Highly resolved pulsatile flows through prosthetic heart valves using the entropic lattice-Boltzmann method

Abstract

Prosthetic heart valves have been widely used to replace diseased or defective native heart valves. Flow through bileaflet mechanical heart valves (BMHVs) have previously demonstrated complex phenomena in the vicinity of the valve owing to the presence of two rigid leaflets. This study aims to accurately capture the complex flow dynamics for pulsatile flow through a 23 mm St Jude Medical (SJM) Regent TM BMHV. The lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through the valve with the inclusion of reverse leakage flow at very high spatiotemporal resolution that can capture fine details in the pulsatile BMHV flow field. For higher-Reynolds-number flows, this high spatiotemporal resolution captures features that have not been observed in previous coarse resolution studies. In addition, the simulations are able to capture with detail the features of leaflet closing and the asymmetric b-datum leakage jet during mid-diastole. Novel flow physics are visualized and discussed along with quantification of turbulent features of this flow, which is made possible by this parallelized numerical method.

Blood Damage Through a Bileaflet Mechanical Heart Valve: A Quantitative Computational Study Using a Multiscale Suspension Flow Solver

“…The platelets that flow through the b-datum leakage jet experience higher instantaneous damage for a longer period of time. This higher damage after leakage is possibly made worse by the asymmetric leakage jets in the diastolic phase as observed in a previous study [33]. The con tinuous interaction of the b-datum jet with larger vortices on the ventricular side may explain the higher damage experienced by platelets in b-datum leakage flows.…”

“…17(c)), explaining why these platelets experience 1.76 times more accumulated damage than platelets flowing through valve housing gaps. It has also been shown that the fluid shear stresses at the b-datum jet are consistently higher (80-130 dynes/cm2) than those at the valve housing gaps (10-20 dynes/cm2) throughout the mid-diastolic phase [33].…”

“…The majority of platelets (68.9%) remain on the aortic side of the leaflets after 320 ms of F ig . 1 s tr a tin g (a ) p la te le t c a u g h t in r e c irc u la tio n n e a r s in u s e x p a n s io n w a ll, ( b ) c o rr e s p o n d in g v o r tic ity fie ld , (c ) v is c o u s s h e a r s tre s s fie ld (u n its in d y n e s /c n r ) , a n d (d ) d a m a g e a c c u m u la tio n o v e r tim e mid-diastole, most flow throughout the domain shows low vortic ity and slow recirculation [33]. Of interest is flow near the valve, where leakage flow past the closed leaflets in the valve may cause high platelet damage.…”

“…The numerical method is previously vali dated for quantifying platelet damage [30], and the use of realistic platelet modeling was shown to differ in blood damage assessment from point particle methods [31]. This numerical method has also been shown to resolve the smallest scales of BMHV fluid motion [32,33]. Thus, this study aims to model blood damage in BMHV flows with the highest spatiotemporal accuracy to date.…”

“…The hinge regions cannot be resolved at this spatial resolution. However, this high resolution is adequate to resolve the smallest Kolmogorov scales of turbulent fluid motion for this BMHV flow [32,33], Although the hinge gap regions are important in completely studying BMHV flows, this was not the focus of this particular study. The very high temporal resolution also resolves the Kolmogorov time scales.…”