Abstract
In this paper, the structure and the 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, two-way coupled with a structural solver for the ventricle and mitral valve dynamics. The whole solver is preliminarily validated by comparisons with ad hoc experiments. It is found that the system works in a highly synergistic way and the left ventricular flow is heavily affected by the specific type of mitral valve, with effects that are more pronounced for ventricles with reduced pumping efficiency. When the ventricle ejection fraction (ratio of the ejected fluid volume to 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 undesired flow stagnation. In contrast, for pathological ejection fractions (⩽40 %), the flow disturbances introduced by the bileaflet mechanical valve reduce the penetration capability of the mitral jet and weaken the recirculation in the ventricular apex. Although in clinical practice the fatality rates in the five-year follow-ups for mechanical and biological mitral valve replacements are essentially the same, a breakdown of the deaths shows that the causes are very different for the two classes of prostheses and the present findings are consistent with the clinical data. This might have important clinical implications for the choice of prosthetic device in patients needing mitral valve replacement.
Highlights
The human heart is made of two separate volumetric pumps, the right and the left, shaded in blue and red respectively in figure 1
It is found that the system works in a highly synergistic way and the left ventricular flow is heavily affected by the specific type of mitral valve, with effects that are more pronounced for ventricles with reduced pumping efficiency
Since in this paper we aim to study the flow changes induced by different mitral valves, it is crucial to separate the effects of the deliberately modified geometry from those of the less known material properties
Summary
The human heart is made of two separate volumetric pumps, the right and the left, shaded in blue and red respectively in figure 1. The aim of the present study is to investigate how the flow structure inside the left ventricle is altered by a mitral valve replacement for different volume fractions ejected by the left ventricle. This requires the simultaneous consideration of different prosthetic valve models (figure 2) and various levels of ventricle pumping efficiency. In order to fill this gap and to simulate the complete system with the minimum number of assumptions, in this paper, a full fluid–structure interaction (FSI) model for the left ventricle and the mitral valve is used, obtaining a more realistic representation of the phenomenon In this way, both the valve and the ventricle dynamics are determined by their interaction with the flow, which, in turn, depends on the motion of the boundaries. Closing remarks and perspectives for future studies are given in the final section
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
