BACKGROUND: Radioactive stents have been reported to reduce in-stent neointimal thickening. An unexpected increase in neointimal response was observed, however, at the stent-to-artery transitions, the so-called "edge effect." To investigate the factors involved in this edge effect, we studied stents with 1 radioactive half and 1 regular nonradioactive half, thereby creating a midstent radioactive dose-falloff zone next to a nonradioactive stent-artery transition at one side and a radioactive stent-artery transition at the other side. METHODS AND RESULTS: Half-radioactive stents (n=20) and nonradioactive control stents (n=10) were implanted in the coronary arteries of Yucatan micropigs. Animals received aspirin and clopidogrel as antithrombotics. After 4 weeks, a significant midstent stenosis was observed by angiography in the half-radioactive stents. Two animals died suddenly because of coronary occlusion at this mid zone at 8 and 10 weeks. At 12-week follow-up angiography, intravascular ultrasound and histomorphometry showed a significant neointimal thickening at the midstent dose-falloff zone of the half-radioactive stents, but not at the stent-to-artery transitions at both extremities. Such a midstent response (mean angiographic late loss 1.0 mm) was not observed in the nonradioactive stents (mean loss 0.4 to 0.6 mm; P< 0.01). CONCLUSIONS: The edge effect of high-dose radioactive stents in porcine coronary arteries is associated with the combination of stent injury and radioactive dose falloff.

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Keywords Animals, Blood Vessel Prosthesis Implantation, Coronary Angiography, Coronary Vessels/pathology/*radiation effects/surgery, Disease Models, Animal, Disease Progression, Dose-Response Relationship, Radiation, Drug Implants, Female, Graft Occlusion, Vascular/*etiology/pathology/*prevention & control, Implants, Experimental, Phosphorus Radioisotopes/*administration & dosage, Research Support, Non-U.S. Gov't, Stents/*adverse effects, Swine, Miniature, Tunica Intima/pathology/radiation effects, Vascular Patency/radiation effects, angioplasty, radioisotopes, restenosis, stents
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Journal Circulation (Baltimore)
van der Giessen, W.J, Harteveld, M.S, Coen, V.L.M.A, Bhagwandien, R.E, Au, A, Ligthart, J.M.R, … Boersma, H. (2001). "Edge Effect" of 32P Radioactive Stents Is Caused by the Combination of Chronic Stent Injury and Radioactive Dose Falloff. Circulation (Baltimore), 104(18), 2236–2241. doi:10.1161/hc4301.097873