Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2000-10-24
2003-09-02
Vanatta, A. (Department: 3765)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
Reexamination Certificate
active
06613080
ABSTRACT:
BACKGROUND OF THE ART
Stents of that kind are known from the state of the art in many different forms. Those stents are used inter alia in connection with percutaneous transluminal angioplasty (PCTA, Percutaneous Transluminal Balloon Angioplasty), in vascular surgery of the heart. Stents however can also serve to dilate other openings in the body or to keep such openings in a dilated condition. That medical procedure is initially preceded by determining the location of the constriction in a coronary blood vessel. A so-called angioplasty balloon is then moved in the artery which has the constriction, the so-called stenosis, to the location of the stenosis where it is inflated. Due to the radially outwardly directed force of the inflated balloon the constriction is dilated and in the optimum case the original passage cross-section of the previously constricted artery is restored. Besides successful dilation of the vessel however side-effects can also occur, which include local splits in the artery, disintegration effects and projections of plate portions and flakes into the lumen of the artery so that, in spite of the dilation effect, blockage of the vessel can still occur. In addition it is possible that a stenosis can recur due to the vessel wall elastically springing back and/or due to the growth of the intima of the vessel. Statistically, that occurs within six months in the case of over 30% of the patients who were treated with PCTA.
In order now immediately after dilation of the vessel to ensure a relatively smooth inside wall surface for the vessel and to be able to avoid renewed stenosis, the stents set forth in the opening part of this specification were developed. Those small tubes serve inter alia in conjunction with PCTA to maintain the vessel flow cross-section which is produced by balloon angioplasty in order thereby to ensure long-term success with the PCTA procedure.
The success of such so-called stenting also depends inter alia on how uniformly the stent can come to bear against the wall of the vessel. For, the more uniformly the wall of the vessel is supported, the correspondingly more probable it is that vessel constrictions will not recur in the region of the stent. In that respect a regular stent structure produces a relatively smooth inside surface for the vessel and, with a relatively smooth inside vessel surface, blood particles can only be deposited thereon with difficulty. In addition growths of the intima into the interior of the vessel are prevented to a greater degree by a regular stent structure which covers over the inside surface of the vessel in a relatively closed configuration.
Stents of that kind with a so-called closed structure are also known from the state of the art. By way of example reference may be made here to one of the best-known stents of that kind, the so-called wall stent. That is known for example from U.S. Pat. No. 4,655,771. This stent which has a closed structure is formed from a plurality of wires which are regularly knitted in a mesh-like structure and which extend in a spiral configuration on the longitudinal axis of the stent.
The advantage of the closed structure of stents of that kind is however only achieved at the cost of the disadvantage that the stents involve relative longitudinal stiffness during insertion. Those stents do not therefore make it possible in the optimum manner for the stent to be guided through possibly very severely curved vessel portions in the coronary arteries upon insertion in a direction towards the stenosis to be treated. In order to avoid those disadvantages of a closed structure, stents have now been developed which are of a so-called modular nature. In the case of those stents of a modular nature, individual portions which are provided with a closed structure are connected together by flexible connections. Stents of that kind are known for example from U.S. Pat. No. 5,104,404.
A disadvantage with those modular or segmented stents however is that the front edges of each individual module or segment, which lead in the direction of insertion of the stent, can hook in the inside wall of the vessel. That can give rise to serious complications when inserting a stent. That is particularly problematical more especially insofar as the modular stents—as already referred to above—are used in particular when major curvatures have to be negotiated on the way to the location to be treated. For, it is in such a curve that such a leading edge of a segment becomes particularly easily hooked at the inside surface of the vessel, which is on the outside of the curvature, through which the stent is being passed.
Therefore the object of the invention is to avoid the above-mentioned disadvantages and to provide a stent of the kind set forth in the opening part of this specification which both permits the inside surface of the vessel to be covered in a closed configuration at the location of the stenosis to be treated while at the same time it is sufficiently flexible that it can be displaced to that location.
SUMMARY OF THE INVENTION
In the case of the present invention that object is attained by a stent of the kind set forth in the opening part of this specification, in that the openings provided in the stent are of a substantially T-shaped configuration.
The advantages of the invention are in particular that the T-shaped openings in the tubular structure of the stent provide a structure which is closed overall so as to provide for good covering of the lesion while at the same time by virtue of the T-shaped openings the flexibility in the longitudinal direction of the stent is increased in comparison with the closed stent structures which are known from the state of the art.
The invention involves the realization that the openings which are of a T-shaped configuration in accordance with the invention mean that those openings have two portions which extend substantially perpendicularly to each other. These involve on the one hand the portion of the opening, which forms the crossbar of the T-shape, and the portion of the opening, which forms the upright leg of the T-shape. In this case the crossbar of the T-shape preferably extends in the longitudinal direction of the tubular portion of the stent while the upright leg of the T-shape preferably extends in the peripheral direction of the tubular portion of the stent according to the invention. That configuration ensures that the stent has flexibility in both of the above-mentioned directions, such flexibility imparting to the stent according to the invention overall a degree of flexibility as is required for example when pushing the stent through curves in coronary blood vessels.
In a preferred configuration of the present invention the tubular portion has a peripheral surface, wherein the openings in the tubular portion are defined by bars, which bars are formed from the remaining material of a tube wall, forming the peripheral surface, of the tubular portion, the material having been removed from that tube wall in the region of the openings. This embodiment is distinguished in that the bars define the openings in the direction of the longitudinal axis of the tubular portion, substantially in the form of an S. This embodiment is advantageously distinguished in that an enhanced degree of flexibility of the stent is achieved by virtue of the S-shaped bars defining the openings, as the S-shape is inherently flexible. In addition, with this embodiment it is preferred if the S-shaped bars are arranged in such a way that the respective S-shape formed is disposed in the peripheral direction. For, in that way it is possible for the respective curve or bulge portions of the S-shape, upon insertion of the stent into curved coronary blood vessels, to be pushed into the adjacent bend configuration or the adjacent bulge portion of the same S-shape or the peripherally adjacent S-shape of the bars in order in that way to guarantee stent flexibility. A further advantage of this embodiment is that when crimping of the stent is effected a smaller crimp profile is produced. With thi
Biotronik Mess -und Therapiegeraete GmbH & Co. Ingenieurbuero Be
Grant Stephen L.
Hahn Loeser + Parks LLP
Vanatta A.
LandOfFree
Stent with closed structure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stent with closed structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stent with closed structure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3037690