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Valve thrombosis following transcatheter aortic valve replacement: significance of blood stasis on the leaflets

OBJECTIVES
Leaflet thrombosis following transcatheter aortic valve replacement (TAVR) and valve-in-valve (ViV) procedures has been increasingly recognized. However, the factors affecting the post-TAVR/ViV thrombosis are not fully understood. This study aimed to investigate the effect of the geometric confinement of transcatheter aortic valve (TAV) on blood residence time (BRT) on the TAV leaflets and in turn on the post-TAVR valve thrombosis.


METHODS
Two computational models, representing a surgical bioprosthesis and a TAV, were developed to study the effect of the geometric confinement on BRT on the leaflets in ViV setting/TAVR Intra-annular positioning. 3D flow fields were obtained via a one-way fluid-solid interaction modelling approach validated by experimental testing. BRT was compared between the two models by quantification and statistical analysis of the residence time of randomly distributed particles in close proximity of the leaflets.


RESULTS
Significantly longer BRT on the leaflets was observed in the TAV compared to the surgical valve during different stages of the cardiac cycle. During forward flow, the mean value of BRT was found to be 39% higher in the TAV compared to the surgical bioprosthesis ( P <  0.0001). During diastole, specifically from end-systole to mid-diastole and from mid-diastole to the beginning of systole, the amount by which the mean BRT was higher for TAV compared to the surgical valve was 150% and 40%, respectively ( P <  0.0005).


CONCLUSIONS
The geometric confinement of TAV by the failed bioprosthesis or the calcified native valve increases the BRT on the TAV leaflets. This may act as a permissive factor in valve thrombosis.