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In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography
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Index of myocardial performance is afterload dependent in the normal and abnormal left ventricle

Steven J Lavine1

  • 1Wayne State University and University of Florida / Jacksonville, FACC, Cardiovascular Center, Jacksonville, FL 32209, USA. steven.lvine@jax.ufl.edu

Journal of the American Society of Echocardiography : Official Publication of the American Society of Echocardiography
|April 23, 2005
PubMed

Insights

The index of myocardial performance (IMP) is afterload dependent in normal and dysfunctional left ventricles (LV). Altering arterial pressure significantly impacts IMP, affecting isovolumic indices and ejection time differently across conditions.

Area of Science:

  • Cardiology
  • Physiology
  • Echocardiography

Background:

  • The index of myocardial performance (IMP) is a prognostic systolic-diastolic index.
  • Its utility in dilated cardiomyopathy and postmyocardial infarction is established.
  • The effect of afterload on IMP in normal and dysfunctional left ventricles (LV) requires systematic evaluation.

Purpose of the Study:

  • To systematically evaluate the impact of afterload alteration on the index of myocardial performance (IMP).
  • To assess IMP changes in normal, acutely dysfunctional, and chronically dysfunctional left ventricles (LV).

Main Methods:

  • Studied 15 mongrel dogs under baseline, acute LV dysfunction, and chronic LV dysfunction conditions.
  • Atrial pacing was employed, with arterial pressure manipulated using nitroprusside (NTP) and methoxamine (Methox).
  • Hemodynamic and pulsed Doppler data (transmitral and transaortic) were acquired.

Main Results:

  • In normal LV, IMP was unaffected by NTP but reduced by Methox due to shortened isovolumic contraction time (ICT).
  • Acute LV dysfunction showed IMP decline with NTP (shortened ICT and isovolumic relaxation time) and increase with Methox.
  • Chronic LV dysfunction revealed IMP reduction with NTP (reduced ICT, isovolumic relaxation time; prolonged LV ejection time) and significant increase with Methox (increased ICT, isovolumic relaxation time; reduced LV ejection time).
  • LV systolic pressure and LV ejection fraction independently predicted IMP.

Conclusions:

  • The index of myocardial performance (IMP) demonstrates afterload dependency in normal left ventricles (LV).
  • IMP is afterload dependent in both acute and chronic LV dysfunction, influencing isovolumic indices and LV ejection time reciprocally.
  • Further systematic investigation is necessary for IMP to be a reliable prognostic indicator.
Abstract

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