Intravascular stent with extendible end rings

#The invention relates to vascular repair devices, and in particular intravascular stents, which are adapted to be implanted into a patient's body lumen, such as a blood vessel or coronary artery, to maintain the patency thereof. Stents are particularly useful in the treatment of atherosclerotic stenosis in arteries and blood vessels.

#Stents are generally tubular-shaped devices which function to hold open a segment of a blood vessel or other body lumen such as a coronary artery. They also are suitable for use to support and hold back a dissected arterial lining that can occlude the fluid passageway. At present, there are numerous commercial stents being marketed throughout the world. For example, the prior art stents depicted in FIGS. 1-5 have multiple cylindrical rings connected by one or more undulating links. While some of these stents are flexible and have the appropriate radial rigidity needed to hold open a vessel or artery, there typically is a tradeoff between flexibility and radial strength and the ability to tightly compress or crimp the stent onto a catheter so that it does not move relative to the catheter or dislodge prematurely prior to controlled implantation in a vessel.

#Presently, there is substantial development of drug coated stents, particularly in the coronary arteries, to reduce the likelihood of the development of restenosis after the stent has been implanted. One problem being encountered with stent, including these drug coated stents, is that restenosis can sometimes occur at the stent ends, both distally and proximally of the implanted stent. The development of restenosis at the stent ends is sometimes referred to as peri-stent restenosis. While various theories exist as to the reasons for the development of restenosis at the stent ends, one important factor appears to be injury to the arterial wall by the non-working length of the balloon. In other words, that portion of the balloon that extends beyond the stent will expand into the arterial wall and cause stretching or other injury that will eventually lead to the development of restenosis. The drug coating on the stent will release the drug substantially in the area where the stent contacts the arterial wall, leaving the distal and proximal areas beyond the stent untreated with the therapeutic drug. As a result, the likelihood of the development of restenosis beyond the ends of the stent is much greater since the therapeutic drug does not treat that injured area.

#FIG. 1 is an elevational view, partially in section, of a prior art stent mounted on a rapid-exchange delivery catheter and positioned within an artery.

#FIG. 2 is an elevational view, partially in section, similar to the stent shown in FIG. 1 wherein the prior art stent is expanded within the artery, so that it embeds within the arterial wall.

#FIG. 3 is an elevational view, partially in section, showing the expanded prior art stent implanted within the artery after withdrawal of the rapid-exchange delivery catheter.

#The present invention stent improves on existing stents by providing a longitudinally flexible stent having a uniquely designed pattern of expandable cylindrical rings with stent end rings that lengthen as the rings expand radially outwardly. A distal end ring lengthens distally in a longitudinal direction and a proximal end ring extends and lengthens longitudinally in the proximal direction as the stent expands due to the unique and novel twin peak design. The stent can be drug coated so that the therapeutic drug is delivered by the extended end rings to reduce the likelihood of the development of peri-stent restenosis. In addition to providing longitudinal flexibility, the stent of the present invention also provides radial rigidity and a high degree of scaffolding of a vessel wall, such as a coronary artery.

#Turning to the drawings, FIG. 1 depicts a prior art stent 10 mounted on a conventional catheter assembly 12 which is used to deliver the stent and implant it in a body lumen, such as a coronary artery, peripheral artery, or other vessel or lumen within the body. The catheter assembly includes a catheter shaft 13 which has a proximal end 14 and a distal end 16. The catheter assembly is configured to advance through the patient's vascular system by advancing over a guide wire by any of the well known methods of an over the wire system (not shown) or a well known rapid exchange catheter system, such as the one shown in FIG. 1.

#Catheter assembly 12 as depicted in FIG. 1 is of the well known rapid exchange type which includes an RX port 20 where the guide wire 18 will exit the catheter. The distal end of the guide wire 18 exits the catheter distal end 16 so that the catheter advances along the guide wire on a section of the catheter between the RX port 20 and the catheter distal end 16. As is known in the art, the guide wire lumen which receives the guide wire is sized for receiving various diameter guide wires to suit a particular application. The stent is mounted on the expandable member 22 (balloon) and is crimped tightly thereon so that the stent and expandable member present a low profile diameter for delivery through the arteries.