Tubular graft with monofilament fibers

Details Tubular graft with monofilament fibers Tubular graft with monofilament fibers

1999-09-27

2002-02-05

Recla, Henry J. (Department: 3731)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Arterial prosthesis

C623S001350, C623S001330, C623S001250

Reexamination Certificate

active

06344052

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to tubular prostheses such as grafts and endoluminal prostheses including, for example, stent-grafts and aneurysm exclusion devices, and methods for placement of such grafts and endoluminal structures. More particularly, the present invention relates to a graft or a prosthetic device including a graft constructed of monofilament fibers for placement within or in place of a body lumen, including, for example, vascular grafts for replacing blood vessels, devices for opening or supporting blood vessels, and devices for the treatment of abdominal and other aneurysms.
BACKGROUND OF THE INVENTION
A wide range of medical treatments have been previously developed using “endoluminal prostheses,” which terms are herein intended to mean medical devices which are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring or artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed, each providing a uniquely beneficial structure to modify the mechanics of the targeted luminal wall.
Also a number of vascular grafts have been developed for either replacing, supplementing or excluding portions of blood vessels. These vascular grafts may include but are not limited to endoluminal vascular prostheses.
Graft materials have been used in a number of medical applications including in vascular graft and/or in endoluminal prostheses. Among other applications, materials have been used in tubular vascular prostheses for repairing or replacing blood vessels. They have also been used in aneurysm exclusion devices such as abdominal aortic aneurysm (“AAA”) devices that are used to exclude aneurysms and provide a prosthetic lumen for the flow of blood. Further uses have included stent-grafts such as covered stents that are used for providing artificial radial support to the wall tissue, which forms the various lumens in the body. Such covered stents have attempted among other things to address problems that are presented by a thrombogenic environment or to promote healing in the vessel wall tissue that is prone to scarring. These attempts include providing a lining or covering in conjunction with an implanted stent. Typically graft materials used in these include multifilament woven polymer materials and polytetrafluoroethylene (“PTFE”). The stent-grafts may have graft material on the inner diameter or outer diameter of a support structure.
One very significant of these uses for endoluminal or vascular grafts is in treating aneurysms.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease or genetic predisposition which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aneurysms occurring in the abdominal aorta. Typically an abdominal aneurysm will begin below the renal arteries and may extend into one or both of the iliac arteries.
Aneurysms, especially abdominal aortic aneurysms, have been most commonly treated in open surgery procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique in view of the alternative of a fatal ruptured abdominal aortic aneurysm, the open surgical technique suffers from a number of disadvantages. The surgical procedure is complex and requires long hospital stays due to serious complications and long recovery times and has high mortality rates.
In order to reduce the mortality rates, complications and duration of hospital stays, less invasive devices and techniques have been developed. The improved devices include tubular prostheses that provide a lumen or lumens for blood flow while excluding blood flow to the aneurysm site. The prostheses are typically made of a tubular multifilament woven graft material that is secured to a vessel wall above and below the aneurysm site with at least one attached expandable ring member that provides sufficient radial force so that the prosthesis engages the inner lumen wall of the body lumen. Other mechanisms have been used to engage the vessel walls such as, for example, forcibly expandable members or hook like members that puncture the vessel wall.
Although frequently referred to as stent-grafts, these devices differ from covered stents in that they are not used to mechanically prop open natural blood vessels. Rather, they are used to secure an artificial lumen to the vessel wall without further opening the natural blood vessel that is already abnormally dilated.
These aneurysm exclusion devices are preferably loaded into a catheter, which is used to deliver and place the prosthesis at an appropriate location. This has been done one of several ways. Most frequently, a surgical cut down is made to access a femoral iliac artery. The catheter is then inserted into the artery and guided to the aneurysm site using fluoroscopic imaging where the device is released from the catheter. Where expandable rings are used, the rings supporting the graft, biased in a radially outward direction, then expand to engage the prosthesis in the vessel against the vessel wall to provide an artificial lumen for the flow of blood. Another technique, though less frequently used, includes percutaneously accessing the blood vessel for catheter delivery, i.e., without a surgical cutdown.
Multifilament fibers have been used in AAA devices, primarily because it was believed that the fibers provide relative strength and durability required by the prostheses and monofilament fiber based grafts have been avoided because they had insufficient leak resistance. Typically the woven multifilament graft material is made of yarns which consist of about 25 to 100 fibers. The selection of yarn dictates the resultant mechanical properties such as percent elongation, fatigue strength, burst strength, and permeability to water or other fluids. One disadvantage to using these materials is that the multifilament fiber adds bulk, and relatively bulky grafts are more difficult to deliver using modem low-profile endovascular techniques. Another disadvantage is that they cannot be woven into fabric without a significant number of fissures or hooks (frays) and defects that occur during the weaving process. These fissures, hooks and defects tend to make the woven graft material even thicker and may cause increased tissue immune response. Lower profile multifilament woven materials have not provided sufficient strength to the grafts in which they have been used.
One disadvantage of the currently used devices is that when radially compressed, they are larger than would be ideal and thus require larger diameter catheters for delivery. This makes catheter access to the site and maneuverability through the tortuous or narrowed diseased vessels more difficult and may exclude some patients from eligibility for some procedures. In most current AAA devices, the total outer diameter of the introducer systems are relatively large, i.e., around 20-24 French. Providing a smaller introducer system would, among other things, allow for treatment of patients with smaller blood vessel diameters and provides for faster delivery.
Therefore, it is desirable to provide an endoluminal graft that is made of a material having sufficient strength, durability and low-permeability, while capable of being radially compressed into and delivered from smaller diameter delivery catheters.
SUMMARY OF THE INVENTION
The present invention provides an improved endoluminal prosthesis made of a graft material having a relatively smaller collapsed profile. In particular, the present invention provides an endoluminal graft device made of monofilament f

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