A laboratory investigation of the flow in the left ventricle of a human heart with prosthetic, tilting-disk valves

Abstract

The understanding of the phenomena involved in ventricular flow is becoming more and more important because of two main reasons: the continuous improvements in the field of diagnostic techniques and the increasing popularity of prosthetic devices. On one hand, more accurate investigation techniques gives the chance to better diagnose diseases before they become dangerous to the health of the patient. On the other hand, the diffusion of prosthetic devices requires very detailed assessment of the modifications that they introduce in the functioning of the heart. The present work is focussed on the experimental investigation of the flow in the left ventricle of the human heart with the presence of a tilting-disk valve in the mitral position, as this kind of valve is known to change deeply the structure of such a flow. A laboratory model has been built up, which consists of a cavity able to change its volume, representing the ventricle, on which two prosthetic valves are mounted. The facility is designed to be able to reproduce any arbitrarily assigned law of variation of the ventricular volume with time. In the present experiment, a physiologically shaped curve has been used. Velocity was measured using a feature-tracking (FT) algorithm; as a consequence, the particle trajectories are known. The flow has been studied by changing both the beat rate and the stroke volume. The flow was studied both kinematically, examining velocity and vorticity fields, and dynamically, evaluating turbulent and viscous shear stresses, and inertial forces exerted on fluid elements. The analysis of the results allows the identification of the main features of the ventricular flow, generated by a mitral, tilting-disk valve, during the whole cardiac cycle and its dependence on the frequency and the stroke volume

Role of Mitral Annulus Diastolic Geometry on Intraventricular Filling Dynamics

“…Comparing the two mitral annuli geometries, similar flow features were observed, which qualitatively resemble other previously published data on intraventricular flow, both in vitro and in vivo [1,6,7,42,43]. Two counter-rotating vortices form during inflow with the vortex closest to the lateral wall quickly dissipating.…”

“…A considerable number of experimental studies using LV physical models [1,4,20,41] have commonly used MV prostheses with circular annulus geometries to study intraventricular filling patterns. This study represents the first one to address the effect of the mitral annulus change in geometry on the left ventricular filling process and efficiency.…”

“…The flow through the native mitral annulus and the two MV leaflets results in the generation of an inflow vortex ring within the LV, which has been investigated experimentally and computationally by several researchers [1][2][3][4][5][6][7][8]. Heart disease manifestations, such as dilated cardiomyopathy and diastolic dysfunction, have been shown to alter the inflow vortex ring characteristics [9,10] and mixing of blood within the LV [11,12].…”

CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

“…e velocity components along the x-and z-axes, respectively, u and w, have been measured using the feature tracking (FT), a technique based on the image analysis [45]. A high-speed camera (CMOS with a resolution of 1280 × 1024 pixels) acquires images at 250 frames per second for 40 s during each experiment, while a green laser light sheet (wavelength of 532 nm) illuminates the acquisition area.…”

Steady and unsteady laminar flows of Newtonian and generalized Newtonian fluids in a planar T‐junction

“…In a large number of investigations on blood flow, the rheology is simplified and it is assumed that blood has a linear stress/strain relationship [5,[8][9][10][11]. This simplification may be acceptable to a first approximation, especially in large blood vessels under steady conditions, but a more realistic fluid description is required for more accurate fluid dynamics.…”