A simulation of three-dimensional systolic flow dynamics in a spherical ventricle: effects of abnormal wall motion

Alterations in left ventricle (LV) wall motion induced by ischemia will affect flow dynamics, and these altered flow fields can be used to evaluate LV pumping efficiency. LV chamber flow fields were obtained in this study by solving the discretized three-dimensional Navier-Stokes equations for viscous, incompressible unsteady flow by using the finite analytic method. Several cases of abnormal wall motion (AWM) were simulated by a manipulation of the boundary conditions to produce regions of hypokinesis, akinesis, and dyskinesis. These solutions were used to determine the central ejection region (CER), defined as the region of flow domain in which the obtained velocity field vectors are aligned +/- 3 degrees from the LV long axis. A CER coefficient was computed from information on the location and orientation of the CER within the LV cavity. Contraction of the spherical ventricle produced a vector field that was symmetric with respect to the long axis. For the simulations of AWM, an asymmetrical flow pattern developed, became more pronounced with increasing severity of AWM, and resulted in a shorter CER that shifted toward the ischemic region. The CER coefficients decreased monotonically with increased severity in AWM from 0.948 in the normal case to a low of 0.164 for the most severe case of AWM. The CER coefficient quantitatively displayed the sensitivity of the flow patterns to even moderate degrees of hypokinesis. In addition, visualization of the three-dimensional flow field reinforced the necessity of three-dimensional simulations to capture aspects of the flow that existing methods of two-dimensional flow imaging that use ultrasound may miss.