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. 1977 May;267(1):63–74. doi: 10.1113/jphysiol.1977.sp011801

Reduction of the duration of isovolumic relaxation in the ejecting left ventricle of the dog: residual volume clamping

Hiroyuki Suga 1,2,*, Ken-Ichi Yamakoshi 1,2
PMCID: PMC1283602  PMID: 874863

Abstract

1. The individual effects of stroke volume and speed of ejection on the duration of the isovolumic relaxation phase were analysed in the canine left ventricle with a constant end-systolic residual volume.

2. A new technique was employed to maintain the ventricular end-systolic residual volume at a desired constant value regardless of wide changes in stroke volume and speed of ejection in a given inotropic background.

3. The duration of isovolumic relaxation, which was defined to be the time taken for ventricular pressure to fall from its end-systolic level to its 75, 50 and 25% levels, markedly decreased with increases in stroke volume. The reduction amounted to as much as 30-50% when stroke volume was increased from zero (isovolumic) to 20-25 ml.

4. The degree of shortening of the duration of isovolumic relaxation was largely independent of changes in speed of ejection which ranged from about 100-800 ml./sec at a constant stroke volume of 15 ml.

5. It was therefore concluded that stroke volume itself could be a major determinant of the duration of isovolumic relaxation.

6. It was speculated that the mechanism of the observed phenomenon might be a manifestation of the uncoupling effect of muscle shortening on contractile state.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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