The “Edge Effect” After Implantation of β-Emitting (55Co) Stents with High Initial Activity

Abstract

The aim of this study was to evaluate the incidence and the cause of “edge restenosis” after implantation of high activity 41.1 μCi±1.2 μCi=1520 kBq±44 kBq, β-emitting (55Co) stents. Proton bombarding in cyclotron has brought the radioactivity. Intravascular ultrasound (IVUS) investigation has been completed in 10 patients. The angiographies performed at 6 month revealed restenosis >50 % in 5 cases (50 %). The analysis of edges (5 mm distally and proximally to the last stent struts) showed no significant changes in TVV (187.3±62.60 mm3 and 176.9±53.5 mm3) but PMV increase significantly (i.e. neointimal proliferation) from 61.9±31.2 mm3 to 82.2±43.4 mm3 (p<0.04) and was the major contributor (from 66 %) to lumen volume loss (125.4±40.7 mm3 and 94.7±22.2 mm3, p<0.02). In conclusion, neither statistically significant positive nor negative remodelling at the “stent edges“, were present. Statistically significant increase in plaque+media volume (i.e. neointimal hyperplasia) and reduction in lumen volume were found. The cause of “edge restenosis” was especially (from 66 %) due to increase in plaque+media volume (i.e. neointimal hyperplasia). Probably, main reason for “edge effect”/neointimal hyperplasia was in this trial sharp fall-off in radiation at the edges of the stents.