Abstract 17991: Angulation Range of Coronary Artery During the Cardiac Cycles is a Key Factor Inducing Stent Fracture; Demonstration by an in vitro Accelerated Durability Test

Abstract

Introduction: Stent fracture (SF) is recognized as one of the unsolved issues inducing restenosis or thrombosis. Hinge motion has been identified as a predictor of SF. The aim of this study is to elucidate SF probability of current drug eluting stents (DESs) against angulation ranges during the cardiac cycles, utilizing an in vitro accelerated durability tester. Methods: A cyclic-bend accelerated durability tester we have developed was used. Stents were deployed in elastic bend-artery replicas those mechanical stiffness was adjusted to that of referenced human coronary artery (stiffness parameter β=30±2). Three-link L605 CoCr stent (Xience Prime, Abbott Vascular), 2-link MP35N CoCr stent (Resolute Integrity, Medtronic), and 2-link PtCr stent (Promus Element, Boston Scientific) were chosen as test subjects. Influences of magnitude of angulation ranges on incidences of SF were investigated under the following bend conditions from 130 to 100 degrees (angular difference during the cycle (AD): 30 degrees), from 130 to 90 degrees (AD: 40 degrees), and from 130 to 80 degrees (AD: 50 degrees), respectively. Under each bend condition, three samples for each stent were tested for 1.0х10 8 cycles at 20Hz, those duration is equivalent to 2.5 years in vivo. Results: Under the AD of 30 degrees, multiple and single strut fracture were observed for each one of three L605 CoCr and MP35N CoCr stents, whereas no fracture was observed for PtCr stents. Under the severer ADs of 40 degrees and 50 degrees, all the three L605 CoCr and MP35N CoCr stents were multiply fractured, whereas PtCr stents had one single-strut-fracture and two multiple-strut-fractures among each three stents under the above conditions. These data indicated that PtCr stent platform has higher resistance to SF among wide ranges of cyclic-bend angulations. The total numbers of stent strut fractures of L605 CoCr, MP35N CoCr, and PtCr stents were 3, 1, 0 in the AD of 30 degrees, 20, 8, 1 in the AD of 40 degrees, and 18, 13, 4 in the AD of 50 degrees. Links were frequent sites of SF for CoCr stents, whereas crowns were those for PtCr stents. Conclusions: This study elucidated differences in fracture resistance against cyclic angulation ranges during the cardiac cycles and the critical angulation ramges for current three DESs.