Efficacy and Safety of Absorbable Metallic Stents with Adjunct Intracoronary Beta Radiation in Porcine Coronary Arteries

Abstract

Absorbable metallic stents (AMS) utilizing Mg alloy carry advantages over permanent metallic stents because of their potential to eliminate stent thrombosis, chronic inflammation, or artifacts with noninvasive imaging. These stents, however, are associated with a modest degree of late recoil and intimal hyperplasia. The aim of the study was to test whether adjunct vascular brachytherapy (VBT) compared to AMS alone can overcome these limitations. Juvenile domestic pig coronary arteries underwent implantation of either AMS (n = 11) with prior adjunct VBT utilizing Sr/Y-90 beta source seeds, with a dose of 24 Gy at 2 mm from the source, or AMS alone (n = 11). At 28 days following intravascular ultrasound, vessels were harvested and analyzed by histomorphometry. Intravascular ultrasound analysis indicated that at follow-up, though statistically not significant, lumen and stent areas in the segments deployed with AMS following radiation were larger than those deployed with AMS alone (3.94 +/- 1.38 and 3.53 +/- 1.75 vs. 2.99 +/- 1.05 and 3.58 +/- 1.48). Extrastent plaque and intrastent plaque areas in the same segments were smaller (2.76 +/- 0.82 and 0.24 +/- 0.47 vs. 3.25 +/- 1.94 and 0.58 +/- 0.81). Morphometric data indicate that vessels in the VBT + AMS group showed characteristics of delayed healing and re-endothelialization. Neointimal area was significantly lower in the VBT + AMS group (0.49 +/- 0.34) compared to AMS (1.3 +/- 0.62, P = 0.001). Lumen area of the VBT + AMS was larger when compared with AMS alone (2.49 +/- 0.82 vs. 1.75 +/- 0.51, P = 0.02). VBT as an adjunct to AMS further reduces the intimal hyperplasia and improves the lumen area when compared to AMS alone but does not have any impact on late recoil.