Biomechanical analysis of cuffed distal end-to-side anastomosis of bypass grafts and design optimization.

摘要

Arterial bypass grafts, the major treatment for arterial stenosis, have long-term patencies limited by intimal hyperplasia (IH), especially at the distal end-to-side anastomosis. Use of the Miller's cuff, a piece of vein interposed between the synthetic graft and the host artery has shown an increased patency over conventional anastomoses. A previous chronic porcine experiment has shown a reduced amount of IH in a venous cuffed anastomosis relative to that in an ePTFE cuffed anastomosis, both constructed with the same initial geometry. Since mechanical factors are thought to influence the vascular remodeling process, a computational biomechanical analysis was performed in order to find the mechanism behind the reduced IH in the venous cuff. Few prior studies have used the more realistic, large strain models for wall stress analysis and optimizations to reduce IH have only considered hemodynamic factors present in the physiologically loaded anastomotic geometry.; In this study, a unique hyperelastic finite element and a pulsatile computational fluid dynamic simulation were performed to compare the mechanical environments in the ePTFE and venous Miller's cuff distal end-to-side anastomoses. Transport of nitric oxide released from the venous cuff was also simulated. A multiple regression analysis was performed between these factors and the histological data. An optimized design was developed based on the results of the regression analysis.; The study showed that: (1) the ePTFE and venous cuffs deformed differently under physiological loading with increased strain distribution along the artery floor in the latter, (2) wall strain and oscillatory shear index (OSI) contribute to IH proportionally and equivalently in the ePTFE cuff, and (3) mechanical factors alone do not account for the reduced IH in the venous cuff, suggesting the involvement of some biological factor. Based on the biomechanical simulation, three configurations have been proposed to optimize the anastomotic design.; Future work includes: (1) identification of the specific biological factor that inhibits IH in the venous cuff and (2) characterization of the mechanics for the bypass graft in a more sophisticated way, such as including structure and fluid interaction.