Tau,left ventricular diastolic time constant,is the most established index to describe left ventricular diastolic function.Tau has been commonly derived only as an invasive measurement in the catheter lab,where it is inconvenient,expensive and time consuming.In 1992,a non-invasive formula was proposed in Harvard to calculate Tau in an Echo lab.[1]Five years later,it was clinically corroborated by Scalia,et al.[2]Unfortunately,we think this method is incorrect.On top of the bold assumptions used in the mathematical deduction process,[3]there are logical flaws in the Harvard formula.
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