In-Vitro Assessment of the Effects of Transcatheter Aortic Valve Leaflet Design on Neo-Sinus Geometry and Flow

Abstract

Transcatheter aortic valve (TAV) leaflet thrombosis is a clinical risk with potentially fatal consequences. Studies have identified neo-sinus flow stasis as a cause of leaflet thrombosis. Flow stasis is influenced by the TAV leaflets, which affect the local fluid dynamics in the aortic sinus and neo-sinus. This study evaluated the effects of TAV leaflet features on the neo-sinus flow as a measure of leaflet thrombosis risk. Five TAVs of varied leaflet length and insertion height were tested in a simulator. Hydrodynamics and leaflet kinematics through en-phase imaging were quantified. Velocity fields were assessed using high-speed particle image velocimetry. Regions of flow stasis and particle residence times (PRTs) were quantified. TAVs with shorter leaflet length exhibited larger orifice areas and lower transvalvular pressure gradients. Shorter leaflet length and increased leaflet insertion TAVs additionally exhibited lower neo-sinus PRTs (0.44 ± 0.21 vs 2.83 ± 0.48 cycles, p<0.05) and higher neo-sinus peak velocities (0.15 ± 0.009 vs 0.07 ± 0.005m/s, p<0.05) than TAVs with longer leaflet length and lower leaflet insertion. The average neo-sinus volume positively correlated with PRT(r=0.810, p<0.001), and extent of flow stasis (r=0.682, p<0.05). These results suggest that a small neo-sinus volume may reduce flow stagnation and particle residence, potentially reducing the risk of leaflet thrombosis. We propose that leaflet design features might be proactively controlled in the design of future transcatheter aortic valves.