Balloon catheters and stents are normally used for treating blood vessel constrictions. Although balloon catheters are effective in removing constrictions, they can not only result in a dissection in the blood vessel (which causes the vessel to close and acute myocardial infarction to occur) but also increase the risk of another constriction occurring in the same portion of the blood vessel at a later time. Stents are commonly employed to overcome these problems. Stents are hollow tubes that are implanted inside of the blood vessel to "prop" the vessel open and prevent blood vessel constrictions and blockages.
Stents are available in a variety of configurations including self-expanding springs, mechanically actuated expandable devices, heat actuated expandable devices, and expandable sleeves. Of these various configurations, expandable sleeves are the most promising. Expandable sleeves are mounted on a collapsed catheter balloon and, after introduction into the vessel, expanded through the elastic limit of the metal by balloon expansion. The permanently deformed sleeve contacts and supports the interior wall of the blood vessel.
Though widely used, stents can have a number of limitations and can cause health complications. For example, stents can be limited in the radial strength of the stent (thereby limiting the amount of support provided to the interior wall of the blood vessel), in the maximum size of the stent (e.g., maximum stent diameter) after expansion (thereby limiting the stent to use in smaller diameter vessels), and/or in the minimum size of the stent profile that is to be inserted into the vessel (thereby limiting the stent to use in larger diameter vessels). Stents can also cause health complications after implantation including thrombogenic occlusion of the blood vessel (e.g., blood clots), restenoses (e.g., narrowing of the lumen of the blood vessel), and injury to the interior wall of the blood vessel wall during stent insertion, which can cause bleeding.
There is a need for a stent having a relatively high radial strength and therefore a relatively low risk of failure during use.
There is a further need for a stent having a broad range of sizes after expansion for use in blood vessels of a variety of sizes.
There is a further need for a stent having a low risk of injury to the blood vessel during insertion.
There is a further need for a stent that has a low risk of thrombosis after implantation in a blood vessel.
There is a further need for a stent that has a relatively low incidence of restenoses after implantation.