A new Doppler method for assessing left ventricular diastolic stiffness based on principles of flow wave propagation: mathematical basis and review of the method

Abstract

Color flow imaging shows that the transmitral flow is initially directed to the left ventricular (LV) apex and then turns around facing the aortic valve. A pulsed wave Doppler sample placed in the LV outflow tract (LVOT) records two peaks of diastolic flow waves, Er and Ar waves, which follow E and A waves of the transmitral flow respectively. The Er and Ar waves represent transmitted E and A flow waves to the LVOT. Our preliminary clinical and hemodynamic data in human subjects have shown that the A-Ar interval, which is the time taken for the A velocity wave to propagate from the mitral valve to the LVOT, is shorter in those with LV hypertrophy (LVH), the aged and those with elevated LV late diastolic stiffness, suggesting faster A wave transmission in those with stiffer ventricles. We also have shown that velocity and pressure waves propagate similarly in the arterial system. This led to the hypothesis that the A wave transmission inside the LV may follow the principles described in the Moens-Korteweg equation, or a modification of it, and the velocity of A wave transmission inside the LV may reflect its late diastolic stiffness. Studies designed to test this hypothesis in a pulsatile LV model showed a linear relationship between the rate of diastolic flow wave propagation inside the LV and its stiffness. These preliminary data suggest that the velocity of A wave transmission inside the LV reflects LV late diastolic stiffness non-invasively. It is expected to be independent of a direct effect of heart rate and of preload.