Sunday, October 31, 2010

-dp/dt max is equivalent to Tau

Recently, an editorial (1) from Circulation Heart Failure claimed “Tau derived from the monoexponential model is less dependent on loading conditions than peak -dp/dt and has been used as a reliable index for LV relaxation in many clinical and experimental studies.”

I think –dp/dt max and Tau are the SAME in terms of clinical significance.

This is the proof:
Weiss’ formula:
                   P = e(exp)(t /T+B) +C
The derivative of both sides:
                  dp = e(exp)(t /T+B) (1/T )dt    or:
              dp/dt = e(exp)(t /T+B) (1/T )
Since t starts from peak -dp/dt,  when t=0, we have:
      dp/dt max = e(exp)B (1/T ) = e(exp)B /Tau

Because e(exp)B is a constant, it means -dp/dt max and Tau share a relationship of one to one correspondence. We can draw the conclusion that -dp/dt max and Tau are equivalent indices in clinical significance.


(1)   Kazuhiro Yamamoto. The Time Constant of Left Ventricular Relaxation: Extrication from Load Dependence and overestimation of Functional Abnormality. Circ Heart Fail. 2010;3:178-180.

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