Effects of P-32 radioactive stents on in-stent restenosis in a double stent injury model of the porcine coronary arteries

Background: The major limitation of coronary stenting remains in-stent rest enosis, due to the development of neointimal proliferation. Radioactive ste nts have demonstrated the ability to reduce this proliferation in the healt hy nonatherosclerotic porcine animal model. However, inhibition of tissue p roliferation in the in-stent restenotic lesion in a porcine model is not we ll characterized. The objective of this study was to examine the efficacy a nd safety of the P-32 radioactive stent for the treatment of in-stent reste nosis in a double stent injury model of the porcine coronaries. Methods and Materials: Eighteen coronary arteries in 9 pigs underwent nonra dioactive stent (8 mm in length) implantation. Thirty days after the initia l stent implantation, a 32P radioactive stent (18 mm in length) with an act ivity of 0 and 18 mu Ci was implanted to cover the initial stent. The swine were killed 30 days after the second stent implantation. Histomorphometric analysis was performed for vessel area (VA), stent strut area (SSA), intim al area (IA), and lumen area (LA). Results: Injury scores, VA, SSA, and LA were similar among the control and radiated groups. Neointimal formation was significantly reduced after place ment of radioactive stents as compared to control in both the overlapped (0 .93 +/- 0.12 vs. 1.31 +/- 0.51 mm(2), p < 0.05) and nonoverlapped segments (1.14 +/- 0.21 vs. 1.91 +/- 1.04 mm(2), p < 0.05). The smooth muscle cell i ndex in the neointima was reduced. Intimal fibrin was increased in the radi ated group as compared to the control (p < 0.01 respectively). Conclusions: P-32 radioactive stents may be safe and effective in reducing neointimal formation leading to in-stent restenosis. Longer follow-up will be required to examine whether these positive findings can be maintained. ( C) 2001 Elsevier Science Inc.