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Intraventricular filling in the cardiac left ventricle under increasing aortic pressure

Intraventricular filling in the cardiac left ventricle under increasing aortic pressure

Nicholas Nelsen

Mechanical & Aerospace Engineering

Clinical studies using medical imaging have provided evidence of the formation of an intraventricular vortex in the left ventricle (LV) during the diastolic phase of the cardiac cycle. However, the effects of altered aortic pressure on the filling vortex characteristics remain unclear. This is of relevance to hypertensive heart disease and LV hypertrophy, both of which affect over a million patients each year. The goal of this study was to investigate the change in intraventricular filling vortex characteristics inside a physical model of the LV with increasing aortic pressure. A flexible-walled LV physical model with known stiffness was tested in a pulsatile flow loop driven by a programmable piston pump. The flow loop was filled with a blood analogue fluid consisting of 36% by volume of water-glycerin. Absolute pressures were measured at the ventricular and aortic positions using pressure transducers. Volumetric flow rates into and out of the LV model were measured using ultrasonic flow probes. The flow circuit was initially tuned to physiological values of aortic pressure, cardiac output, ejection fraction, and E/A ratio. We then iteratively adjusted the aortic pressure by increasing outflow resistance without changing other variables. 2D time-resolved particle image velocimetry measurements were conducted to visualize the intraventricular flow during diastole and calculate the filling vortex circulation. Comparisons of the filling vortex circulation with varying aortic pressure relative to baseline hemodynamics will be presented.