Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Having plural layers
Reexamination Certificate
1998-11-25
2001-12-18
Milano, Michael J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Having plural layers
C623S001210
Reexamination Certificate
active
06331191
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 thoracic or abdominal aortic aneurysm and the like, which is a condition manifested by expansion and weakening of the aorta. Such conditions require intervention due to the severity of the sequelae, which frequently is death. Prior methods of treating aneurysms have consisted of invasive surgical methods with graft placement within the affected vessel 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 surrounding organs and tissues, 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 Aneurvsms
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 al. in “Percutaneously Placed Endovascular Grafts for Aortic Aneurysms: Feasability 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. In addition, current devices are particularly challenged to reach the deployment sizes and diameters required for treatment of lesions in the aorto and aorto-iliac regions. 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.
While the above methods have shown some promise with regard to treating thoracic and 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. The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed generally to a system and method for treatment of a body lumen or passageway within a patient's body. More specifically, the invention is directed to an endovascular graft for treatment of weakened or diseased blood vessels which has at least two thin wall graft members which are configured to be nested or layered over each other in a deployed state. By layering a plurality of thin wall graft members, each layer can be delivered by a smaller more flexible catheter delivery system than is used for conventional single graft systems. The system of the present invention may delivered intraoperatively, but is preferably delivered percutaneously.
One embodiment of the invention is a graft for supporting a preselected length of a patient's body lumen or passageway that is created from at least two separate thin wall graft members. The thin wall graft members are configured to be nested or layered when deployed in an overlapping fashion that combines the strength of the members in the areas or portions that are overlapped. One advantage of such a system and method is that each individual thin wall graft member can be constructed with less bulk and material mass than would be required for a single component graft of similar strength. This allows each separate thin wall graft member to have a smaller more flexible profile in a compressed or constricted state and be deliverable through a smaller and more flexible delivery system which improves access to preselected lengths of compromised or diseased body lumens.
The graft can be configured so that no single component or thin wall graft member has sufficient mechanical strength to provide a desired amount of support for a preselected length of a patient's body lumen. The thin wall graft members can be designed so that a desired amount of mechanical strength can be achieved with two or more layers or overlapped portions of the graft. In some indications, it may be desirable to have three, four, five or more layers required to achieve the desired amount of mechanical strength and support for the patient's body lumen. While a graft requiring more layers for sufficient strength may be more time consuming to deploy, each thin wall graft member or component can be made correspondingly thinner and with a lower more flexible profile in a constrained or compressed state. This allows a correspondingly smaller and more flexible catheter delivery system to be used to access the preselected length of body lumen to be treated.
In some embodiments, it may be preferable to have the inner-most and lastly deployed thin wall graft member be of a longitudinal length greater than the previously deployed thin wall graft members, individually, or cumulatively as deployed. In this way, the lastly deployed thin wall graft member can extend longitudinally from one or both ends of the graft and provide a smooth transition into the graft for blood flow and a smooth inner surface for the graft in its final deployed state.
Generally it is desirable for the preselected length of a patient's body lumen which is compromised or requires treatment to be completely spanned by at least the number of thin wall graft members required to achieve a desired amount of mechanical strength and support. In this way, each thin wall graft member that provides a portion of the requisite desired strength can be anchored with appropriate anchoring mechanisms in tissue that is healthy or of sufficient integrity to be capable of supporting the anchoring mechanisms. Each thin wall graft member is typically equipped with at least one anchoring mechanism at each end to prevent the thin wall graft member from being displaced from the deployment site and to facilitate sealing of the graft member against an inside surface of the patient's body lumen or vessel.
In an alternative embodiment of a graft of the present invention, thin wall graft members are linked to allow relative longitudinal movement or displacement of the members. In a preferred embodiment, each thin wall graft member is connected to an adjacent member in a telescopic manner. This allows the graft members to be extended longitudinally so that only one thickness of graft member need be compressed or constrained for loading of the graft into a delivery catheter system, except for the short lengths of overlapped portion where the ends of the thin wall graft members are joined. This provides some of the advantages o
Anderson William B.
Heller Ehrman White & McAuliffe
Milano Michael J.
TriVascular Inc.
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