Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent in combination with graft
Reexamination Certificate
1998-08-14
2002-05-28
Recla, Henry J. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent in combination with graft
C606S198000, C623S001360
Reexamination Certificate
active
06395019
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a system and method for the treatment of disorders of the vasculature. More specifically, the present invention relates to a system and method for treatment of abdominal aortic aneurysm and the like, which is a condition manifested by expansion and weakening of the aorta below the diaphragm. Such conditions require Intervention due to the severity of the sequelae, which frequently is death. Prior methods of treating aortic aneurysm have consisted of invasive surgical methods with graft placement within the aorta as a reinforcing member of the artery. However, such a procedure requires a surgical cut down to access the vessel, which in turn can result in a catastrophic rupture of the aneurysm due to the decreased external pressure from the organs and tissues surrounding the aorta, which are moved during the procedure to gain access to the vessel. Accordingly, surgical procedures have a high mortality rate due to the possibility of the rupture discussed above in addition to other factors. Such other factors can include poor physical condition of the patient due to blood loss, anuria, and low blood pressure associated with the aortic abdominal aneurysm. An example of a surgical procedure is described in a book entitled
Surgical Treatment of Aortic Aneurysms
by Denton A. Cooley, M.D., published in 1986 by W. B. Saunders Company.
Due to the inherent risks and complexities of surgical procedures, various attempts have been made In the development of alternative methods for deployment of grafts within aortic aneurysms. One such method is the non-invasive technique of percutaneous delivery by a catheter-based system. Such a method is described in Lawrence, Jr. et al in “Percutaneous Endovascular Graft: Experimental Evaluation”,
Radiology
(May 1987). Lawrence described therein the use of a Gianturco stent as disclosed in U.S. Pat. No. 4,580,568. The stent is used to position a Dacron fabric graft within the vessel. The Dacron graft is compressed within the catheter and then deployed within the vessel to be treated. A similar procedure has also been described by Mirich et at in “Percutaneously Placed Endovascular Grafts for Aortic Aneurysms: Feasibility Study”,
Radiology
(March 1989). Mirich describes therein a self-expanding metallic structure covered by a nylon fabric, with said structure being anchored by barbs at the proximal and distal ends.
One of the primary deficiencies of the existing percutaneous devices and methods has been that the grafts and the delivery catheters used to deliver the grafts are relatively large in profile, often up to 24 French and greater, and stiff in bending. The large profile and bending stiffness makes delivery through the irregular and tortuous arteries of diseased vessels difficult and risky. In particular. the iliac arteries are often too narrow or irregular for the passage of a percutaneous device. Because of this, non-invasive percutaneous graft delivery for treatment of aortic aneurysm is not available to many patients who would otherwise benefit from it.
Another contraindication for current percutaneous grafting methods and devices is a vessel treatment site with high neck angulation which precludes a proper fit between the graft and the vessel wall. An improper fit or seal between the graft and the vessel wall can result in leaks or areas of high stress imposed upon the diseased vessel which lead to reduced graft efficacy and possibly rupture of the aneurysm.
While the above methods have shown some promise with regard to treating abdominal aortic aneurysms with non-invasive methods, there remains a need for an endovascular graft system which can be deployed percutaneously in a small diameter flexible catheter system. In addition, there is a need for a graft which conforms more closely to the contours of an aortic aneurysm which are often quite irregular and angulated and vary from patient to patient. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed generally to an endovascular graft for vascular treatment and a method for manufacturing and using the graft. The graft generally has an inflatable tubular frame structure which can be configured to conform to the morphology of a patient's vessel to be treated. The frame structure has a proximal end and a distal end with an inflatable cuff disposed on at least one end and preferably both. The inflatable cuffs can-be reduced in diameter and profile when deflated for introduction into a patient's vasculature by a catheter based delivery system or other suitable means. The inflatable cuffs provide a sufficiently rigid structure when inflated which supports the graft and seals the graft against the interior surface of the vessel in which it is being deployed. One or more elongated inflatable channels may also be disposed on the graft. Preferably, the elongated channel is disposed between and in fluid communication with a proximal and distal inflatable cuff. The channel provides the desired stiffness upon inflation, prevents kinking of the graft frame, and facilitates deployment of the graft within a patient's body passageway. The elongated inflatable channel can be in a longitudinal or linear configuration with respect to the graft, but is preferably shaped as a helix disposed about the graft. Other orientations such as interconnecting grids or rings may also be suitable for the elongated channels. The inflatable cuffs and the elongated channel contain fluid tight chambers which are generally in fluid communication with each other but which may also be separated by valves or rupture discs therein to selectively control the sequence of inflation or deployment. The fluid tight chambers are typically accessed by an injection port which is configured to accept a pressurized source of gas, fluid, particles, gel or combination thereof and which is in fluid communication with at least one of the fluid tight chambers. A fluid which sets, hardens or gels over time can also be used. The number of elongated channels can vary with the specific configuration of the graft as adapted to a given indication, but generally, the number of channels ranges from 1 to 25, preferably 2 to about 8.
A proximal neck portion may be secured to the proximal inflatable cuff. The proximal neck portion has a flexible tubular structure that has a diameter similar to the proximal inflatable cuff. The proximal neck portion can be configured as a straight tubular section or can be tapered distally or proximally to an increased or decreased diameter. Preferably, the proximal neck portion is secured and sealed to the proximal inflatable cuff and tapers proximally to an increased diameter so as to engage the inside surface of a vessel wall which provides a sealing function in addition to that of the proximal inflatable cuff. Such a configuration also smoothes the transition for fluid flow from the vessel of a patient to the lumen or channel within the endovascular graft. The proximal neck portion has an inlet axis that preferably has an angular bias with respect to a longitudinal axis of the graft.
Preferably, the graft has a monolithic structure wherein the material that comprises the inflatable cuffs and channels extends between these elements in a thin flexible layer that defines a longitudinal lumen to confine a flow of blood or other fluid therethrough. Such a monolithic structure can be made from a variety of suitable polymers including PVC, polyurethane, polyethylene and fluoropolymers such as TFE, PTFE and ePTFE. Additional stiffness or reinforcement can be added to the graft by the addition of metal or plastic inserts or battens to the graft, which can also facilitate positioning and deployment of the graft prior to inflation of an inflatable portion of the graft.
In another embodiment, the graft has a thin flexible layer disposed over or between a proximal inflatable cuff, a distal inflatable cuff, and an elongated inflatable channel of the frame. The thin flexible layer is made of a mate
Heller Ehrman White & McAuliffe LLP
Lewis William W.
Recla Henry J.
TriVascular Inc.
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