Tau is the best index to describe diastolic function, however, this indispensible index can only be measured in a catheter lab. In our daily clinic, it is dead. Who killed it?
1992, Dr Thomas invented a non-invasive measurement method of Tau and “verified” it experimentally at the same time:
Thomas JD, Flachskampf FA, Chen C, Guererro JL, Picard MH, Levine RA, Weyman AE. Isovolumic relaxation time varies predictably with its time constant and aortic and left atrial pressure: implications for the noninvasive of ventricular relaxation. Am Heart J. 1992;124:1305–1313.
1997, this method was “validated” in Cleveland Clinically:
Scalia GM, Greenberg NL, McCarthy PM, Thomas JD, Vandervoort PM. Noninvasive assessment of the ventricular relaxation time constant in humans by Doppler echocardiography. Circulation. 1997;95:151–155.
Unfortunately, this method is wrong. The formula was developed with too many bold assumptions that inflicted logic flaws:
Horning A, Bai, X. The Harvard method of Tau calculation is incorrect. J Geriatr Cardiol. 2019 May; 16(5): 429–430.
It is common sense that a logically flawed formula cannot be verified with a decent approach. Anyway, quite a few researchers hopped on the bandwagon, kind of like the Emperor’s New Clothes parade. The parade was on and on till recently when almost all the participants left.
Never underestimate the influence of big names. Other Tau researchers found it hard to get their papers published since. Good news is Mindray launched the Tau-measurable Echo machines in 2017 and the machines are sold all over the world except North America. So, in North America, Tau is dead, at least for now.