the stent assembly may be impregnated just before use, or alternatively, stored in the therapeutic or diagnostic agent so that the stent assembly is preimpregnated.
The invention is also directed to a method for delivery of a therapeutic or diagnostic agent within a body lumen. The stent assembly including a tubular stent with a jacket of biocompatible, non-thrombogenic expandable material, such as heterologous tissue, containing a therapeutic or diagnostic agent is positioned within the body lumen as outlined above. With the stent assembly positioned at a desired location, the therapeutic or diagnostic agent is released from the jacket into the body lumen and thereby delivered at and around the location of the stent assembly within the body lumen.
The expanded jacket of biocompatible, non-thrombogenic expandable material such as heterologous tissue should extend over a substantial portion, preferably all, of the stenotic region in which it is disposed in order to minimize the restenosis.
REFERENCES:
patent: 4400833 (1983-08-01), Kurland
patent: 45021
Diseno y Desarrollo Medico S.A. de C.V.
Heller Ehrman White & McAuliffe LLP
Prebilic Paul B.
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