Oversizing of self-expanding stents: influence on the development of neointimal hyperplasia of the carotid artery in a canine model.

BACKGROUND AND PURPOSE In carotid artery stent placement, marked oversizing of the stent relative to the internal carotid artery lumen is common. This study was performed to determine the influence of using oversized self-expanding nitinol stents on neointimal hyperplasia. METHODS In six greyhound dogs, 24 self-expanding nitinol stents (eight SMART stents, eight Easy Wallstents, eight Sinus-Flex stents) were inserted into both common carotid arteries (CCAs). In each CCA, two stents were deployed; a stent of the appropriate diameter was implanted distally and an oversized stent proximally. After 4 months, transverse sections of each stent were examined histologically and at computerized image analysis. Neointimal hyperplasia was determined as the proportion of the residual diameter of the patent vessel lumen compared with the stent lumen. RESULTS The amount of neointimal hyperplasia did not differ between the normal-sized and oversized stents. The mean preserved luminal diameter (+/-SEM) with normal- and oversized stents, respectively, were as follows: Easy Wallstent, 94% +/- 1.0 and 96% +/- 1.5; SMART stent, 92% +/- 1.6 and 93% +/- 1.8; and Sinus-Flex stent, 93% +/- 2.7 and 93% +/- 2.6. The mean preserved patent lumen with the 12 normal-sized stents (93% +/-1.0) was not significantly different from that of the 12 oversized stents (94% +/- 1.1, P =.502). CONCLUSION Under experimental conditions, use of self-expanding stents oversized by 30-40% appeared to result in neointimal hyperplasia comparable to that caused by normal-sized stents. All three stent types appeared to have similarly low neointimal responses.