Physiologic Determinants of Mitral Inflow Pattern Using a Computer Simulation: Insights into Doppler Echocardiography in Diverse Phenotypes

BACKGROUND: Although echo Doppler recordings of mitral inflow patterns are often employed clinically to identify "diastolic dysfunction," abnormal flow profiles may be seen in a diverse set of disorders in which the specific physiologic determinants are not well defined. METHODS: We used a validated cardiovascular simulation model to assess the effects of four hemodynamic parameters on Doppler measures of LV filling: (1) total blood volume, (2) diastolic stiffness (LV Beta), (3) systemic vascular resistance (SVR), and (4) pulmonary vascular resistance (PVR). In each simulation, we calculated instantaneous flow through the mitral valve as a function of time. RESULTS: Increases in blood volume led to an increase in the E:A ratio and a decrease in deceleration time (DT), such that for every 100 mL of volume, DT decreased by approximately 3 ms. Increases in LV Beta increased the E:A ratio and decreased DT such that for every 0.005 mmHg/mL increase in LV Beta, DT decreased by approximately 8 ms. While changes in SVR did not significantly alter the Doppler pattern, increases in PVR effected a prolongation of DT and an impaired relaxation E:A pattern. Increasing blood volume and LV Beta simultaneously was additive, while increasing PVR attenuated the effect of increasing volume on the E:A ratio. CONCLUSIONS: Computer simulations demonstrate that both blood volume and LV stiffness significantly impact the mitral inflow profile indicating that both filling pressure and intrinsic properties of the ventricle are contributors. These data confirm that there are multiple determinants of the Doppler mitral inflow pattern and suggest a new approach toward understanding complex physiologic interactions.