NEOINTIMAL HYPERPLASIA IN LOW-PROFILE NITINOL STENTS, PALMAZ STENTS, AND WALLSTENTS - A COMPARATIVE EXPERIMENTAL-STUDY

Purpose: To compare neointima formation following insertion of low-pro file Nitinol stents, Palmaz stents, and Wallstents. Methods: Nitinol s tents, Palmaz stents, and Wallstents similar in size were transfemoral ly inserted into the iliac arteries of 12 sheep, Four stents per sheep were deployed; the position of the stents was varied so that each typ e of stent was placed in each position (right or left, proximal or dis tal) with equal frequency. Stent patency was followed by angiography, Six sheep were euthanized after 1 month, and the remaining six after 6 months. Iliac arteries were removed en bloc and prepared for histolog ical examination. Neointimal and medial thickness were measured by Lig ht microscopy, and measurements were analyzed statistically. Results: Mean neointimal thickness both over (NO) and between (NB) the stent st ruts was greater in Wallstents (NO = 0.341 mm, NB = 0.368 mm) than in the Nitinol (NO = 0.260 mm, NB = 0.220 mm) and Palmaz stents (NO = 0.1 99 mm, NB = 0.204 mm), but differences were not significant (p > 0.05) . Medial atrophy in the area between the stent struts was greater in W allstents compared with Nitinol and Palmaz stents (p < 0.007 and p < 0 .02, respectively); in the area under the stent struts there was a sig nificant difference only between Palmaz stents and Wallstents (p < 0.0 2). Conclusion: Under defined experimental conditions, none of the thr ee types of stent appears to be preferable to the others regarding neo intima formation in the short- to mid-term follow-up period.