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Arteriovenous access valve system and process

Arteriovenous access valve system and process description/claims

The present application is a continuation-in-part of U.S. patent application Ser. No. 11/807,479, filed May 29, 2007.

The function of kidneys, which are glandular organs located in the upper abdominal cavity of vertebrates, is to filter blood and remove waste products. Specifically, kidneys separate water and waste products of metabolism from blood and excrete them as urine through the bladder. Chronic renal failure is a disease of the kidney in which the kidney function breaks down and is no longer able to filter blood and remove waste substances. Should certain toxic waste substances not be removed from the blood, the toxic substances may increase to lethal concentrations within the body.

Hemodialysis is a life-sustaining treatment for patients who have renal failure. Hemodialysis is a process whereby the patient's blood is filtered and toxins are removed using an extracorporeal dialysis machine. For hemodialysis to be effective, large volumes of blood must be removed rapidly from the patient's body, passed through the dialysis machine, and returned to the patient. A number of operations have been developed to provide access to the circulation system of a patient such that patients may be connected to the dialysis machine.

For example, the most commonly performed hemodialysis access operation is a subcutaneous placement of an arteriovenous graft, which is made from a biocompatible tube. The biocompatible tube can be made of, for instance, a fluoropolymer such as polytetrafluoroethylene. One end of the tube is connected to an artery while the other end is connected to a vein. The arteriovenous graft is typically placed either in the leg or arm of a patient.

Blood flows from the artery, through the graft and into the vein. To connect the patient to a dialysis machine, two large hypodermic needles are inserted through the skin and into the graft. Blood is removed from the patient through one needle, circulated through the dialysis machine, and returned to the patient through the second needle. Typically, patients undergo hemodialysis approximately four hours a day, three days a week.

Various problems, however, have been experienced with the use of an arteriovenous graft. For example, arterial steal occurs when excessive blood flow through the arteriovenous graft “steals” blood from the distal arterial bed. Arterial steal can prevent the proper supply of blood from reaching the extremity of a patient.

Various other complications can also occur. For instance, the blood flowing through the arteriovenous graft can often reach turbulent flow rates. This stream of fast moving blood then exits the arteriovenous graft and contacts the vein connected to the graft. This collision between the flow of blood and the vein may cause the development of myointimal hyperplasia which leads to the thickening of the vein walls and a narrowing of the vessel. As the vein narrows, flow through the arteriovenous graft decreases and blood within the graft may ultimately clot.

The cessation of blood flow through the graft caused by clot formation is known as graft thrombosis. Numerous techniques and medications have been studied in attempts to block the development of the scar tissue. Graft thrombosis, however, continues to remain a reoccurring complication associated with the use of arteriovenous grafts.

In view of the above drawbacks, a need currently exists in the art for an arteriovenous graft that can prevent and minimize arterial steal and graft thrombosis. A process for using an arteriovenous graft in minimizing arterial steal and graft thrombosis is also needed.

In general, the present invention is directed to subcutaneous arteriovenous graft systems and to processes for using the arteriovenous graft systems in a manner that eliminates or at least reduces arterial steal and graft thrombosis. In one embodiment, for instance, the system includes an arteriovenous graft having an arterial end and an opposite venous end. The arterial end is configured to be connected to an artery to form an arterial anastomosis, while the venous end is configured to be connected to a vein to form a venous anastomosis.

In accordance with the present invention, the system includes at least one valve device positioned at the arterial end of the arteriovenous graft. In one embodiment, for instance, the valve device comprises an inflatable balloon. The inflatable balloon is positioned so as to restrict blood flow through the arteriovenous graft when inflated. In general, the valve device should be positioned at the arterial end of the arteriovenous graft as close as possible to the intersection of the graft with an artery. For example, the valve device may be positioned so as to restrict blood flow through the arteriovenous graft at a location that is less than about 10 mm from the intersection of the arteriovenous graft and an artery.

The inflatable balloon of the valve device may have an annular shape that surrounds the arteriovenous graft. The inflatable balloon may also be a separate structure or may be integral with the arteriovenous graft. When integral with the arteriovenous graft, the arteriovenous graft may include a multi-layered segment located at the arterial end. The multi-layered segment may comprise an inner layer and an outer layer. The inner layer constricts the graft when a fluid is fed in between the inner layer and the outer layer. When having an annular shape, the balloon may be surrounded by a rigid collar that serves to assist the balloon in constricting the graft.

In an alternative embodiment, the valve device may include an inner sleeve and an outer sleeve. The inner sleeve may be attached to the outer sleeve except for over a discrete area. The discrete area can be in fluid communication with a fluid delivery device. When a fluid is fed to the discrete area, fluid is fed in between the inner sleeve and the outer sleeve causing the discrete area of the inner sleeve to inflate. In this embodiment, the discrete area, instead of surrounding the arteriovenous graft, can be circular or substantially circular in shape. When inflated, the discrete area forms a spherically shaped or a substantially spherically shaped balloon. In one embodiment, for instance, the outer sleeve may be more rigid than the inner sleeve. Thus, when the inner sleeve is inflated, the outer sleeve maintains its shape. In this embodiment, the balloon may be integral with the arteriovenous graft. Alternatively, the arteriovenous graft may be positioned within the inner sleeve.

In order to inflate and deflate the balloon, in one embodiment, the valve device can further include an injection port in fluid communication with the inflatable balloon. The injection port defines a diaphragm configured to receive a hypodermic needle for injecting fluid into or withdrawing fluid from the balloon. Of particular advantage, the injection port may also be subcutaneously implanted.

In an alternative embodiment, the inflatable balloon may be positioned in operative association with a piston. In this embodiment, when the balloon is inflated, the balloon forces the piston either towards or away from the arteriovenous graft for opening or closing the valve device.

When the valve device contains a piston, the valve device can include various configurations. Further, the piston can be used to inflate a balloon as described above or can be used to activate any other suitable structure configured to open and close the arteriovenous graft. In fact, in one embodiment, the piston itself may be used to open and close the graft.

In one embodiment, for example, the valve device may comprise a magnetically activated piston. In this embodiment, when a magnetic field is placed in close proximity to the valve device, the piston is moved for either opening or closing the valve device. For example, in one embodiment, placing a magnetic field in close proximity to the valve device opens the device which normally remains closed.

In one particular embodiment, the magnetically activated piston may be activated when exposed to a changing magnetic field, such as a pulsing magnetic field. In this embodiment, the valve device may include a coil member configured to convert a changing magnetic field into an electric current. The coil member is in communication with a solenoid. The solenoid is configured to move the piston and open or close the valve device when electric current is received from the coil member.

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• Utility Patent

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