Abstract 17943: Biomechanical Finite Element Analysis of Asymmetric Bicuspid Aortic Valve With Different Commissure Positionings for Repair

Abstract

Introduction: While bicuspid aortic valves (BAVs) exist with a wide variety of phenotypes, type 1 valves that require surgery often present with varying levels of cusp fusion, raphe geometry, and commissure positioning angles. Regarding central coaptation angle, BAVs commonly present with asymmetry between fused and non-fused cusps, and surgical debate focuses on whether BAV repair should aim to minimize or accommodate for this asymmetry. We aimed to compare the hemostatic structural integrity of different commissure positionings for repair based on a BAV with an original 150° central angle. Methods: BAV models were designed based on literature of asymmetric valve geometry. The central angle of the pathological valve was 150°, which is common (Fig A). Two subsequent valve geometries were modeled to represent the repair conditions where commissure positioning forces result in central angles of 165° (Fig B) and 180° (Fig C). These models were matched with leaflet surface area and implemented with mechanical parameters of aortic leaflet tissues. Coaptation planes were modeled as encastre boundaries. A hemostatic pressure gradient was applied at 90 mmHg to mimic peak diastolic pressures, and Fusion360 was used for finite element simulations. Results: All three models showed maximum von Mises stresses in the belly regions of the fused leaflet (Fig A-C). Upon running the simulations, the 150° model showed maximum Von Mises stresses of 8103 Pa, the 165° model showed maximum stresses of 5405 Pa, and the 180° model showed stresses of 6116 Pa. Conclusions: By leveraging finite element models and computational biomechanics analyses, we were able to identify differences in BAV leaflet stresses based on alternate commissural positioning of an asymmetric BAV phenotype. Our finding suggests that peak diastolic leaflet forces may be minimized by focusing surgical BAV repair on a moderate reduction of leaflet asymmetry (i.e., 150° to 165°), without imposing perfect symmetry.