Percutaneous transluminal angioplasty is one therapy used for selected atherosclerotic lesions to relieve stenosis of body lumens. While angioplasty has gained wide acceptance, abrupt closure and restenosis often occur following the procedure.
Endovascular stents have been used to mechanically block abrupt closure and restenosis of the lumen. Such stents are commonly made of metal or plastic and a variety of stents have been proposed and patented. Radially expandable stents formed of shape-memory alloys (Schnepp-Pesch, U.S. Pat. No. 5,354,309) and of polymers (Hickle, U.S. Pat. No. 5,139,480; Palmaz, U.S. Pat. No. 4,739,762), including shape-memory polymers (Froix, U.S. Pat. No. 5,163,952) have been described. One limitation of some of these stents is the axial expansion that occurs with the radial expansion. Axial expansion can make it difficult to size and correctly place the stent at the target site. Some stents are also often limited in expansion ratio, capable of expanding radially only two or four-fold.