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In this paper the structure and dynamics of the flow in the left heart ventricle are studied for different pumping efficiencies and mitral valve types (natural, biological and mechanical prosthetic).
The problem is investigated by direct numerical simulation of the Navier-Stokes equations, with
fluid/structure interaction for the ventricle and mitral valve dynamics. The solver is preliminarily validated by comparisons with ad hoc experiments and then used for production runs. It is found that the left ventricular flow is heavily affected by the specific type of the mitral valve and the effects are more pronounced for ventricles with reduced pumping efficiency. More in details, when the ejection fraction of the ventricle (ratio of the ejected fluid volume and maximum ventricle volume over the cycle) is within the physiological range (50-70%), regardless of the mitral valve geometry, the mitral jet sweeps the inner ventricle surface up to the apex thus preventing the undesired flow stagnation.
In contrast, for pathological ejection fractions (≤ 40%) the flow disturbances introduced by the prosthetic devices reduce the penetration capability of the mitral jet and weaken the recirculation in the ventricular apex. This is especially true for the bileaflet mechanical valve, whose disturbances on the mitral flow are the strongest and a region of stagnant fluid is produced. These findings have important clinical implications on the choice of the prosthetic devices in patients that need mitral valve replacement.
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