Stent having a multiplicity of undulating longitudinals
A method for implanting a balloon expandable stent at a site within a passageway of a curved coronary article. The stent includes at least two longitudinally spaced apart circumferential rings. At least one longitudinally extending connector extends between adjacent rings. The connector has at least one turn back portion that can expand or contract in length while being passed through a curved passageway. The stent is disposed on a stent delivery catheter having an inflatable balloon. The stent delivery catheter and the stent is delivered through the passageway to the site of implementation with the connector member expanding or contracting in length to facilitate delivery and placement of the stent. The stent is expanded at the site of implantation by inflating the balloon to force the stent radially outward against the wall of the coronary artery.
This invention is in the field of stents for maintaining patency of any one of a multiplicity of vessels of the human body.
BACKGROUND OF THE INVENTIONIn the last decade, many different designs of stents have been used to maintain patency of arteries and other vessels of the human body. In all such devices, hoop strength is an important characteristic. Specifically, the stent must have enough hoop strength to resist the elastic recoil exerted by the vessel into which the stent is placed. The Mass stent described in the U.S. Pat. No. 4,553,545 and the Dotter stent described in U.S. Pat. No. 4,503,569 are each open helical coils. The Palmaz stent described in the U.S. Pat. No. 4,733,665 is of the “chinese finger” design. The Gianturco-Rubin stent currently sold by Cook, Inc, is another stent design which like the stents of Mass, Dotter and Palmaz does not have any closed circular member to optimize hoop strength.
The ideal arterial stent utilizes a minimum wire size of the stent elements to minimize thrombosis at the stent site after implantation. The ideal arterial stent also possess sufficient hoop strength to resist elastic recoil of the artery. Although the optimum design for maximizing hoop strength is a closed circular structure, no prior art stent has been described which has a small diameter when percutaneously inserted into a vessel and which expands into the form of multiplicity of closed circular structures (i.e. rings) when expanded outward against the vessel wall.
BRIEF SUMMARY OF THE PRESENT INVENTIONThe present invention is an expandable stent that can be used in an artery or any other vessel of the human body which, when expanded, forms a multiplicity of generally circular rings whose closed structure optimizes hoop strength so as to minimize elastic recoil of the vessel into which the stent is inserted. Furthermore, the structure of the stent in the present invention is initially in the form of folded ellipses or ovals which can be formed to a small diameter for percutaneous insertion by means of a stent delivery catheter. The ovals are joined to each other by either a straight or undulating shaped wires which are called “longitudinals” which serve to space the deployed rings within the vessel. Straight longitudinals are used in straight vessels and undulating longitudinals can be employed in either straight or highly curved vessels such as some coronary arteries.
Thus, an object of this invention is to provide a stent having a maximum hoop strength by the employment of closed, generally circular structures which are in fact rings.
Another object of this invention is that the rings are initially in the form of ovals that can be folded to fit onto a cylindrical structure at a distal portion of a stent delivery catheter.
Still another object of this invention is that the fully deployed rings are spaced apart by means of longitudinals which are either straight of undulating wires that are placed to be generally parallel to the longitudinal axis of the vessel into which the stent is deployed.
Still another object of this invention is that the pre-deployment stent structure is formed as a single piece out of a metal tube having a smaller inside diameter as compared to the outside diameter of an expandable balloon onto which the pre-deployment stent is mounted.
These and other important objects and advantages of this invention will become apparent from the detailed description of the invention and the associated drawings provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
To place the stent design of
FIGS. 1 to 7 inclusive illustrate stents that employ longitudinals that are formed from generally straight wires.
Typically, the rings and longitudinals of the stents would be made of the same material. Typical metals used for such a stent would be stainless steel, tantulum, titanium, or a shape memory metal such as Nitinol. If Nitinol is used, the stent would be heat treated into the shape at body temperature having circular rings 2 as shown in
It should be understood that once the ovals are folded onto a stent delivery catheter, when they fully deploy, they do not form perfectly circular rings as shown in
It should also be understood that at least part of the end rings of the stent could be fabricated from or coated with a radiopaque metal such as tantalum or gold to provide a fluoroscopic indication of the stent position within a vessel. However, the other rings and the longitudinals could be made from a much less dense metal which would provide less obscuration of the central region within the stent. For example, the stent rings and longitudinals could all be fabricated from titanium or a titanium alloy except the end rings which could be formed from gold which is then plated with titanium. Thus, the entire outside surface of the stent would be titanium, which is known to be a comparatively non-thrombogenic metal while the gold in the end rings provides an improved fluoroscopic image of the stent extremities.
The dimensions of stent rings are typically 0.1 to 0.3 mm thick, with a width of 0.1 to 0.5 mm and an outside diameter D between 2.0 and 30.0; mm depending on the luminal diameter of the vessel into which it is inserted. The length of the stent could be between 1 and 10 cm. The wire diameter for the longitudinals would typically be between 0.05 and 0.5 mm.
Although the designs of
It is further anticipated that a pre-deployment stent structure 20 as shown in
Various other modifications, adaptations, and alternative designs are of course possible in light of the above teachings. Therefore, it should be understood at this time that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
Claims
1. A post-deployment stent structure for maintaining patency of a vessel of a human body comprising:
- a multiplicity of closed, generally circular rings, the plane of each ring being generally parallel to the plane of each adjacent ring, the rings having a common longitudinal axis which is perpendicular to the plane of each ring and which longitudinal axis passes through the geometric center of each ring; and
- a multiplicity of elongated wire structures forming longitudinals which longitudinals are fixedly attached to the rings so as to be generally parallel to the longitudinal axis of the rings.
2. The stent of claim 2 wherein the rings have a multiplicity of cutouts for the placement therethrough of the longitudinals.
3. The stent of claim 2 wherein the cutouts on the rings are notches.
4. The stent of claim 3 wherein the notches on the rings are located at the outside perimeter of each ring.
5. The stent of claim 3 wherein the notches are located at the inside perimeter of each ring.
6. The stent of claim 2 wherein the cutouts are holes drilled through the rings.
7. The stent of claim 1 wherein the longitudinals are essentially straight wires.
8. The stent of claim 1 wherein at least two of the longitudinals are of an undulating shape.
9. The stent of claim 1 wherein the longitudinals are welded to the rings.
10. The stent of claim 1 wherein the rings and longitudinals are made from or coated titanium.
11. The stent of claim 1 wherein the end rings are more radiopaque as compared to any other ring.
12. The stent of claim 1 wherein the stent is formed from a metal having a shape memory characteristic.
13. An initial structure that is capable of being formed into a pre-deployment stent structure which in turn is capable of being deployed into a post-deployment stent structure for placement within a vessel of the human body, the initial structure comprising:
- a multiplicity of flat ovals, the plane of each oval being generally parallel to the plane of all other ovals, the ovals having a common longitudinal axis which is perpendicular to the plane of each oval and which longitudinal axis passes through the geometric center of the ovals; and
- a multiplicity of longitudinals which are fixedly attached to the ovals, the longitudinals being positioned onto the ovals so as to be generally parallel to the longitudinal axis of the ovals.
14. The initial structure of claim 12 wherein the ovals and the longitudinals are formed from a single piece of metal.
15. A generally cylindrical pre-deployment stent structure which is capable of being deployed into a post-deployment stent structure for placement within a vessel of the human body, the pre-deployment structure being formed from an initial structure which consists of a multiplicity of flat ovals, the plane of each oval being generally parallel to the plane of all other ovals, the ovals also having a minor axis and a major axis and a minor axis dimension and a major axis dimension; the ovals having a common longitudinal axis which is perpendicular to the plane of each oval and which longitudinal axis passes through the geometric center of the ovals; and a multiplicity of longitudinals which are fixedly attached to the ovals, the longitudinals being positioned onto the ovals so as to be generally parallel to the longitudinal axis of the ovals;
- the pre-deployment stent structure being formed by folding the ovals around a distal portion of a stent delivery catheter, the pre-deployment stent structure being adapted to form a post-deployment stent structure having a multiplicity of generally circular rings that are formed from the ovals, the circular rings being joined together by the longitudinals.
16. The pre-deployment stent structure of claim 15 wherein the ovals are folded around an expandable balloon located near the distal end of the stent delivery catheter.
17. The pre-deployment stent structure of claim 15 wherein the ovals are folded around the oval's minor axis to form a generally cylindrical shape that can be mounted onto a stent delivery catheter.
18. The pre-deployment stent structure of claim 15 wherein one side of the ovals is folded in one direction and the opposite side of the ovals is folded in the opposite direction to form a pre-deployment structure of a generally cylindrical shape.
19. The pre-deployment stent structure of claim 15 wherein the outer diameter of the generally cylindrical pre-deployment stent structure is approximately the same as the minor axis dimension of the oval.
20. The pre-deployment stent structure of claim 15 wherein the stent structure is a cylinder formed from a single piece of metal, the cylinder being slightly smaller in its inside diameter as compared to the outside diameter of an expandable balloon located at a distal portion of a stent delivery catheter onto which the stent structure is mounted.
Type: Application
Filed: Jul 12, 2005
Publication Date: Nov 3, 2005
Inventors: Robert Fischell (Dayton, MD), David Fischell (Fair Haven, NJ), Tim Fischell (Nashville, TN)
Application Number: 11/179,424