Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Including means for graft delivery
Reexamination Certificate
2001-12-04
2004-06-22
Ho, Tan-Uyen T. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Including means for graft delivery
C606S108000, C623S001110
Reexamination Certificate
active
06752827
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to medical devices, systems, and methods. More particularly, the present invention provides devices, systems, and methods for positioning an article, such as a graft or catheter, in a subcutaneous tunnel between skin and muscle tissue of a patient to establish improved access to the patient's vascular system for hemodialysis, hemofiltration, or other extracorporeal blood treatments.
Significant attention has been focused on the specific needs of vascular access for hemodialysis. Hemodialysis is generally the only treatment alternative for patients unable to receive a kidney transplant due to medical conditions, age, or absence of a donor. Hemodialysis, in part, takes up the excretory role of the kidney by drawing blood from the arterial system into a membrane separation device outside of the body, which transfers noxious substances from the blood into dialysate for disposal and returns the cleansed blood into the venous system of the patient. Hemodialysis and other extracorporeal treatment regimens that are repeated periodically, often for the lifetime of the patient, regularly utilize vascular grafts or catheters to improve blood flow characteristics. Vascular grafts, such as the Perma-Seal™ graft available from Possis Medical, Inc. and the VAG™ (venous arterial graft) available from Thoratec Laboratories Corporation, are permanently implanted in a subcutaneous tunnel, where one end of the graft is typically placed in an artery and the other end of the graft is typically placed in a vein so as to create an anastomosis between the two blood vessels. Access to the graft for hemodialysis is then achieved by percutaneous introduction of a needle or an access tube.
Recently, several graft designs have been proposed where the grafts are made of certain materials, such as polytetrafluoroethylene (PTFE), silicone, DACRON, polyurethane, bovine, and the like. These grafts are designed to offer immediate access to the patient's vasculature with reduced complications of hematomas between the subcutaneous tissue and the graft, kinking, thrombosis, pseudoaneurysm formation, or infection. While vascular grafts offer great promise, one issue to be resolved for the success and practical utility of vascular grafts is effective subcutaneous placement of such articles.
Subcutaneous placement of vascular grafts can be problematic since the grafts can easily be destroyed if they are stretched longitudinally as such forces change the graft's material properties. Previously proposed devices and methods for subcutaneously positioning a graft include attaching a graft directly onto a trailing end of a conventional tunneling tool which creates a subcutaneous path between two blood vessels. Such methods often result in significant longitudinal forces on the graft (as the graft is constantly being pulled behind the tunneler) which may potentially destroy the graft. Moreover, such protocols may result in twisting or kinking of the graft and a loose seal between the graft and the subcutaneous tissue as the tunnel created by the tunneler is typically of equal or larger diameter than the diameter of the vascular graft. A loose seal is undesirable as it makes it difficult to properly access the graft with a needle and increases the chances of hematomas, bleeding, and infection. Other proposed methods employ feeding a graft into a hollow tunneler or tube that is already positioned within the subcutaneous tunnel. Similarly, passing the graft into a hollow tube as well as removing the tube after the graft is positioned often results in significant longitudinal forces on the graft which compromise its structural integrity. In such instances, a loose seal is also created between the graft and the subcutaneous tissue as the diameter of the hollow tube will generally be greater than the diameter of the vascular graft to allow for release of the graft.
For these reasons, it would be desirable to provide devices, systems, and methods for positioning an article, such as a graft or catheter, in a subcutaneous tunnel between skin and muscle tissue of a patient to establish improved access to the patient's vascular system for hemodialysis, hemofiltration, or other extracorporeal blood treatments. In particular, it would be desirable if such devices, systems, and methods would minimize the friction or longitudinal forces acting against the vascular graft as it is being subcutaneously positioned. It would be further desirable if such devices, systems, and methods could provide a tighter seal between the graft and the subcutaneous tissue, minimize hematomas and infections, and enhance needle accessibility of the graft for extracorporeal treatment. The placement devices, systems, and methods should also allow for rotation of the graft without kinking or twisting complications. At least some of these objectives will be met by the devices, systems, and methods of the present invention described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 4,453,928 describes a catheter tunneling apparatus where a catheter is passed into a hollow tube which is already positioned within a subcutaneous tunnel by a conventional tunneler. U.S. Pat. No. 5,300,106 describes insertion and use of a tunneling tool. Vascular grafts are described in U.S. Pat. Nos. 4,409,172; 4,604,762; 4,675,361; 4,731,073; 4,861,830; 5,840,240; and 5,886,217. The full disclosures of each of the above references are incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
The present invention provides devices, systems, and methods for positioning an article, such as a graft or catheter, in a subcutaneous tunnel between skin and muscle tissue of a patient to establish improved access to the patient's vascular system, particularly peripheral blood vessels, for performing extracorporeal treatment on circulating blood. Exemplary extracorporeal treatment procedures include hemodialysis, hemofiltration, hemodiafiltration, plasmapheresis, apheresis, and the like. In particular, the present invention provides devices, systems, and methods which minimize longitudinal forces or friction acting against the vascular graft as it is being subcutaneously positioned while still providing a tight seal between the graft and the subcutaneous tissue, which in turn minimizes hematomas, bleeding, and infections and enhances needle accessibility of the graft for extracorporeal treatment. Moreover, the devices, systems, and methods of the present invention allow for rotation of the graft without kinking or twisting complications.
According to a first aspect of the present invention, a sheath for use with a tunneling tool comprises a pair of nested tubes and a coupling element. Each nested tube has a leading end, a trailing end, and a longitudinal opening or split. The coupling element is attached to the leading ends of the nested tubes and is removably attachable to a conventional tunneling tool. The nested tubes engage the catheter, graft, or other structure to be implanted. For example, by providing an inner tube with a diameter the same as or slightly smaller than the diameter or width of the article to be implanted, the article will be gripped by the inner tube. An outer tube may then be slid over the inner tube to apply a radially inward “clamping” force that enhances the inner tube grip. The longitudinal splits, however, allow the tubes to be easily opened to facilitate insertion of the articles being implanted. Once the article is inserted into the sheath, the article is passed into the subcutaneous tunnel with minimal distraction. Frictionless release of the article being implanted may then be effected by removing the sheath from over the article by separating the split nested tubes within the tunnel.
The nested tubes will usually have a uniform diameter along their entire length, typically being in the range from about 1 mm to 45 mm, preferably being in the range from 3 mm to 10 mm. The lengths of the nested tubes will usually be in the range fro
Ross John R.
Tobul James R.
Ho Tan-Uyen T.
Townsend and Townsend / and Crew LLP
Vasca, Inc.
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