Low-energy γ-emitting stents inhibit intimal hyperplasia with minimal “edge effects” in a pig coronary artery model

PurposeThe objective of this study was to determine the effects of different doses of γ-emitting radioactive stents on intimal hyperplasia in a porcine coronary stent model at 28 days.MethodsSixty-four bare stents and those coated with palladium-103 [activities of 0 (control), 0.5, 1.0, 2.0, and 4.0 mCi] were implanted in the coronary arteries of 32 pigs. Stented segments were evaluated by histomorphometry at 28 days.ResultsThere was significantly more intima in the 0.5- and 1-mCi stents than in controls (4.27±0.52 and 4.71±1.13 vs. 1.71±0.61 mm2; P<.0001). Neointimal formation in 2-mCi stents was similar to that in controls, while that in 4-mCi stents was reduced compared to that in controls (2.34±1.61 and 0.82±0.25 vs. 1.71±0.61 mm2; P=NS and P<.05, respectively). Stent margin neointimal response was representative of that within the stent body, with nonsignficant modest increases in intimal area at adjacent nonstented segments in radioactive stent groups. There was a dose-dependent increase in inflammation scores. Radioactive stents had lower intimal smooth muscle and higher fibrin scores. There was an increase in adventitial fibrosis in 1- and 2-mCi stents versus controls (1.26±0.99, and 2.25±1.27 vs. 0.21±0.31; P<.001).ConclusionDose–response inhibition of in-stent hyperplasia with minimal “edge effects” occurs with low-energy γ-emitting stents. An increased inflammatory response at higher doses in palladium-103 stents indicates that later follow-up studies are necessary.