Vasomotor Function Comparative Assessment at 1 and 2 Years Following Implantation of the Absorb Everolimus-Eluting Bioresorbable Vascular Scaffold and the Xience V Everolimus-Eluting Metallic Stent in Porcine Coronary Arteries Insights From In Vivo Angiography, Ex Vivo Assessment, and Gene Analysis at the Stented/Scaffolded Segments and the Proximal and Distal Edges

OBJECTIVES The purpose of this study was to assess and compare in vivo the restoration of vasomotor function following Absorb bioresorbable vascular scaffold (BVS) (Abbott Vascular, Santa Clara, California) and metallic Xience V (XV) (Abbott Vascular, Santa Clara, California) stent implantations in porcine coronary arteries at 1 and 2 years. BACKGROUND Drug-eluting metallic coronary stents induce sustained vasomotor dysfunction, and preliminary observations from arteries with bioresorbable scaffolds have indicated partially restored vasoreactivity. METHODS A total of 15 Absorb BVS (3.0 x 18.0 mm) and 14 XV (3.0 x 18.0 mm or 3.0 x 12.0 mm) stents were randomly implanted in the main coronaries of 12 nonatherosclerotic swine. The effect of implant on vasomotor performance (constrictive and expansive) was measured in the stented/scaffolded segments and the 5-mm proximal and distal adjacent segments in vivo by angiography assessing mean luminal diameter changes following infusion of vasoactive agents at 1 year (n = 6) and 2 years (n = 6) as well as ex vivo at 2 years using a tissue chamber apparatus. Endothelial cell function and smooth muscle cell phenotype gene marker levels were evaluated with quantitative real-time polymerase chain reaction. RESULTS The scaffolded Absorb BVS segments showed fully restored constrictive response compared with XV implanted vessels at 1 year: -24.30 +/- 14.31% versus -1.79 +/- 6.57% (p < 0.004) and at 2 years: -28.13 +/- 14.60% versus -3.90 +/- 6.44% (p < 0.004). The early restoration of vasomotor function within the scaffolded segments reached a peak at 1 year and did not significantly change up to 2 years. The vasoactive responses of Absorb BVS-implanted vessels within the scaffolded segments were similar to those observed within the proximal and distal edge segments at both time points. Conversely, the stented XV segments demonstrated significantly impaired constrictive response compared with the distal XV edges at 1 year: -1.79 +/- 6.57% versus -21.89 +/- 7.17% (p < 0.0002) and at 2 years: -3.90 +/- 6.44% versus -21.93 +/- 15.60% (p < 0.03). Ex vivo assessment of contraction induced by PGF2a and relaxation induced by substance P of isolated BVS segments compared with XV-treated segments generated greater contraction force of 3.94 +/- 0.97 g versus 1.83 +/- 1.03 g (p < 0.05), and endothelial-dependent relaxation reached 35.91 +/- 24.74% versus 1.20 +/- 3.79% (p < 0.01). Quantitative real-time polymerase chain reaction gene analysis at 2 years demonstrated increased Connexin 43 messenger ribonucleic acid levels of Absorb BVS-treated vessels compared with XV-treated vessels: 1.92 +/- 0.23 versus 0.77 +/- 12 (p < 0.05). CONCLUSIONS Absorb BVS-implanted coronary arteries demonstrate early functional restoration of the scaffolded and adjacent segments at 1 year, which is preserved up to 2 years. (C) 2016 by the American College of Cardiology Foundation.