Left ventricular force length relations of isovolumic and ejecting contractions

Karl Weber, J. S. Janicki, L. L. Hefner

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

To determine the interrelationships between ejecting and isovolumic force length relations and the extent to which the left ventricle will shorten, data obtained in 27 isolated, servo regulated hearts were examined. For each heart a series of contractions, variably loaded (ejection pressure, 20 mmHg to isovolumic state; end diastolic pressure, 1-30 mmHg), were analyzed. Perfusate calcium concentration (12-18 mg/100 ml) or an infusion of norepinephrine (0.4-1.4 μg/min) or propranolol (0.12-0.50 mg/min) was used to manipulate contractile state. Mural force, midwall circumferential length (L), and shortening (ΔL) were derived for a thickwalled sphere and normalized by the cross sectional area of muscle and length at zero end diastolic pressure. It was found that within the physiological range examined total and active force were essentially a linear function of initial L with respective increments or reductions in slope produced by positive or negative shifts in contractile state. The force L relations obtained isovolumically and at end ejection were virtually identical. For a given ejection pressure, end systolic L was constant, despite variations in filling and therefore independent of initial L and ΔL; moreover, the L to which the ventricle shortened was determined by the course of the systolic force L relation. Thus, irrespective of loading, ΔL occurs within the confines of the contractile state dependent isovolumic force L relation and where the latter is equivalent to the end systolic force length relation.

Original languageEnglish (US)
Pages (from-to)337-343
Number of pages7
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume231
Issue number2
StatePublished - 1976
Externally publishedYes

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Blood Pressure
Propranolol
Heart Ventricles
Norepinephrine
Calcium
Pressure
Muscles

All Science Journal Classification (ASJC) codes

  • Medicine(all)

Cite this

Left ventricular force length relations of isovolumic and ejecting contractions. / Weber, Karl; Janicki, J. S.; Hefner, L. L.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 231, No. 2, 1976, p. 337-343.

Research output: Contribution to journalArticle

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