Untitled record

ES 2 352 002 T3

DESCRIPTION

Background of the Technique

Stents are commonly used as tubular structures that are left within the lumen of a canal to relieve an obstruction. Commonly, stents are inserted into a lumen in their unexpanded form and then expanded in situ autonomously (or with the aid of a second device). A typical expansion procedure occurs through the use of a catheter-mounted angioplasty balloon, which is inflated within the blood vessel or body passage in which the stent has been applied, to cut and break the obstructions associated with the components of the blood vessel wall and to enlarge the lumen.

In the absence of a stent, restenosis can occur as a result of elastic recoil from a stenotic lesion. Although various stent designs have been reported, these designs suffer from various limitations. These include restrictions on the dimensions of the stent.

Other stents are described as longitudinally flexible but consist of a plurality of cylindrical elements connected to each other. This design has at least one major drawback. For example, according to this design, protruding edges are produced when the stent flexes around a curve, with the possibility of inadvertent retention of the stent in plaque deposited on the arterial walls. This can cause the stent to form an embolus or move relative to its position and further damage the inner lining of healthy blood vessels.

Therefore, stents are known in the art. Such stents can be expanded during or just after balloon angioplasty. As a general rule of thumb, stent fabrication will need to compromise axial flexibility to allow for expansion and provide overall structural integrity.

Previous stents had a first end and a second end with an intermediate section between the two ends. Additionally, the stent has a longitudinal axis and comprises a plurality of longitudinally arranged bands, each band defining a generally continuous wave along a linear segment parallel to the longitudinal axis. A plurality of links hold the bands in a tubular structure.

It has been observed, however, that it may be desirable to provide stents that have both the flexibility to navigate a tortuous lesion and greater spinal strength to maintain the necessary rigidity after placement in the body lumen. The

ES 2 352 002 T3 Preferred designs tend to provide flexibility through undulating longitudinal connectors. Rigidity is generally achieved by a slotted, tubular stent mechanism. It has been observed that there may be mechanisms capable of improving the characteristics of these types of stents. Such a stent would be both flexible upon implantation and rigid upon placement.

EP-0970664 presents a radially expandable stent. It includes a first and a second partial structures. A first partial structure can be expanded in a radial direction. A second partial structure is almost rigid in the axial direction.

Summary of the Invention

An object of the invention is to provide a stent that has a relatively small shortening.

An object of the invention is to provide a stent having an improved degree of flexibility.

An object of the invention is to provide such a stent while minimizing any compromise in the structural rigidity of the stent as it expands.

These and other objectives of the invention are described in the following technical specification. In accordance with the present invention there is provided a stent as defined in appended claim 1. As described herein, a preferred embodiment of a stent provides a device that contains a flexible section and a folded strut section. The folded strut section opens (like a flower) upon expansion. This folded strut section provides both structural rigidity and reduced shortening of the stent mechanism. The flexible section provides flexibility to implant the stent mechanism.

These and other objects of the invention will be seen from the following drawings and Detailed Description of the Invention.

Detailed Description of Drawings

Figure 1A is a plan view of a stent embodying the invention.

Figure 1 is a schematic view of a stent embodying the invention.

Detailed description of the invention

ES 2 352 002 T3

As can be seen in Figure 1, a cylindrical stent 10 is described having a series of folded strut sections 20 connected by a series of flexible sections 30. The folded strut sections 20 comprise a generally folded strut element 25 having a pair of ends 24, 26. Each of the pair of ends 24, 26 is connected to another folded strut element 25 and also to the end of a flexible element 35. Therefore, each end 34, 36 of the flexible element 35 is connected to two ends 24, 26 of folded strut elements 25.

Each of the folded struts 25 adopts a generally irregular pattern. On the other hand, each of the flexible sections 35 adopts a generally wavy pattern. The folded strut sections 20 circumferentially surround the cylindrical shape of the stent 10. Each flexible section 30 also connects with a folded strut section 20 around the circumference of the stent. It will be noted that the adjacent flexible sections 30 are 180 ° out of phase with each other.

The longitudinal spans of the folded struts 20 are short enough to provide a smooth profile when the stent is bent. The folded strut 20 allows a high range of diametrical expansion when expanding. Therefore, when expanded, the folded struts 20 expand circumferentially and assume a ring shape with which maximum radial strength is achieved. Flexible elements 30 between the folded struts enhance stent delivery when the stent is in its unexpanded dimension.

In use, therefore, the stent 10 of the present invention is positioned on a balloon catheter and is snaked through the vascular system to be positioned at a site of injury in an artery, typically a coronary artery. Because the flexible sections 30 are substantially as flexible, they are capable of navigating tortuous lesions with relative ease. Once in place, the balloon catheter is expanded by conventional means. As they expand, the struts 25 of the folded strut sections 20 expand to obtain a hoop shape. Additionally, these elements expand longitudinally, thus avoiding any reduction by shortening. Of course, as they expand, the flexible elements 35 stretch so that the stent achieves additional strength in its stretched and rigid position.