The acute effect of stenting with the nitinol self-expanding coil stent: preliminary experience

Background. The acute angiographic results with the self-expanding nitinol stent have not been reported. We aim to provide angiographic data of the effect of self expansion and balloon assistance on the results. This is analyzed with respect to stent gain, arterial- and stent-recoil. Methods and Results. The self-expanding nitinol coil stent is inherently different than balloon-expandable stents in its mechanism of deployment and the way that radial arterial expansion is achieved. Between January 1995 and June 1996, 86 stents were deployed in 64 patients undergoing elective angioplasty at the Rambam Medical Center, Haifa, Israel. The stent deployment procedure involved stent release assisted by high pressure balloon dilatation. The baseline, post-balloon, post-stenting and post-stent-dilatation characteristics were recorded with similar views, digitized to a PC and analyzed by image processing software. Using computerized analysis, arterial- and stent-recoil and stent gain were calculated for the average stented segment lesion (0.48 ± 0.42, 0.22 ± 0.37, 0.28 ± 0.37, respectively). Balloon angioplasty increased the minimal luminal diameter from 1.07 ± 0.73 mm at baseline, to 2.24 ± 0.57 mm; stent deployment further increased the diameter to 2.63 ± 0.48 mm, and within-stent balloon dilatation to 2.96 ± 0.62 mm. Conclusions. The self-expanding nitinol stent exerts its effect on both the MLD and the average stented diameter through its intrinsic radial force aided by post-deployment within-stent balloon dilatation. A significant correlation was found between stent gain and arterial recoil (slope = 0.59, r = 0.68, p<0.001) but not with stent-artery recoil. Therefore, with the negligible effect of stent recoil, the acute benefit of the nitinol stent is directly proportional to arterial recoil, a feature which is also common to balloon-expandable stents.