Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
1998-07-22
2001-05-22
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001110
Reexamination Certificate
active
06235051
ABSTRACT:
This invention pertains to medical devices and procedures and, more particularly, to improved stent grafts and methods of deployment thereof. The invention has application in the repair of vasculature, such as aneurysms of the abdominal aorta.
Aneurysms of the abdominal aorta, defined as enlargement to greater than 1.5 times the normal diameter, occur in 36 per 100,000 individuals annually, with an overall prevalence of 6% of men by the age of 80, and 4.5% of women by the age of 90. Rupture of an abdominal aortic aneurysm is associated with up to a 62% death rate prior to reaching a hospital, and with a death rate over 50% for those who reach the hospital for emergency surgery. Aneurysm rupture is related to size; the 5-year incidence of rupture of 4 to 5 cm abdominal aortic aneurysms range from 3 to 12 percent, whereas the 5-year risk of rupture of aneurysms greater than 5 cm diameter ranges from 25% to 41%. Two series of patients with abdominal aortic aneurysms followed without treatment in the 1950's demonstrated 5-year survival of 4% and 19%. Subsequent series have demonstrated 5-year survival of 49% to 84% in patients who undergo elective surgery for abdominal aortic aneurysm.
Surgical treatment of abdominal aortic aneurysms has been the standard therapy since its introduction in 1951. Replacement of an aneurysm with a prosthetic graft is the current standard therapy, but elective surgery is associated with a 5% death rate in low-risk patients, 20% major complication rate, lengthy hospitalization, and significant cost. Additionally, many patients have comorbid conditions that preclude elective surgery, such as heart disease or chronic lung disease.
In 1991, Dr. Juan Parodi described a method of aneurysm repair that involved placement of an intraluminal aortic graft through an excision in the femoral artery, averting the risk and expense of major abdominal surgery through a midline or flank incision. The method involved surgical exposure of the common femoral artery in the upper thigh, and placement of an 22 French (8 mm outer diameter) introducer through the femoral artery, iliac artery, and into the aorta. Through this introducer, a prosthetic tube graft attached at both ends to a self-expanding intravascular stent were passed into the aorta. After positioning using fluoroscopic x-ray guidance, the introducer is retracted, and the stents dilated using balloon angioplasty. The stents served to anchor the graft in the aorta.
Although successful at excluding aneurysms limited to the abdominal aorta, the majority (80%) of aneurysmal abdominal aortas are dilated to the termination of the aorta, or extend into one or both iliac arteries. For such patients, placement of a simple “tube” graft in the aorta is not sufficient to prevent subsequent aneurysm expansion or rupture.
Patients with aortic aneurysms that extend to the aortic termination or into the iliac arteries require placement of a “bifurcated” graft, or an aortic Y-graft. The placement of a bifurcated stent-graft into the aorta through a common femoral arteriotomy poses many technical challenges. First, introducer sheaths must be sizable, ranging from 24 to 30 French (inner diameter, or 9 to 11 mm diameter outer diameter). Placement of the contralateral iliac limb requires snaring or retrieval of the limb via a catheter placed in the contralateral femoral artery, or reassemble of a bifurcated graft in the body from components. Usually, components include an aortic limb and a single iliac limb placed through one femoral artery, and a second iliac limb placed through the other femoral artery in the opposite leg. This system requires engagement of an opening in the aortic segment with the iliac segment after introduction and deployment of the aortic segment in the aorta.
Disadvantages of these methods include being cumbersome, and the potential for leakage of blood into the aneurysm sac through the junction of the components due to inadequate seal after placement or due to subsequent disjunction. They have the disadvantage of requiring surgical access of one or both femoral arteries for placement. Additionally, many patients do not have iliac arteries of sufficient size to allow placement of large introducer sheaths through them into the aorta. This may prevent the performance of the procedure, or may result in complications in the iliac arteries such as dissection, rupture, or transection.
In view of the foregoing, an object of this invention is to provide improved stent-grafts and methods of deployment thereof. A more particular object is to provide improved stent-grafts and methods for use in repair of vascular cavities, such as aneurysms of the abdominal aorta.
A related object of the invention is to provide improved such stent-grafts and methods as permit the repair of aneurysmal abdominal aortas that are dilated to the termination of the aorta or that extend into the iliac arteries.
A further related object of the invention is to provide improved such stent-grafts and methods as overcome the complications associated with the deployment of conventional stent- grafts.
Still another object of the invention is to provide stent-grafts that can be fabricated from existing materials and without the use of complicated manufacturing technologies and, hence, that can be produced at low cost and with high quality.
Yet still another object of the invention is to provide stent-grafts that can be emplaced without complicated and time-consuming surgical techniques.
SUMMARY OF THE INVENTION
The aforementioned objects are among those achieved by the invention, one aspect of which provides a vascular stent-graft system, comprising a stent-graft with an expandable tip and a restraining member disposed about at least a portion of that tip. The restraining member constrains expansion of the tip, even absent contact with a delivery device by which the stent-graft is deployed. Unlike prior art designs, the tip can be partially positioned and at least temporarily freed from the grasp of a deployment device without risk that the tip will be prematurely expand into a potentially undesirable fit in the aorta.
The stent-graft can be of any desirable configuration having at least one expandable tip. Typical configurations are tubular (with two such tips) or Y-shaped (with three such tips), each for placement at a respective end of the vascular region to be repaired. Though the tips are typically not tapered when in their expanded states, the distal ends of the restraining member can be. This facilitates moving the member and the tip it encases within the vasculature or removing the restraining member from the vasculature after deployment.
According to further aspects of the invention, the restraining member is a sleeve of fabric or web. In other aspects, the restraining member comprises a wrap, e.g., of suture or other thread-like material. In either event, the member preferably comprises a biocompatible material such as polyethylene, polytetraflouroethylene, polypropylene, nylon, or silk.
The restraining member, according to further aspects of the invention, can be detachably affixed, e.g., by way of a suture loop, a hook, an aperture, a button, a hook-and-loop, or interference or friction fit. This degree of affixation can be great enough to permit the tip or stent-graft to be positioned by grasping and pulling of the member, but not so great as to prevent the restraining member from being deliberately pulled off the tip, e.g., via a deliberate tug.
A related aspect of the invention provides a stent-graft system as described above where the restraining member is removed from the tip via motion in a central-to-peripheral direction, that is, motion in a direction away from a central portion of the stent graft and towards a peripheral portion of the tip. A sleeve-like restraining member that is slidably removable, for example, can be slid away from the central portion (or body) of the stent-graft and pulled off the tip. In the case of a thread-like restraining member that is wrapped around the tip (e.g., a suture wrap), a free end of the
Nutter & McClennen & Fish LLP
Powsner David J.
Smith Jeffrey A.
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