Continued expansion of the nitinol self-expanding coronary stent: Angiographic analysis and 1-year clinical follow-up

Background This study sought to report the first-year clinical outcome with the nitinol self-expanding coil stent and to provide angiographic data on the effect of self-expansion during implantation and follow-up. Self-expend ing stents do not reach their nominal diameter at implantation. The long-te rm effects may therefore depend, in port, on continued expansion after init ial implantation. Methods Between January 1995 and January 1996, 86 stents were deployed in 6 4 patients for indication of suboptimal results. All patients were clinical ly followed up for 1 year, and 72% had follow-up angiography. Results The majority (55%) of the lesions were class B2 or C. Balloon angio plasty increased the minimal lumen diameter from 1.07 +/- 0.73 mm to 2.24 /- 0.57 mm; stent deployment further increased the diameter to 2.63 +/- 0.4 8 mm, and within-stent balloon dilatation to 2.96 +/- 0.62 mm. Angiographic follow-up performed at 7.8 +/- 1.1 months (range 7-9 months) showed that t he minimal lumen diameter was 2.15 +/- 0.80 mm (late lumen loss of 0.81 +/- 0.69 mm), and the mean stent diameter expended to 3.58 +/- 0.48 mm (self-e xpanding late stent gain of 0.62 +/- 0.55 mm). The extent of this expansion was inversely related to the late lumen loss (r = 0.67, slope 0.81, P <.01 ). At 1 year 51 (80%) of 64 patients were event free; 3 had undergone coron ary artery bypass grafting, 2 had had a myocardial infarction, and 9 had re peat angioplasty. In the subgroup of a simple lesion (<15 mm) covered by 1 stent, 18 (86%) of 21 patients were event free. Conclusions The self expanding nitinol stent exerts its acute effect on min imal lumen diameter through its intrinsic radial force aided by balloon exp ansion. The stent continues to expand until it reaches its nominal diameter over the follow-up period. The extent of this expansion is inversely relat ed to the late lumen loss, leading to an acceptable rate of long-term clini cal events in this first cohort of patients with complex disease morphology .