Effect of Graft Sizing in Valve-sparing Aortic Root Replacement for Bicuspid Aortic Valve: The Goldilocks Ratio

Objective: Valve-sparing aortic root replacement in the setting of native bicuspid aortic valve is a well-described technique. However, the optimal gross morphology of this repair as it relates to graft sizing has yet to be defined. This study builds on previous computational work and utilizes an ex-vivo approach to assess the relationship between graft size and valve function.
Methods: In previous work, our group modeled symmetric bicuspid valves with varying free-edge-length-to-aortic-diameter (FELAD) ratios via fluid-structure interaction simulations in a single patient-specific model geometry, with evidence of stenosis at values <1.3 and billowing at >1.71. Based on these results, three representative groups (FELAD <1.3, 1.5-1.64, >1.7) were replicated in explanted fetal porcine aortic roots (n=3) using straight grafts sized respective to the measured native free-edge length (Figure A). These valves were then run on a validated ex-vivo univentricular system under physiological parameters for 20 cycles for each condition (Figure B). All repair groups, in addition to the diseased bicuspid control model, were tested within the same root to minimize inter-root differences. Outcomes included transvalvular gradient, regurgitation fraction, and orifice area. Linear mixed effects model and pairwise comparisons were employed to evaluate differences in outcomes across groups.
Results: The diseased control model had mean transvalvular gradient 10.9 +/- 6.30 mm Hg, mean regurgitation fraction 32.5 +/- 4.91%, and mean orifice area 1.52 +/- 0.12 cm2. Ex-vivo analysis showed significantly higher transvalvular gradient for FELAD <1.3 and >1.7 compared to both control and 1.5-1.64 group (p<0.001, Figure C). Transvalvular gradient was not significantly different between <1.3 and >1.7 groups. All repair groups had significantly improved regurgitation compared to control (p<0.001). FELAD <1.3 had the highest amount of regurgitation among the repair groups (p<0.001), and 1.5-1.64 the least (p<0.001). Notably, all repair groups had significantly smaller orifice area compared to control (p<0.001 for <1.3 and >1.7, p=0.03 for 1.5-1.64). Among the repair groups, 1.5-1.64 had the largest orifice area, and >1.7 the smallest (p<0.001).
Conclusions: In the context of valve-sparing aortic root replacement for a regurgitant, symmetric bicuspid valve, there is a bimodal distribution for valve performance as it relates to graft sizing. As the FELAD ratio departs from 1.5-1.64 in either direction, although regurgitation improves, significant increases in transvalvular gradient are observed.

Perry Choi (1), Amit Sharir (1), Yoshikazu Ono (1), Masafumi Shibata (1), Alexander D. Kaiser (1), Yuanjia Zhu (1), Alison L. Marsden (1), Y. Joseph Woo (1), Michael Ma (1), Joon Bum Kim (1), (1) Stanford University, Stanford, CA

Perry Choi

Abstract Presenter

Dr. Perry Choi is a 4th year resident in Stanford's Integrated Cardiothoracic Surgery Residency Program. He received his MD at Harvard Medical School, where he spent time conducting research on mitral valve replacement options in the pediatric population under the mentorship of Dr. Sitaram Emani at Boston Children's Hospital. Currently, he is working as a research fellow in the labs of Dr. Michael Ma and Dr. Joseph Woo, investigating the biomechanics of ventricular remodeling and complex valvular repair techniques in congenital heart disease. His career interests include academic surgery, adult congenital cardiac disease, and surgical education.