Vortices Formed on the Mitral Valve Tips Aid Normal Left Ventricular Filling

ArticleinAnnals of Biomedical Engineering 41(5) · February 2013with32 Reads
DOI: 10.1007/s10439-013-0755-0 · Source: PubMed
Abstract
For the left ventricle (LV) to function as an effective pump it must be able to fill from a low left atrial pressure. However, this ability is lost in patients with heart failure. We investigated LV filling by measuring the cardiac blood flow using 2D phase contrast magnetic resonance imaging and quantified the intraventricular pressure gradients and the strength and location of vortices. In normal subjects, blood flows towards the apex prior to the mitral valve opening, and the mitral annulus moves rapidly away after the valve opens, with both effects enhancing the vortex ring at the mitral valve tips. Instead of being a passive by-product of the process as was previously believed, this ring facilitates filling by reducing convective losses and enhancing the function of the LV as a suction pump. The virtual channel thus created by the vortices may help insure efficient mass transfer for the left atrium to the LV apex. Impairment of this mechanism contributes to diastolic dysfunction, with LV filling becoming dependent on left atrial pressure, which can lead to eventual heart failure. Better understanding of the mechanics of this progression may lead to more accurate diagnosis and treatment of this disease.
    • "Prior in vivo studies involving imaging techniques have established the fact that in a healthy heart, there exists a large asymmetric clockwise vortex located at the center of the LV during ventricular diastole [4, 8,[21][22][23]. This asymmetric clockwise vortex which fills nearly the entire LV during the interval between diastole and systole conserves kinetic energy of the blood as it is redirected from the mitral valve to the aorta [4]. "
    [Show abstract] [Hide abstract] ABSTRACT: Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve) has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation.
    Full-text · Article · Jun 2016
    • "There is ample of evidence pointing to a relationship between LV pathology and intraventricular flow patterns, notably the dynamics of the MVR (Hong et al. 2008, Carlhäll & Bolger 2010, Charonko et al. 2013, Mangual et al. 2013). The interaction of the MV leaflets and supporting structures with the blood flow, however, is so complex (Charonko et al. 2013) that a simple correlation among those factors is unlikely to exist (Stewart et al. 2012). Therefore, "
    [Show abstract] [Hide abstract] ABSTRACT: As the pulsatile cardiac blood flow drives the heart valve leaflets to open and close, the flow in the vicinity of the valve resembles a pulsed jet through a non-axisymmetric orifice with dynamically changing area. As a result, three-dimensional vortex rings of intricate topology emerge that interact with the complex cardiac anatomy and give rise to shear layers, regions of recirculation, and flow instabilities that could ultimately lead to transition to turbulence. Such complex flow patterns, which are inherently valve- and patient-specific, lead to mechanical forces at scales that can cause blood cell damage and thrombosis, increasing the likelihood of stroke, and trigger the pathogenesis of various life-threatening valvular heart diseases. We summarize present day understanding of flow phenomena induced by heart valves, discuss their linkage with disease pathways, and emphasize the research advances required to translate in depth understanding of valvular hemodynamics into effective patient therapies.
    Full-text · Article · Jan 2016
    • "There is ample of evidence pointing to a relationship between LV pathology and intraventricular flow patterns, notably the dynamics of the MVR (Hong et al. 2008, Carlhäll & Bolger 2010, Charonko et al. 2013, Mangual et al. 2013). The interaction of the MV leaflets and supporting structures with the blood flow, however, is so complex (Charonko et al. 2013) that a simple correlation among those factors is unlikely to exist (Stewart et al. 2012). Therefore, "
    [Show abstract] [Hide abstract] ABSTRACT: As the pulsatile cardiac blood flow drives the heart valve leaflets to open and close, the flow in the vicinity of the valve resembles a pulsed jet through a non-axisymmetric orifice with dynamically changing area. As a result, three-dimensional vortex rings of intricate topology emerge that interact with the complex cardiac anatomy and give rise to shear layers, regions of recirculation, and flow instabilities that could ultimately lead to transition to turbulence. Such complex flow patterns, which are inherently valve- and patient-specific, lead to mechanical forces at scales that can cause blood cell damage and thrombosis, increasing the likelihood of stroke, and trigger the pathogenesis of various life-threatening valvular heart diseases. We summarize present day understanding of flow phenomena induced by heart valves, discuss their linkage with disease pathways, and emphasize the research advances required to translate in depth understanding of valvular hemodynamics into effective patient therapies.
    Article · Dec 2015
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