A practical technique was developed for in vivo determinations of the mechanical properties of canine left ventricle. A “quick stretch” was accomplished by rapid injection of isotonic saline into the ventricle during isovolumetric systole. The experimental pressure-volume data and a stress-strain analysis of the left ventricle as a thick-walled sphere permitted determination of the effective elastic modulus as a function of the mean circumferential stress. The elastic modulus E was found to be a linear function of the mean tangential stress σ throughout the isovolumetric systolic period; the slope (K, modulus of stiffness) of the Eversus σ curve was 18.8 with a standard deviation of 0.9.

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