PMID: 8988442Aug 1, 1996Paper

Similarities and differences in the time course of mechanical activity of the canine myocardium and isovolumic left ventricle

The Japanese Journal of Physiology
O N Nwasokwa

Abstract

The isovolumic non-ejecting left ventricle (LV) is functionally analogous to the isometric myocardium and the curve of the time course of left ventricular isovolumic pressure, P(t), resembles the curve of the time course of myocardial isometric force, F(t). In this study therefore, we first tested the hypothesis that the same general empirical model that fit F(t) and L(t), the isotonic shortening curve, will also fit P(t) by evaluating the model P(t) = P0 + C(t/A)B exp[1-(t/A)]B in 8 Suga-Sagawa isolated cross-circulated canine left ventricles. P0 is the end-diastolic pressure; A, B, and C are parameters. We went further to compare the time course of P(t) to those of F(t) and L(t) exploiting their common basic analytical models not only to characterize similarities but also to highlight differences between them. To obtain curves of P(t), we inserted a latex balloon in the LV and injected water into it and recorded the isovolumic pressure curve, P(t), in each of 8 ventricles. Eight in situ right ventricular papillary muscles of the isolated canine heart were also studied with a servo system that clamped length or force to produce F(t) or L(t). Each curve, P(t), F(t), or L(t) was fit with the above model by Marquardt's algorithm ...Continue Reading

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