Effect of Aortic Annulus Size and Prosthesis Oversizing on the Hemodynamics and Leaflet Bending Stress of Transcatheter Valves: An In Vitro Study

Abstract

BackgroundThere are few data about the patient- and prosthesis-related factors influencing the hemodynamics of transcatheter heart valves (THVs). The objective of this in vitro study was to assess the effect of aortic annulus size and prosthesis oversizing on the valve hemodynamics and estimated leaflet bending stress of the Edwards SAPIEN balloon-expandable THV (Edwards Lifesciences, Irvine, CA). MethodsThe effective orifice area (EOA) of the 23-mm and 26-mm SAPIEN THVs were measured by Doppler echocardiography in a pulse duplicator under the following experimental conditions: (1) stroke volume of 20, 30, 50, 70, and 80 mL and (2) aortic annulus size of 19, 20, 21, and 22 mm for the 23-mm SAPIEN and 22, 23, and 24, and 25 mm for the 26-mm SAPIEN. The percentage of valve oversizing was calculated as follows: % OS = 100 × [(prosthesis nominal area − aortic annulus area)/aortic annulus area], where % OS is the percentage of oversizing. The leaflet bending stress was measured by high-speed camera imaging of the THV leaflet opening. ResultsThe 2 independent determinants of valve EOA were the aortic annulus diameter (R2 = 0.33; P < 0.001) and the stroke volume (R2 = 0.63; P < 0.001). The prosthesis size and % OS were not independently related to EOA. However, a larger % OS was independently associated with higher peak systolic leaflet bending stress (ΔR2 = 0.11; P < 0.0001). ConclusionsThe hemodynamic performance of THV is in large part determined by the aortic annulus diameter in which the valve is deployed. Oversizing (up to 20% in area) has no significant effect on valve EOA but is associated with higher leaflet bending stress, which might promote faster structural valve degeneration in the long term.