Contractile strength and mechanical efficiency of left ventricle are enhanced by physiological afterload

D. Burkhoff, P. P. De Tombe, W. C. Hunter, D. A. Kass

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Recent studies have shown that at the same end-systolic volume, ejecting beats can achieve a higher end-systolic pressure than isovolumic beats. The purpose of this study was to assess the metabolic cost, in terms of oxygen consumption (MV̇O2), and efficiency, in terms of the relation between MV̇O2 and pressure-volume area (PVA), of this increase in strength during ejection. The slope of the end-systolic pressure-volume relation (ESPVR) (E(es)) was greater during ejecting than isovolumic contractions when ejection fraction (EF) was greater than ~30%, indicating an increase in contractile strength. The difference in E(es) between the two modes of contraction was as much as 30% at EFs of 60%. In contrast, the slope of the MV̇O2-PVA relation was less during ejecting than isovolumic contractions, indicating a decrease in MV̇O2 at any given PVA. The difference in slope was as much as 20% at EFs of 60%. Thus afterload conditions, allowing substantial fiber shortening, shift the ESPVR toward greater contractile strength and increase the metabolic efficiency when viewed in terms of the relation between MV̇O2 and total mechanical energy generation (PVA) by the ventricle. This may reflect an energetically favorable effect of shortening on muscle force-generating capability.

Original languageEnglish (US)
Pages (from-to)H569-H578
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number2 29-2
StatePublished - 1991
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


  • End-systolic pressure-volume relationship
  • Isolated canine heart
  • Myocardial efficiency
  • Oxygen consumption
  • Pressure-volume area
  • Windkessel model


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