"Edge Effect" of (32)p radioactive stents is caused by the combination of chronic stent injury and radioactive dose falloff.
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.


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.
van Der Giessen
W J
WJ
Department of Cardiology, Thoraxcenter, Erasmus Medical Center, Rotterdam, the Netherlands. vandergiessen@card.azr.nl
Regar
E
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Harteveld
M S
MS
Coen
V L
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Bhagwandien
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Au
A
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Levendag
P C
PC
Ligthart
J
J
Serruys
P W
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den Boer
A
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Verdouw
P D
PD
Boersma
E
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Hu
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van Beusekom
H M
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D000818:Animals; D019917:Blood Vessel Prosthesis Implantation; D017023:Coronary Angiography; D003331:Coronary Vessels / Q000473:pathology / Q000528:radiation effects* / Q000601:surgery; D004195:Disease Models, Animal; D018450:Disease Progression; D004307:Dose-Response Relationship, Radiation; D004343:Drug Implants; D005260:Female; D006083:Graft Occlusion, Vascular / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control*; D020007:Implants, Experimental; D010761:Phosphorus Radioisotopes / Q000008:administration & dosage*; D015607:Stents / Q000009:adverse effects*; D013556:Swine, Miniature; D017539:Tunica Intima / Q000473:pathology / Q000528:radiation effects; D014654:Vascular Patency / Q000528:radiation effects
D004343:Drug Implants; D010761:Phosphorus Radioisotopes