Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
1999-02-09
2001-04-24
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001230, C623S001160, C606S108000
Reexamination Certificate
active
06221096
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to self-expandable intravascular stents for use in the treatment of ectatic vascular diseases (such as aneurysm) and more particularly to intravascular stent catheters that not only expand on their own when they are pressed in from outside the body but also can be afterward constricted and recovered.
BACKGROUND OF THE INVENTION
An aneurysm is an unfavorable condition resulting from arterial sclerosis, inflammation and other causes that will grow larger and lead to fatal ruptures when left unattended. Since current medicinal treatments hardly produce any good results, excision and replacement of dilatations have conventionally been resorted to. However, this condition appears frequently in aged persons and is often associated with the disturbances of many organs (such as the brain, heart and liver). Therefore, applicability of surgical operations, which can often cause exorbitant stresses, is limited. Thus, intravascular treatments using catheters whose operative stresses are relatively moderate have been receiving the attention of the world. The use of stents is one of such treatments in popular use.
The stent is a term to generally denote artificial tubular structures that are inserted into blood vessels and other tubular organs in the body to support them. When, for example, stricture or other defamation has occurred in blood vessels, gallbladers, gullets, bowels, ureters and other internal tubular organs, a stent is inserted into them to prevent the recurrence of such stricture or deformation by supporting them. Generally, the main body of the stent is elastic, being made of metal wires or other similar materials. The main body of the stent is designed so that it can radially expand and constrict repeatedly. The stent is often inserted in the body using a catheter. Therefore, the stent must become smaller than the inside diameter of the catheter when it constricts so that it can be contained within the catheter. When released from inside the catheter, the stent must radially expand to the desired diameter.
Several types of self-expanding stents having elastic tubular shapes are made of wires of stainless steel, shape memory alloy or other metals and are intended for use in blood vessels for the treatment of aneurysm, as disclosed, for example, in Japanese Provisional Patent Publications Nos. 24072 and 47134 of 1995 and Japanese Provisional Patent Publications Nos. 500272 of 1995 and 299456, 502428 and 511437 of 1996. These self-expanding stents are mainly used as stent grafts (the term graft denotes an artificial blood vessel inserted into a human blood vessel) that are sutured and fixed in laminar polyester blood vessels. A stent graft compressed and loaded in a thin catheter is pressed into an aneurysm from a part of a peripheral artery (mainly the femoral artery by way of the catheter). The stent graft is then allowed to expand on its own and dwell in the aneurysm to achieve both occlusion of the dilatation and repair of vascular flow. The intravascular treatment using stent grafts causes only mild operative stresses, thus lightening burdens of stresses imposed on patients and being applicable to wider varieties of aneurysms than conventional methods. This treatment is now very effective for cases of aneurysms.
To securely close an aneurysm by the use of an indwelling stent graft, it is necessary to keep the stent tightly fitted in the artery by ensuring that the stent covers not only the aneurysm itself but also the normal arteries at its center and on its peripheries. However, this can sometimes block up main arteries branching from the aneurysm and nearby sound aortas, which can lead to other organ derangements. The renal, inferior mesenteric and hypogastric arteries are the main visceral arteries affected by the dominal aneurysm. Occlusion of these arteries can lead to renal and intestinal ischemic dysfunctions. With aneurysms of the thoracic aorta, occlusion of the intercostal artery can cause disturbance of the spinal cord blood flow which, in turn, can result in a serious complication called paraplegia (lower-body motor paralysis).
However, the intravascular stents proposed so far cannot be re-constricted and recovered after they have been once released from catheters and allowed to expand on their own. As such, they present a serious problem in that they cannot be recovered from within the blood vessel even after an organ or blood flow derangement has occurred. In addition, if they have been placed in the wrong place, they are difficult to move to the right place for correction. Thus, their applicability is limited by safety considerations.
The object of this invention is to provide a stent that can be re-constricted and recovered after it has been released from a catheter and allowed to expand on its own.
SUMMARY OF THE INVENTION
An intravascular stent according to this invention comprises a self-expandable cylindrical stent proper that is connected to metal support wires having a long enough length to be extendable to outside the body via a catheter. Manipulation of the support wires pushes the stent proper from within the catheter into a blood vessel, allows it to repeatedly expand and collapse therein and return into the catheter.
Another intravascular stent according to this invention comprises a collapsible and expandable stent inserted in a catheter in a collapsed state that is adapted to be pushed out from the leading end of the catheter to a given position in a blood vessel. This intravascular stent comprises a stent proper, which, in turn, comprises an elastic, collapsible and expandable cylinder made of metal wires and multiple connecting wires spaced around the circumference of the elastic cylinder, extending along the longitudinal axis of the elastic cylinder so as to intersect with the metal wires constituting the elastic cylinder and fastened to the elastic cylinder at the points of intersection with the metal wires thereof, and support wires extending backward from the stent proper and throughout the entire length of the catheter.
The catheter contains the stent in a collapsed condition. In administering medical treatment, the catheter is driven to the desired position in a blood vessel of a patient, and then the stent proper is pushed out from within the catheter into the blood vessel by pressing the support wires from outside the body of the patient. The stent proper pushed out from the catheter expands on account of its own elasticity. To leave the stent proper temporarily in the blood vessel, the whole of the stent proper is retracted back into the catheter by pulling the support wires from outside the body after a given time. When the support wires are pulled, the support wires and stent proper contract at the exit end of the catheter. The stent proper can be repeatedly expanded and contracted and pushed out from and retracted back into the catheter. The stent is thus brought exactly to the desired point.
At least one of the stent proper and support wires may have a superelastic deformable part made of nickel-titanium-based alloy or other shape-memory alloy wires that exhibit superelasticity substantially at 37° C. Shape-memory alloys have a superelastic property that exhibits an elastic limit 15 to 20 times higher than that of ordinary metals above a certain temperature. Because of this superelastic property, shape-memory alloys are suited for the manufacture of best-quality stents that can maintain the original shape even after repeating release and retraction many times. This superelasticity appears above a certain specific temperature called the transformation temperature indigenous to each material. The shape-memory alloys suited for the stents should have a transformation temperature that is controlled so that superelasticity appears at least at 37° C. (body temperature).
The stent proper can be fastened by stitching to artificial blood vessels made of polyester films, thereby increasing the affinity between the stent and living body.
This invention permits placing a recoverable temporary s
Aiba Mitsuru
Ishimaru Shin
Jackson Suzette J.
Kanto Special Steel Works Ltd.
Wenderoth Lind & Ponack, LLP.
Willse David H.
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