A Novel Ex Vivo Model of Unbalanced Common Atrioventricular Valve: Insights into Biomechanics and Hemodynamics During Single Ventricle Palliation.

Abstract

To investigate biomechanics and failure mechanisms of unbalanced right-dominant common atrioventricular valves (CAVVs) across stages of single ventricle palliation (SVP). A patient-specific adjustable valve testing mount was developed and size-matched porcine tricuspid and mitral valves were combined to construct CAVVs (n=5). Valves were tested in a heart simulator under hemodynamic conditions replicating Norwood, Glenn and Fontan physiologies. Papillary muscles were displaced vertically and horizontally to simulate chordal prolapse, shortening, and ventricular dilatation. Strain sensors configured as neochordae quantified leaflet force profiles. Bridging leaflets experienced higher peak and mean forces than mural leaflets (p<0.05), correlating with larger leaflet surface area. Regurgitant fraction (RF) increased with all geometric perturbations (p<0.001), with greater rate of increase during chordal prolapse than shortening. Forces were higher in 5mm chordal prolapse compared to baseline. Forces decreased in 5mm chordal shortening and ventricular dilatations as RF increased. Peak leaflet forces and average yank were highest under Norwood conditions (p<0.05), whereas mean forces were greatest during Fontan physiology (p<0.01). Although RF increased with geometric changes at all SVP stages, the relative increase over baseline was greatest during Norwood (p<0.05). Stage-dependent loading conditions and ventricular geometry critically determine CAVV biomechanics and failure during SVP. Glenn offloading reduces peak leaflet forces and improves valve performance, whereas Fontan afterload increases mean leaflet stress, potentially accelerating long-term failure. Ventricular geometric perturbations exert the greatest adverse effect during Norwood, conferring the highest risk of valve dysfunction.