Impact of ejection on magnitude and time course of ventricular pressure- generating capacity

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

Research output: Contribution to journalArticlepeer-review

53 Scopus citations

Abstract

This study focuses on elucidating how ventricular afterloading conditions affect the time course of change of left ventricular pressure (LVP) throughout the cardiac cycle, with particular emphasis on revealing specific limitations in the time-varying elastance model of ventricular dynamics. Studies were performed in eight isolated canine hearts ejecting into a simulated windkessel afterload. LVP waves measured (LVP(m)) during ejection were compared with those predicted (LVP(pred)) according to the elastance theory. LVP(m) exceeded LVP(pred) from a time point shortly after the onset of ejection to the end of the beat. The instantaneous difference between LVP(m) and LVP(pred) increased steadily as ejection proceeded and reached between 45 and 65 mmHg near end ejection. This was in large part due to an average 35-ms prolongation of the time to end systole (t(es)) in ejecting compared with isovolumic beats. The time constant of relaxation was decreased on ejecting beats so that, despite the marked prolongation of t(es), the overall duration of ejecting contractions was not greater than that of isovolumic beats. The results demonstrate a marked ejection-mediated enhancement and prolongation of ventricular pressure-generating capacity during the ejection phase of the cardiac cycle with concomitant acceleration of relaxation. None of these factors are accounted for by the time-varying elastance theory.

Original languageEnglish (US)
Pages (from-to)H899-H909
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number3 34-3
DOIs
StatePublished - 1993

All Science Journal Classification (ASJC) codes

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

Keywords

  • afterload
  • contractility
  • elastance
  • end-systolic pressure-volume relation
  • internal ventricular resistance

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