Hydrodynamics of Cardiac Diastole

Abstract

Left ventricular diastole (filling) is a complex process with many features and coupled compensatory mechanisms which coordinate to maintain optimal filling and ejection of the left ventricle. Diastolic filling is controlled by the left ventricular recoil, relaxation, and compliance as well as atrial and ventricular pressures making left ventricular diastolic dysfunction very difficult to understand and diagnose. An improved understanding of these unique flows is important to both the fundamental mechanics of the cardiac diastolic filling as well as the development of novel and accurate diagnostic techniques.

This work includes studies of in-vivo and in-vitro vortex rings. Vortex rings created in the left ventricle past the mitral valve during diastole are produced in a confined domain and are influenced by the left ventricular walls. Therefore, an in-vitro analysis of the formation and decay of vortex rings within confined cylindrical domains using particle image velocimetry was conducted. Varying mechanisms of vortex ring breakdown were observed over a wide range of Reynolds numbers, and an analytical model for vortex ring circulation decay of laminar vortex rings was developed. Also, in this work a novel method for analyzing color M-mode echocardiography data using a newly developed automated algorithm is introduced which examines the pressure gradients and velocities within the left ventricle. From this analysis, a new diagnostic filling parameter is introduced which displays a greater probability of detection of diastolic dysfunction over the conventionally used diagnostic parameter.