Abstract 13307: Neointimal Coverage Reduces a Potential Risk of Stent Separation of Sirolimus Eluting Stent: Accelerated Durability Tests Under in-vivo Simulated Cyclically-Bended Proximal Right Coronary Artery Environment
Introduction: High incidence of stent fracture is reported in sirolimus eluting stent (SES). However, despite the identical stent platform with 316L stainless steal, little has been reported about fracture incidence in its bare metal stent era. We aimed to assess influence of neointimal uncoverage of SES on potential risk of stent separation, using an accelerated durability tester simulating in-vivo cyclically-bended proximal right coronary artery (RCA) environment.
Methods: From bend-angles of RCA in end-systole and end-diastole of 63 patients, the data classified in type-B according to ACC/AHA guideline were used. Because the average angles in end-systole and end-diastole were 105° and 125°, a RCA replica with bend-angle of 125° was fabricated. Mechanical stiffness of the replica was adjusted to that of referenced human coronary arteries. In the accelerated durability tests, the RCA replica was cyclically bended from 125° to 105°. SESs (3.0mm×18mm) were deployed in the replicas at nominal pressure (n=12). Luminal surfaces of 6 stents were covered with elastic silicone with a thickness of 200µm, mimicking an environment by neointimal coverage. Bend-load was exerted 1200 cycles per minute to the stent in the RCA replica filled with 37°C-controlled phosphate buffered saline. Cycles to fracture in the durability tests were transformed into corresponding days at 70 beats per minute. All the tests were conducted for 2 years equivalent except for incidence of stent-separation.
Results: All SESs without neointimal coverage model were completely separated in 11.6 ± 6.9 days (n=6). Strut fracture was initiated in 7.6 ± 6.7 days (n=6), mainly at the inner side of the bended curvature. However, In SESs with neointimal coverage model, only one stent was completely separated in 350 days, and five stents were not separated until 2 years. Strut fracture was initiated in 2.8± 2.4 days (n=6). These data suggested that neointimal coverage had strong impact on reduction of potential risk of stent separation. Engineering analysis revealed that bending moment exerted to SESs without neointimal coverage increased due to incomplete apposition to the bended replicas.
Conclusions: This study revealed that neointimal coverage of SESs reduces a potential risk of stent separation.
- © 2011 by American Heart Association, Inc.