Extracardiac pressure changes do not alter contractile function of the isolated left ventricle

Mark G. Midei, W. Lowell Maughan, Robert Y. Oikawa, David A. Kass, Kiichi Sagawa

Research output: Contribution to journalArticle

Abstract

To determine whether or not extracardiac pressure has an effect on left ventricular contractile function, we analyzed pressure-volume relationships of six isolated, perfused canine hearts in an air-tight chamber. The chamber pressure was set at -60, -30, 0, 30 and 60 mm Hg and left ventricular pressure-volume relationships studied. The slope (Ees) and volume axis intercept (V0) of the transmural pressure-volume relationship were used to compare the pump functions of an individual heart at the different extracardiac pressures applied. No significant difference in either Ees or V0 was seen with different extracardiac pressures. During isovolumic ventricular contraction, developed left ventricular pressure did not change over the range of extracardiac pressures applied. The same was true during ejecting contraction; when the downstream pressure of the computer simulated afterload circuit and the venous filling pressure of the preload circuit were changed in parallel with the extracardiac pressure, pressur-volume loops remained identical throughout their course for all of the extracardiac pressures applied. We conclude that (1) transmural pressure is the overwhelmingly dominant loading factor governing LV contraction, and (2) myocardial contractile function is unaffected by the absolute value of extracardiac pressure.

Original languageEnglish (US)
Pages (from-to)347-359
Number of pages13
JournalAnnals of biomedical engineering
Volume15
Issue number3-4
StatePublished - May 1987

Keywords

  • End-systolic pressure-volume relationship
  • Isolated canine heart
  • Transmural pressure
  • Wall tension

ASJC Scopus subject areas

  • Biomedical Engineering

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