Experimental investigation of the flow downstream of a dysfunctional bileaflet mechanical aortic valve

Abstract

Mechanical heart valve replacement is the preferred alternative in younger patients with severe symptomatic aortic valve disease. However, thrombus and pannus formations are common complications associated with bileaflet mechanical heart valves.This leads to risks of valve leaflet dysfunction, a life-threatening event. In this experimental study, we investigate, using time-resolved planar particle image velocimetry, the flow characteristics in the ascending aorta in the presence of a dysfunctional bileaflet mechanical heart valve. Several configurations of leaflet dysfunction are investigated and the induced flow disturbances in terms of velocity fields, viscous energy dissipation, wall shear stress, and accumulation of viscous shear stresses are evaluated. We also explore the ability of a new set of parameters, solely based on the analysis of the normalized axial velocity profiles in the ascending aorta, to detect bileaflet mechanical heart valve dysfunction and differentiate between the different configurations tested in this study. Our results show that a bileaflet mechanical heart valve dysfunction leads to a complex spectrum of flow disturbances with each flow characteristic evaluated having its own worst case scenario in terms of dysfunction configuration. We also show that the suggested approach based on the analysis of the normalized axial velocity profiles in the ascending aorta has the potential to clearly discriminate not only between normal and dysfunctional bilealfet heart valves but also between the different leaflet dysfunction configurations. This approach could be easily implemented using phase-contrast MRI to follow up patients with bileaflet mechanical heart valves. K E Y W O R D Sbileaflet mechanical heart valve, flow dynamics, shear stress accumulation, valve dysfunction, viscous energy dissipation E250 | DARWISH et Al.

Computational hemodynamic investigation of a new bileaflet mechanical heart valve

“…The axial velocity pattern that develops downstream of the valve (Figures 6 and 7) is qualitatively comparable with that reported by De Vita et al 35 and Darwish et al 39 The overall flow physics predicted are similar to the results reported and discussed by Darwish et al, 39 who performed experiments for pulsatile flows in Saint-Jude BMHVs.…”

“…Further, viewing WSS profiles for both models of blood, it is seen that low and oscillating WSS occurs in the wall of the valve, particularly in the sinus of Valsalva, and hence this region is susceptible to atherogenesis. 39,43,44 Obviously the WSS of the non-Newtonian flow is higher than that of the Newtonian flow due to the shear-thinning effect of blood. The negative values in WSS indicate flow recirculation and stagnation.…”

Hemodynamic Performance of Dysfunctional Prosthetic Heart Valve with the Concomitant Presence of Subaortic Stenosis: In Silico Study

“…For the isolated 100% leaflet dysfunction at different flow rates, the Vpeak value increased from 0.84 m/s to 1.94 m/s (127% increase), and the TPGmean value increased from 1.42 mmHg to 6.47 mmHg (350% increase). Moreover, the DVI and EOA were shown to be the less flow-dependent parameters [ 19 , 36 ].…”

“…Using cardiac simulators, a set of in vitro studies investigated blood flow behavior downstream of BMHV in terms of level of turbulence, shear stress, and coherent structure. Clinically related echo Doppler parameters, such as EOA and Transvalvular pressure gradient, were also explored [ 33 , 34 , 35 , 36 ].…”

Artificial Organs 2019: A year in review

“…Ahmed Darwish et al of Concordia University, Montreal, Canada reported on the flow downstream of a dysfunctional bileaflet mechanical aortic valve. Several configurations of leaflet dysfunction were investigated and the induced flow disturbances in terms of velocity fields, viscous energy dissipation, wall shear stress, and accumulation of viscous shear stresses.…”