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

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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent advances in imaging techniques have allowed physicians to obtain robust measurements of intracardiac flows in the clinical setting. Consequently, the physiological implications of intraventricular fluid dynamics are beginning to be understood. Initial data show that these flows involve complex fluid-structure interactions and mixing phenomena that are modified by disease. Here we critically review the most important aspects of intraventricular fluid mechanics relevant for clinical applications. We discuss current image and numerical methods for assessing intraventricular flows, as well as implemented approaches to analyze their impact on cardiac function. The physiological and clinical insights provided by such techniques are discussed both in health and in disease. The final goal is to encourage research in the application of fluid dynamic foundations to patient-based clinical data. A huge potential is anticipated not only in terms of the basic science of large-scale biological systems, but also in practical terms of improving patient care.
    Annual Review of Fluid Mechanics 01/2015; 47(1):315. DOI:10.1146/annurev-fluid-010814-014728 · 11.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The diastolic intraventricular ring vortex formation and pinch-off process may provide clinically useful insights into diastolic function in health and disease. The vortex ring formation time (FT) concept, based on hydrodynamic experiments dealing with unconfined (large tank) flow, has attracted considerable attention and popularity. Dynamic conditions evolving within the very confined space of a filling, expansible ventricular chamber with relaxing and rebounding, and viscoelastic muscular boundaries diverge from unconfined (large tank) flow and encompass rebounding walls' suction and myocardial relaxation. Indeed, clinical/physiological findings seeking validation in vivo failed to support the notion that FT is an index of normal/abnormal diastolic ventricular function. Therefore, FT as originally proposed cannot and should not be utilized as such an index. Evidently, physiologically accurate models accounting for coupled hydrodynamic and (patho)physiological myocardial wall interactions with the intraventricular flow are still needed to enhance our understanding and yield diastolic function indices useful and reliable in the clinical setting.
    Journal of Cardiovascular Translational Research 01/2015; DOI:10.1007/s12265-015-9607-7 · 2.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. This two-article series proposes that variable forces associated with diastolic RV/LV rotatory intraventricular flows can exert physiologically and clinically important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations and/or maladaptations. Taken in toto, the two-part survey formulates a new paradigm in which intraventricular diastolic filling vortex-associated forces play a fundamental epigenetic role, and examines how heart cells react to these forces. The objectives are to provide a perspective on vortical epigenetic effects, to introduce emerging ideas, and to suggest directions of multidisciplinary translational research. The main goal is to make pertinent biophysics and cytomechanical dynamic systems concepts accessible to interested translational and clinical cardiologists. I recognize that the diversity of the epigenetic problems can give rise to a diversity of approaches and multifaceted specialized research undertakings. Specificity may dominate the picture. However, I take a contrasting approach. Are there concepts that are central enough that they should be developed in some detail? Broadness competes with specificity. Would, however, this viewpoint allow for a more encompassing view that may otherwise be lost by generation of fragmented results? Part 1 serves as a general introduction, focusing on background concepts, on intracardiac vortex imaging methods, and on diastolic filling vortex-associated forces acting epigenetically on RV/LV endocardium and myocardium. Part 2 will describe pertinent available pluridisciplinary knowledge/research relating to mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations and to their epigenetic actions on myocardial and ventricular function and adaptations.
    Journal of Cardiovascular Translational Research 01/2015; DOI:10.1007/s12265-015-9611-y · 2.69 Impact Factor