Calculation of Left Ventricular Relaxation Time Constant-Tau in Humans by Continuous-Wave Doppler

Xufang Bai*
Henderson Research Center, McMaster University, Hamilton, Ontario, Canada

2008 Bentham Science Publishers Ltd.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

* Address correspondence to this author at the Henderson Research Center, McMaster University, Hamilton, Ontario, Canada; E-mail:


Left ventricular relaxation time constant, Tau, is the best index to evaluate left ventricular diastolic function, but the measurement is only available traditionally in catheter lab. In Echo lab, several methods of non-invasive measurement of Tau have been tried since 1992, however almost all the methods are still utilizing the same formula to calculate Tau as in catheter lab, which makes them inconvenient, time-consuming and sometimes not very accurate. Based on Weiss’ formula and simplified Bernoulli’s equation, a simple method is developed by pure mathematical derivative to calculate Tau by continuous-wave Doppler in patients with mitral regurgitation.