Numerical simulation of mechanical mitral heart valve closure

A computational fluid dynamic simulation of a mechanical heart valve closin g dynamics in the mitral position was performed in order to delineate the f luid induced stresses in the closing phase. The pressure and shear stress f ields in the clearance region and near the inflow (atrial) side of the valv e were computed during the mitral heart valve closure. Three separate numer ical simulations were performed. The atrial chamber pressure was assumed to be zero in all the simulations. The first simulation was steady flow throu gh a closed mitral valve with a ventricular pressure of 100 mmHg (1.3 kPa). In the second simulation, the leaflet remained in the closed position whil e the ventricular pressure increased from 0 to 100 mm Hg at a rate of 2000 min Hg/s (simulating leaflet closure by gravity before the ventricular pres sure rise - gravity closure). In the third case, the leaflet motion from th e fully open position to the fully closed position was simulated for the sa me ventricular pressure rise (simulating the normal closure of the mechanic al valve). Normal closure (including leaflet motion towards closure, and su dden stop in the closed position) resulted in a relatively large negative p ressure transient which was not present in the gravity closure simulation. The wall shear stresses near the housing and the leaflet edge close to the inflow side were around 4000 Pa with normal closure compared to about 725 P a with gravity closure. The large negative pressure transients and signific ant increase in wall shear stresses due to the simulation of normal closure of the mechanical valve is consistent with the previously reported increas ed blood damage during the closing phase.