Quantification of aortic regurgitation by Doppler echocardiography: a new method evaluated in pigs

Computational analysis of the effect of mitral and aortic regurgitation on the function of ventricular assist devices using 3D cardiac electromechanical model

Valvular insufficiency affects cardiac responses and the pumping efficacy of left ventricular assist devices (LVADs) when patients undergo LVAD therapy. Knowledge of the effect of valvular regurgitation on the function of LVADs is important when treating heart failure patients. The goal of this study was to examine the effect of valvular regurgitation on the ventricular mechanics of a heart under LVAD treatment and the pumping efficacy of an LVAD using a computational model of the cardiovascular system. For this purpose, a 3D electromechanical model of failing ventricles in a human heart was coupled with a lumped-parameter model of valvular regurgitation and an LVAD-implanted vascular system. We used the computational model to predict cardiac responses with respect to the severity of valvular regurgitation in the presence of LVAD treatment. An LVAD could reduce left ventricle (LV) pressure (up to 34%) and end-diastolic ventricular volume (up to 80%) and maintain cardiac output at the estimated flow rate from the LVAD under the condition of mitral regurgitation (MR); however, the opposite would occur under the condition of aortic regurgitation (AR). Considering these physiological responses, we conclude that AR, and not MR, diminishes the pumping function of LVADs.

Experimental investigation of pulsatile flows in tubes

Based on cam-piston-valve arrangement, a mechanical pulsatile flow generator is designed to investigate sinusoidal flow and other types of pulsatile flow in straight rigid tube. Measurement reveals the relation between pressure gradient and flow rate. Numerical simulation using the k-epsilon turbulence model are carried out to compare the pulsatile flow produced by the generator with a sinusoidal flow and a physiological flow in a rigid tube. The results show that the pulsatile flow generated has similar dynamic properties to the physiological flow. Hence, the present setup can be used for in-vitro investigation of biofluid phenomena.