Comprehensive mechanical performance characteristics of newly developed ultra-thin coronary stents

Abstract

Endovascular technologies such as percutaneous transluminal coronary angioplasty and stenting are widely used due to being minimally invasive procedures. One of the endovascular devices, a drug-eluting stent (DES), proved to be a safe and effective therapeutic option for cardiologists, substantially reducing in-stent restenosis (ISR) rates. DES consists of thin (< 200 µm) or ultra-thin (< 70 µm) struts made of Cobalt-Chromium (CoCr) or other alloys. The DES with ultra-thin struts exhibits higher longitudinal flexibility and improved trackability. It also reduces vascular injury and promotes more rapid endothelization, substantially decreasing the risk of ISR. This study evaluates comprehensive mechanical performances of two different structural designs of newly developed ultra-thin CoCr stents (i.e., strut width of 75 µm or 65 µm). These two stent designs are engineered with distinct bridge size and distribution patterns, prioritizing enhanced flexibility irrespective of the strut thickness. Computational modeling results show anticipated stress distribution with maximum local stresses, which are compared with experimental outcomes conducted in this study. ASTM guideline based in vitro experimental studies have been conducted to assess the stents’ longitudinal flexibility, radial strength, recoil and shortening, as well as crushability through this study. Three-point bending experiments have demonstrated that the stent design 1 requires less bending force compared to the design 2, showing better longitudinal flexibility of the stent design 1 in the collapsed state for the new ultra-thin DES devices. The design 1 also showed superior radial strength and recoiling phenomena, as well as smaller shortening. In short, the stent design 1 shows better mechanical performance needed for the coronary artery DES.