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Is tau a preload-independent measure of isovolumetric relaxation?

S K Varma1, R M Owen, M L Smucker

  • 1Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville.

Circulation
|December 1, 1989
PubMed

Insights

Prolongation of myocardial tau is observed in heart disease, but its cause is unclear. This study found that decreasing preload in healthy individuals did not alter tau, suggesting it reflects abnormal physiology, not just heart load.

Area of Science:

  • Cardiology
  • Physiology

Background:

  • Prolongation of myocardial tau is a known finding in various myocardial diseases.
  • The cause of prolonged tau remains uncertain, with debate on whether it reflects abnormal myocardial physiology or disease-related excessive load.

Purpose of the Study:

  • To investigate the effect of an isolated decrease in preload on myocardial tau in healthy individuals.
  • To determine if prolonged tau is indicative of abnormal myocardial physiology or a consequence of increased cardiac workload.

Main Methods:

  • Six healthy patients underwent inferior vena cava occlusion to induce an isolated decrease in preload before reflex changes occurred.
  • Cardiac contractions were analyzed using a computer-based digitization routine.
  • Myocardial tau was calculated using logarithmic (TL), derivative (TD), and Mirsky's (T1/2) methods before and after preload reduction.

Main Results:

  • Inferior vena cava occlusion successfully reduced left ventricular end-diastolic pressure without significantly altering left ventricular systolic pressure or heart rate.
  • No significant changes in tau (TL, TD, or T1/2) were observed after the isolated decrease in preload.
  • Extrapolated baseline pressure from isovolumetric relaxation remained unchanged.

Conclusions:

  • Isolated reduction of preload in healthy individuals does not alter myocardial tau.
  • The findings suggest that prolonged tau may represent abnormal myocardial physiology rather than being solely a consequence of increased cardiac load.

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