Role of Computational Simulations in Heart Valve Dynamics and Design of Valvular Prostheses

Abstract

Computational simulations are playing an increasingly important role in enhancing our understanding of the normal human physiological function, etiology of diseased states, surgical and interventional planning, and in the design and evaluation of artificial implants. Researchers are taking advantage of computational simulations to speed up the initial design of implantable devices before a prototype is developed and hence able to reduce animal experimentation for the functional evaluation of the devices under development. A review of the reported studies to date relevant to the simulation of the native and prosthetic heart valve dynamics is the subject of the present paper. Potential future directions toward multi-scale simulation studies for our further understanding of the physiology and pathophysiology of heart valve dynamics and valvular implants are also discussed.

FIGURE 1

An example of reconstructed human mitral valve from 3D echocardiographic data (Courtesy of Dr. Hyunggun Kim, Ph.D., University of Texas Medical Center at Houston, Texas).

FIGURE 2

Sequence of displacements of the leaflets of a pericardial bioprosthetic valve during a cardiac cycle (Reprinted from Kim et al. with permission from Springer Science + Business Media).

FIGURE 3

Comparison of the valve orifice in the fully open position (a: Normal tri-leaflet valve geometry; b: simulated bicuspid valve geometry where the two leaflets on the right are fused) and the von Mises stress distribution on the leaflets in the fully closed position (c: tri-leaflet aortic valve; and d: simulated bicuspid aortic valve) from dynamic FE analysis from Jermihov et al..

FIGURE 4

Results from a 2D FSI analysis of an aortic valve: (a) pressure contours and stream line plots with the leaflet in the fully open position; (b) and (c): Vorticity plots on the leaflet surfaces. Physiologically realistic material property was employed for the leaflets and the fluid dynamic analysis included physiologically realistic Reynolds numbers (Courtesy of Sarah Vigmostad, Ph.D. of the University of Iowa).

FIGURE 5

Comparison of experimentally measured (left column) viscous shear stresses (a and c) and Reynolds shear stresses (e) with computational results (b and d) of viscous shear stresses (Reprinted from Ge et al. with permission from Springer Science + Business Media).

FIGURE 6

Disperson of particles simulating platelets during forward flow phase (top row) and during the regurgitant flow phase with the leaflets in the fully closed position (bottom row) are compared for open pivot (left column) and recessed hinge (right column) bi-leaflet valve models (Reprinted from Dumont et al. with permission from ASME Press).

FIGURE 7

Plots of vorticity contours (left column), viscous shear stress (middle column), and platelet activation parameter (right column) on the atrial side of the leaflet during the first rebound after closing of the leaflet with two bi-leaflet heart valve models. The leaflet traverse angle from the fully open position to the fully closed position was 55° (for valve model plots in the top row) and 64° (for valve model plots in the bottom row) (Reprinted from the J. Heart Valve Dis. with permission from ICR Publishers).

FIGURE 8

Micro-scale 2D analysis of red blood cell–platelet interaction with red blood cells (RBCs) assumed as semirigid 8 μm elliptical particles and platelets as rigid 2 μm discoids (highlighted in circles) at a Reynolds number of 1 and hematocrit of 15%: (a) Plot of velocity contours and RBC/platelet distribution at various time intervals. It can be observed that RBCs move toward the core region and the platelets are marginated to the channel surfaces at t = 8. (b) The analysis with RBCs assumed to be 8 μm discoids (left column) shows similar margination of platelets to the channel surface where as when reduced in size to 4 μm (right column), platelet margination is not observed indicating that the relative size between the RBCs and platelets are more important than the shape of the cells (Reprinted from AlMomani et al. with permission from Springer Science + Business Media).