Reduction of intimal hyperplasia with Re-188-labeled stents in a rabbit model at 7 and 26 weeks: an experimental study.

The aim of this study was to analyze the feasibility of (188)Re-labeled stents to reduce neointimal formation in a rabbit atherosclerosis model and to test the long-term effects at 7 and 26 weeks. Fifty-nine male New Zealand White rabbits were fed a 0.5% cholesterol diet for 4 weeks before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were sacrificed 7 and 26 weeks after stent implantation. Control stents were compared with (188)Re stents: (dose 1) 11.3 +/- 1.8 MBq; (dose 2) 37.3 +/- 4.2 MBq, and (dose 3) 80.1 +/- 7.8 MBq. Each activity group consisted of a short-term (7 weeks) and a long-term group (26 weeks), resulting in a total of eight study groups. No thrombotic occlusion was observed. The neointimal formation in the control group was 2.11 [95% confidence interval (CI): 0.68--6.52] mm(2) at 7 weeks and 2.10 (0.62--7.11) at 26 weeks. In the treatment groups, neointima reduction was detectable at 7 weeks [dose 1: 0.33 (0.09--1.22) mm(2); dose 2: 0.17 (0.05--0.57) mm(2); dose 3: 0.03 (0.01--0.13) mm(2)]. After 26 weeks, a catch-up of neointimal formation in the radioactive groups was most obvious in the low-dose group [dose 1: 0.80 (0.28--2.29) mm(2); dose 2: 0.18([0.06--0.52) mm(2); dose 3: 0.50 (0.17--1.42) mm(2)]. Compared to the long-term control group, neointimal reduction was still >60%. No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed re-endothelialization. (188)Re stents were capable to reduce intimal hyperplasia and did not cause thrombosis. The edge effect, which was the major limitation of (32)P stents, was not observed in (188)Re stents.