[Noninvasive estimation of left ventricular relaxation time constant by continuous wave Doppler echocardiography].

In order to develop a new method for estimating left ventricular relaxation time constant (T)noninvasively, continuous wave Doppler echocardiography (CWD) and left heart catheterization (Cath) were performed simultaneously in 25 patients with mitral regurgitation (MR). The MR velocities were recorded by CWD and digitized every 20 ms along the descending limb of the Doppler spectra to obtain the peak rate of decline of pressure gradient (-dPG/dt max) and the instantaneous left ventricular pressure (PO) at the time point of -dPG/dt max. T was then calculated as: T = PO/-dPG/dt max, and compared with T measured from pressure curves by Weiss's method. The result showed that there was a high correlation of T determined by the two techniques (r = 0.94, SEE = 4.36 ms) and there was no significant difference between the two methods. Thus, CWD offers a new and reliable approach to the noninvasive estimation of T in patients with MR.