Effect of graft sizing in valve-sparing aortic root replacement for bicuspid aortic valve: The Goldilocks ratio

Abstract

Objective: To investigate the effect of graft sizing on valve performance in valve-sparing aortic root replacement for bicuspid aortic valve.

Methods: In addition to a diseased control model, 3 representative groups-free-edge length to aortic/graft diameter (FELAD) ratio <1.3, 1.5 to 1.64, and >1.7-were replicated in explanted porcine aortic roots (n = 3) using straight grafts sized respective to the native free-edge length. They were run on a validated ex vivo univentricular system under physiological parameters for 20 cycles. All groups were tested within the same aortic 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 compare outcomes across groups.

Results: The diseased control had mean transvalvular gradient 10.9 ± 6.30 mm Hg, regurgitation fraction 32.5 ± 4.91%, and orifice area 1.52 ± 0.12 cm². In ex vivo analysis, all repair groups had improved regurgitation compared with control (P < .001). FELAD <1.3 had the greatest amount of regurgitation among the repair groups (P < .001) and 1.5-1.64 the least (P < .001). FELAD <1.3 and >1.7 exhibited greater mean gradient compared with both control and 1.5 to 1.64 (P < .001). Among the repair groups, 1.5 to 1.64 had the largest orifice area, and >1.7 the smallest (P < .001).

Conclusions: For a symmetric bicuspid aortic valve, performance after valve-sparing aortic root replacement shows a bimodal distribution across graft size. As the FELAD ratio departs from 1.5 to 1.64 in either direction, significant increases in transvalvular gradient are observed. FELAD <1.3 may also result in suboptimal improvement of baseline regurgitation.

Keywords: David procedure; aortic root replacement; aortic valve repair; bicuspid aortic valve; free-edge length; graft size; valve-sparing aortic root replacement.

Graphical abstract

Free-edge length to graft size ratio of 1.5-1.64 results in lowest mean valve gradient.

Figure 1

On the basis of previous simulation work, 3 porcine aortic roots were bicuspidized and tested in validated univentricular simulator for 20 runs for valve-sparing root replacement with varying FELADs: <1.3, 1.5 to 1.64, and >1.7. The control model was based on a typical diseased bicuspid valve with mild-to-moderate regurgitation. All repair conditions were tested in the same root by the same operator to minimize inter-root differences. Graft size significantly affected valve function after repair, with a free-edge length to graft ratio of 1.5 to 1.64 exhibiting ideal performance in ex vivo assessment. FELAD, Free-edge length to aortic/graft diameter.

Figure 2

Valve regurgitation based on free-edge length to graft diameter ratio. ∗∗∗P < .001. All repair groups had significantly improved regurgitation compared with control. Pairwise comparison showed that the <1.3 group had significantly greater regurgitation than both the 1.5 to 1.64 and >1.7 groups. The 1.5 to 1.64 group had significantly lower regurgitation than the >1.7 group. Error bars denote standard error from linear mixed effects model.

Figure 3

Transvalvular gradient based on free-edge length to graft diameter ratio. ∗∗∗P < .001. Linear mixed effects modeling across repair groups showed significantly higher mean transvalvular gradient for the <1.3 and >1.7 groups compared with control, whereas the 1.5 to 1.64 group was not significantly different from control (P = .64). Pairwise comparisons confirmed these results and showed that the 1.5 to 1.64 group had significantly lower mean transvalvular gradient than both the <1.3 and >1.7 groups. Error bars denote standard error from linear mixed effects model.

Figure 4

Valve orifice area based on free-edge length to graft diameter ratio. ∗P < .05, ∗∗∗P < .001. All repair groups had significantly smaller orifice area compared with the control group. Pairwise comparison showed that the 1.5 to 1.64 group had significantly larger orifice area than the <1.3 and >1.7 groups, whereas the >1.7 group had significantly smaller orifice area than the <1.3 group. Error bars denote standard error from linear mixed effects model.