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Interior liner for tubes, pipes, and blood conduits

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Interior liner for tubes, pipes, and blood conduits


A tube which circumferentially distends from its initial circumference upon the application of a circumferentially distending force such as applied by an internal pressure, and which exhibits minimal recoil following the removal of the circumferentially distending force. The tube preferably has a second circumference larger than the initial circumference which remains substantially unchanged by further increasing force once it has been achieved. Because of the distensible circumference and minimal recoil of the tube, the tube is useful as a liner for pipes and vessels and particularly for pipes and vessels having irregular internal surfaces to which the tube can smoothly conform. The tube is preferably made from porous PTFE with thin walls, in which form it is particularly useful as a liner for both living and prosthetic blood vessels and to line anastomoses between living and prosthetic blood vessels.

Inventors: Carey V. Campbell, Alvaro J. Laguna, James D. Lewis, Mark E. Mayrand, David J. Myers
USPTO Applicaton #: #20120310326 - Class: 623 113 (USPTO) - 12/06/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Arterial Prosthesis (i.e., Blood Vessel) >Stent In Combination With Graft

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The Patent Description & Claims data below is from USPTO Patent Application 20120310326, Interior liner for tubes, pipes, and blood conduits.

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RELATED APPLICATIONS

The present application is a Continuation of copending U.S. patent application Ser. No. 08/499,423 filed Jul. 7, 1995.

FIELD OF INVENTION

This invention relates to the field of interior liners for pipes and tubes and particularly to liners for blood conduits.

BACKGROUND OF THE INVENTION

There exists a need for a liner to provide a new interior surface lining for pipes and tubes in various applications. A liner having a smaller circumference than the inner circumference of the tube or pipe intended to be lined could be easily located axially within that pipe or tube. If such a liner were circumferentially distensible by the application of an internal pressure it could be expected to conform to the topography of the inner surface of the pipe or tube during use even if that surface were rough and irregular. Alternatively, an inflatable balloon could be used to circumferentially distend the liner to cause it to conform to the interior surfaces of the tube being lined. The ends of the liner could be affixed to the interior surface of the lined pipe or tube by various known mechanical fastening means; in some instances it may not require fastening, particularly at the downstream end. Such a liner would be of even greater utility if it were made from a highly chemically inert material.

Particularly useful applications of such a concept would be as an interior liner for prosthetic vascular grafts or natural vessels. For example, the liner could be installed within arteriovenous grafts cannulated by dialysis needles for kidney dialysis. Such grafts presently have a useful life expectancy often limited by the number of times they can be cannulated due to damage caused to the graft wall by the needles. Repeated cannulation in the same region results in fluid leakage through the graft. Once excessive leakage occurs, the graft is abandoned or bypassed. If it were possible to extend the life of the graft by providing it with a new interior lining surface, the graft could continue to be used for cannulation by dialysis needles and the patient would be spared the additional trauma and disfigurement resulting from implanting an entirely new graft. Such a liner may also inhibit tissue growth that often leads to unacceptable narrowing of the flow cross section. It might be useful for providing a smoother flow surface for anastomoses of vascular grafts or living blood vessels including graft-to-blood vessel anastomoses. The liner could also be used to provide additional strength to weak or damaged blood vessels or vascular grafts, or to intentionally occlude side tributaries in living blood vessels. Further, the inner surfaces of diseased vessels could be lined subsequent to enlarging the flow channel via balloon angioplasty, thrombectomy, or by other means.

Various published documents describe the use of porous PTFE vascular grafts as interior liners for blood conduits. See, for example, Marin M L et al., “Transluminally placed endovascular stented graft repair for arterial trauma,” J Vasc Surg 1994; 20:466-73; Parodi J C, “Endovascular repair of abdominal aortic aneurysms and other arterial lesions,” J Vasc Surg 1995; 21:549-57 and Dake M D et al., “Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms,” New England Journal of Medicine 1994; 331:1729-34. U.S. Pat. Nos. 5,122,154 to Rhodes and 5,123,917 to Lee describe similar applications. These documents typically describe the use of GORE-TEX□ Vascular Grafts or Impra□ Grafts as intraluminal grafts or interior liners for blood conduits. These commercially available porous PTFE vascular Grafts have specific disadvantages as interior liners.

GORE-TEX Vascular Grafts are porous PTFE tubes having a helical wrap of a reinforcing film that substantially prevents circumferential distension. The Impra Grafts do not have such a reinforcement and so may be circumferentially distended, however, these grafts will recoil significantly on release of the distending force and therefore must be retained in place by the use of mechanical means such as balloon expandable metal stents. Also as a result of the lack of a reinforcing layer, these grafts continue to circumferentially distend with exposure to increasing pressure and so do not have a second circumference at which the circumference stabilizes and does not substantially further distend with increasing pressure.

The disadvantages of presently available vascular graft materials for use as intraluminal grafts are well documented. For example, in a paper entitled “Endovascular Femoropopliteal Bypass: early Human Cadaver and Animal Studies” (Ann Vasc Surg 1995; 9:28-36), Doctor Ahn writes in describing the effectiveness of presently available intraluminal graft materials, “However, before this idea can be translated to broad clinical use, multiple problems still need to be resolved and/or avoided. The current study clearly shows the importance of a proper size match between the graft and the artery.” There is clearly a need for more effective intraluminal graft materials that are circumferentially distensible in order to conform smoothly to vessel walls without allowing retrograde dissection due to substantial recoiling of the graft following circumferential distension.

SUMMARY

OF THE INVENTION

The present invention is an interior liner for tubes, pipes and blood conduits comprising a tubular form circumferentially distensible and conformable whereby the first circumference of the interior liner (the initial circumference of the liner at zero pressure) may be distended by the application of pressure causing the first circumference to be increased to a larger circumference. The qualities of being circumferentially distensible under pressure and conformable allow the interior liner to be placed into another pipe or tube and be circumferentially distended under pressure until the interior liner is smoothly conforming without gross wrinkles to the interior surface of the other pipe or tube even if that surface represents a rough, irregular, damaged or otherwise non-uniform topography. The use of a porous polymer to construct the interior liner enhances its ability to conform.

For applications in which the pipe, tube, or blood conduit to be lined may not have adequate strength to resist expected normal fluid operating pressures, the interior liner of the present invention is preferably provided with a self-limiting circumference whereby it is circumferentially distensible up to a second circumference beyond which it will not substantially distend if used within the designed range of operating pressures. Pressures approaching the burst pressure of the interior liner are necessary to cause further substantial circumferential distension beyond the second circumference. The circumference can, however, be expected to grow in response to creep (time-dependent plastic deformation). This self-limiting feature is useful for lining weakened pipes, tubes or blood conduits whereby the liner itself is capable of withstanding the normal fluid operating pressure of the lined system.

Blood conduits include living blood vessels (veins and arteries) and vascular grafts of both prosthetic and natural materials. Vascular grafts of natural materials include, for example, materials of human umbilical components and materials of bovine origin.

In another embodiment, the interior liner of the present invention has minimal recoil after being circumferentially distended so that it remains proximate with all interior surfaces of the pipe, tube or blood conduit to which it has been fitted. Minimal recoil is considered to mean recoiling diametrically (or circumferentially) in an amount of 14 percent or less and more preferably 10 percent or less from a diameter to which the liner has been circumferentially distended by an amount of 25 percent, with the recoiled diameter measured 30 minutes following the release of the circumferentially distending force.

Particularly for applications relating to use as a liner for blood conduits, it is preferred that the interior liner have a second circumference beyond which it is not readily distensible and minimal recoil. For many of these applications, it may also be preferred that the liner have a wall thickness of 0.25 mm or less.

The term circumference is used herein to describe the external boundary of a transverse cross section of the article of the present invention. For any given amount of distension, the circumference is the same whether the article is wrinkled, folded or smooth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 describes a perspective view of the construction of an interior liner according to the present invention having a layer of helically-wrapped porous PTFE film applied in a single direction over the outer surface of a longitudinally extruded and expanded porous PTFE tube.

FIG. 2 describes a perspective view of the construction of an interior liner according to the present invention having two layers of helically-wrapped porous PTFE film applied in opposing directions over the outer surface of a longitudinally extruded and expanded porous PTFE tube.

FIG. 3 describes a perspective view of the construction of an interior liner according to the present invention having two layers of helically-wrapped porous PTFE film applied in opposing directions. No separate substrate porous PTFE tube is used beneath the film.

FIG. 4 shows a flow chart that describes a process for making a preferred interior liner of the present invention.

FIG. 5 describes an interior liner secured to a blood conduit by an expandable stent.



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Previous Patent Application:
Treatment of a main body lumen in the vicinity of a branching body lumen
Next Patent Application:
Non-foreshortening, axial tension constrainable stent
Industry Class:
Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
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stats Patent Info
Application #
US 20120310326 A1
Publish Date
12/06/2012
Document #
13590077
File Date
08/20/2012
USPTO Class
623/113
Other USPTO Classes
623/139
International Class
/
Drawings
5



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