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

Department of Mechanical Engineering, Virginia Tech, 100 Randolph Hall, Blacksburg, VA, 24060, USA.
Annals of Biomedical Engineering (Impact Factor: 3.23). 02/2013; 41(5). DOI: 10.1007/s10439-013-0755-0
Source: PubMed


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.

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    • "from the lateral wall along the apical region toward the septum [8] [10] [15] [22] [28] [40] [42] [48] [49]. It is noted that the present simulations not only predict the ventricular flow that is consistent with the previous works but also predict the flow inside the LA that is generally in line with clinical measurements. "
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    ABSTRACT: In the present study, we investigate the hemodynamics inside left atrium and understand its impact on the development of ventricular flow patterns. We construct the heart model using dynamic computed tomographic images and perform simulations using immersed boundary method based flow solver. The results show that the atrial hemodynamics is characterized by a circulatory flow generated by the left pulmonary veins and a direct stream from the right ones. The complex interaction of the vortex rings formed from each of the pulmonary veins leads to vortex breakup and annihilation, thereby producing a regularized flow at the mitral annulus. A comparison of the ventricular flow velocities between the physiological and a simplified pipe-based atrium model shows that the overall differences are limited to about 10% of the peak mitral flow velocity. The implications of this finding on the functional morphology of the left heart as well the computational and experimental modeling of ventricular hemodynamics are discussed.
    Full-text · Article · Sep 2015 · Journal of Biomechanical Engineering
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    • "The onset mitral flow patterns were obtained by Eriksson et al. [28] using path lines traced for 25 msec. Charonko et al. [29] employed 2D phase-contrast MRI to calculate the temporal variation of pressure drop with the mitral flow velocity and discuss normal LV filling with vortices. The kinetic energy of inflow was calculated for 12 subjects. "
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    ABSTRACT: Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the mitral valve are obtained for flow acceleration and deceleration. Bernoulli energy flux delivered to blood from ventricular dilation is practically balanced by the energy influx and the rate change of kinetic energy in the ventricle. The rates of work done by shear and energy dissipation are small. The dynamic and energy characteristics of the 2D results are comparable to those of a 3D model.
    Full-text · Article · Aug 2015 · Computational and Mathematical Methods in Medicine
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    • "This behavior has been well established in the past [1] [45] [46] [48] [58] [59] although, the structure of the vortex characterized here is more complex with small tube-like vortices coiling around a central core. The vortex ring subsequently disintegrates and a clockwise circulatory flow pattern is produced in the ventricular cavity that sweeps the flow from the lateral wall along the apical region towards the septum [22] [31] [45] [46] [48] [49] [60] [61]. Although this pattern of flow redirection was previously conjectured to be hydrodynamically efficient [46] [47], later studies have indicated that the effect of the flow patterns on pumping efficiency is quite small and that it is mixing and washout that are more dependent on the intraventricular flow pattern, [22] [57]. "
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    ABSTRACT: The impact of surface trabeculae and papillary muscles on the hemodynamics of the left ventricle (LV) is investigated using numerical simulations. Simulations of ventricular flow are conducted for two different models of the LV derived from high-resolution cardiac computed tomography (CT) scans using an immersed boundary method-based flow solver. One model comprises a trabeculated left ventricle (TLV) that includes both trabeculae and papillary muscles, while the second model has a smooth left ventricle that is devoid of any of these surface features. Results indicate that the trabeculae and papillary muscles significantly disrupt the vortices that develop during early filling in the TLV model. Large recirculation zones are found to form in the wake of the papillary muscles; these zones enhance the blockage provided by the papillary muscles and create a path for the mitral jet to penetrate deeper into the ventricular apex during diastole. During systole, the trabeculae enhance the apical washout by ‘squeezing’ the flow from the apical region. Finally, the trabeculae enhance viscous dissipation rate of the ventricular flow, but this effect is not significant in the overall power budget.
    Full-text · Article · May 2015 · Theoretical and Computational Fluid Dynamics
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