Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent in combination with graft
Utility Patent
2000-02-16
2001-01-02
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent in combination with graft
Utility Patent
active
06168620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to devices and methods for endovascular treatment of blood vessel anomalies and, more particularly, for the implantation of vascular grafts.
2. Description of the Prior Art
Blood vessel anomalies, such as aneurysms, stenoses, etc., have been treated in the prior art through surgical procedures, wherein the diseased portion of the blood vessel may be ablated and replaced with a, prosthetic member, such as shown in U.S. Pat. No. 4,938,740 to Melbin. An improvement over this technique which obviates the need for open surgery is directed to the endovascular placement of a stent-reinforced graft. The stent and graft is entered into the bloodstream from a remote puncture site, typically through the neck or femoral region, via a catheter in an unexpanded state to facilitate movement thereof through the blood vessel. The stent/graft assembly is aligned in the blood vessel using techniques known by those skilled in the art such that the assembly extends between healthy portions of the blood vessel and by-passes the blood vessel anomaly. Once properly aligned, the stent and graft are caused to expand thereby engaging axially-spaced sections of healthy blood vessel wall and defining an enclosed pathway for blood flow through the anomaly. If, for example, a graft was disposed in such a manner to by-pass an aneurysm and such aneurysm ruptured, the emplaced graft would act as a conduit to maintain a continuous flow of blood through the ruptured portion of blood vessel.
Different devices are in the prior art which allow for endovascular movement of a stent and/or graft and expansion thereof. First, devices exist adapted to selectively elongate and foreshorten a length of tubular graft material, resulting in a corresponding change in diameter of the graft, such as in U.S. Pat. No. 5,464,449 to Ryan et al. Alternatively, a stent and/or graft may be directly disposed on an expandable angioplasty balloon, as shown in U.S. Pat. No. 5,554,182 to Dinh et al. Finally, self-expanding stents and/or grafts are known in the prior art which are spring-biased or formed of temperature sensitive material. An example of this third type of prior art is found in U.S. Pat. No. 5,562,725 to Schmitt et al.
The prior art, however, has some deficiency in providing for implantation of a stent-reinforced graft. The mounting of the graft onto a stent, in addition to a control mechanism or an angioplasty balloon, results in the graft defining a relatively significant outer dimension. As is readily appreciated, due to the small dimensions of blood vessel lumens, it is desirable to keep the profile of all endovascular devices to a minimum. Also, lower profile instruments are more easily manipulated through blood vessels, than larger profile instruments especially through blood vessels which may contain accumulated plaque.
It is an object of the subject invention to provide a collapsible support for a vascular graft which allows for low-profile insertion thereof.
It is also an object of the subject application to provide a support for maintaining a graft in a semi-expanded state with sufficient space within the graft to preferably accommodate an unexpanded stent.
SUMMARY OF THE INVENTION
The aforementioned objects are met by a frame for supporting a vascular graft. In a first embodiment, the frame is formed from two flexible angiographic guidewires bent to define two spaced-apart loops, the loops being dimensioned to support the graft in a semi-expanded state.
The angiographic guidewires may be of any resilient type known to those skilled in the art which is formed to have memory, i.e., being capable of, upon deformation, generally returning to a pre-deformation shape. Each guidewire is bent to define, in a natural state, a loop and a segment with the segment including a generally straight first portion extending from the loop, and a generally straight second portion extending from the first portion and through the supported vascular graft. The loops are formed with frangible connections, such as through welding, which allow for the loops to be respectively torn open upon sufficient application of force. Further, the second portions of both guidewires are joined together along the respective lengths thereof, with the joined second portions extending through the loops of both guidewires to define a common shaft of the instrument.
With the loops supporting the vascular graft, the loops are dimensioned to partially expand the graft circumferentially and allow for passage of an unexpanded stent thereinto with the stent being threaded over the common shaft. In this manner, the stent may be introduced inside the graft supported by the subject invention with circumferential expansion of the introduced stent further circumferentially expanding the partially-expanded graft.
The first embodiment is preferably used in conjunction with self-expanding stents. As described below, if a self-expanding stent is utilized, a distensible device, such as a angioplasty balloon, will be introduced separately from the stent to allow for proper removal of the invention and implantation of the graft. Alternatively, a stent may be utilized which is not self-expanding and requires mechanical force for expansion. In the alternative variation, the stent may be directly mounted to a distensible device, such as a angioplasty balloon.
In use of the first embodiment, a length of tubular graft material, any resilient graft material known to those skilled in the art which is expandable (e.g. PTFE), is mounted onto the invention with the loops being in engagement with the inner surface of the graft. The graft and the loops are then caused to be collectively collapsed with the graft being circumferentially compressed substantially about the common shaft and the loops being interposed between the graft and the common shaft in distorted states. Preferably, the graft and the loops are maintained in the collapsed position by a lubricous plastic being tightly disposed about the graft. Once collapsed, the assembly is introduced into the bloodstream and guided therethrough using techniques known to those skilled in the art. The graft is properly positioned in the desired location with the ends of the graft being aligned with healthy portions of blood vessel found at axially-spaced locations about the anomaly which is being treated. Thereafter, the lubricous plastic is removed from the graft, thus, allowing the loops to regain memory and bias the graft into a semi-expanded state, with a passage being defined through the graft.
With the graft being partially expanded, an unexpanded stent is introduced inside of the graft to provide reinforcement for supporting the graft. In the preferred variation of the first embodiment, a self-expanding stent is introduced inside of the semi-expanded graft by threading and advancing the stent over the common shaft of the invention. With the stent being aligned with the graft, the stent is allowed to expand, which causes the graft to be further expanded. Afterwards, a distensible device, such as an angioplasty balloon, is introduced inside of the semi-expanded stent and graft assembly. The distensible device is caused to be expanded which, in turn, causes the stent and graft assembly to become fully expanded with the graft coming into pressing engagement with healthy portions of the blood vessel wall. Simultaneously, the expansion of the distensible device will cause the frangible connections used to form the loops of the invention to break, thus breaking the loops. The distensible device is then deflated and withdrawn, and, finally, the invention is withdrawn from the blood vessel with the portions of the guidewires which define the loops being pulled out from between the expanded stent and expanded graft upon withdrawal of the invention. As a result of this procedure, a fully expanded stent-reinforced graft is implanted at a desired location in a blood vessel.
In alternate variations of the first embodiment of the invention, thread can be wrapped about th
Casella Anthony J.
Hespos Gerald E.
Montefiore Hospital and Medical Center
Porco Michael J.
Robert Eduardo C.
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