Compliant blood vessel graft

Abstract

A graft for replacement of a section of an artery and methods of making the graft. The graft comprises a flexible, resilient, generally tubular external support and a blood vessel segment, e.g., a vein segment, carried within and having an ablumenal surface in contact with and supported by the tubular support, the graft being capable of resilient radial expansion in a manner mimicking the radial compliance properties of an artery.

Description

CROSS REFERENCE [0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10 / 834,360, filed Apr. 28, 2004, which claims priority from U.S. Provisional Application Ser. No. 60 / 466,226 filed Apr. 28, 2003, both of which applications are incorporated herein by reference in their entireties.FIELD OF THE INVENTION [0002] This invention involves a graft involving a blood vessel segment and a supportive sheath chosen to provide the graft with mechanical compliance properties which resemble those of a healthy native artery. BACKGROUND OF THE INVENTION [0003] Various types of vascular prostheses are known or available. Commercially available synthetic vascular grafts in use are commonly made from expanded polytetrafluoroethylene (e-PTFE), or woven, knitted, or velour design polyethylene terephthalate (PET) or Dacron®. These prosthetic vascular grafts may have various drawbacks. When used for repairing or replacing smaller diameter arteries, these grafts may fail d...

AI Technical Summary

Benefits of technology

[0007] It has now been found that a blood vessel segment such as a vein segment, if externally supported by an appropriate, flexible, radially-resiliently tubular support, can provide a valuable tubular prosthesis. A vein segment so supported can function in much the same fashion as the artery that is to be replaced. That is, it functions without undue bulging or aggravated mismatching phenomena leading to graft failure. Unless otherwise indicated, the term “compliance” means the ratio of the diameter change of a vessel as it expands in the radial direction in response to a given change in vessel pressure, and the values for compliance referred to below result from dynamic, in vitro testing. As described in greater detail below, the compliance of venous graft is largely dependent upon the compliance of the external, radially resilient support.

[0010] In other embodiments, the invention relates to a method for producing a venous graft for use, for example, in replacing a section of an artery. A segment of a vessel is provided, and is sheathed in a generally tubular support in supportive contact with the ablumenal surface of the vein segment. The support is sufficiently flexible and radially resilient as to provide the resulting graft with compliance properties mimicking the compliance properties of the artery to be replaced. Sheathing of the vessel segment within the tubular support may be accomplished by supporting the generally tubular support upon an exterior surface of an applicator having an internal passage within which is positioned the vessel segment, and removing the applicator to permit the tubular support to come into supportive contact with the ablumenal surface of the vessel segment. Axial dimensional changes in the tubular support may be controlled as necessary to provide the graft with the desired compliance properties mimicking arterial compliance properties.

Problems solved by technology

When used for repairing or replacing smaller diameter arteries, these grafts may fail due to occlusion by thrombosis or kinking, or due to an anastomotic or neointimal hyperplasia (exuberant cell growth at the interface between artery and graft).

Another problem may involve expansion and contraction mismatches between the host artery and the synthetic vascular prosthesis, which may result in anastomotic rupture, stimulated exuberant cell responses, and disturbed flow patterns and increased stresses leading to graft failure.

Problems also exist with the use of autologous saphenous vein grafts in these applications.

However, their success in the long term has been limited.

It is believed that these failures result from remodeling of the implanted vein in response to greatly increased internal pressure, that is, as the vein is required to function as an artery.

Veins, on the other hand, are not required to withstand arterial pressure variances and are relatively incapable of withstanding the higher arterial pressures without substantial bulging.

However, it appears that these reactions overcompensate in the veins, resulting in the phenomenon of neointimal hyperplasia yielding grossly thickened and stiff graft walls.

As the dilation of the vein segment continues, the resulting mismatch between the vein and artery diameters may lead to disturbance of flow patterns, which may also favor the formation of thrombi.

Problems also exist when tubular prostheses are used as exteriorly accessible shunts to facilitate access to the circulatory system for, e.g., the administration of medicines and nourishment and for dialysis procedures.

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