A comparison of left ventricular volume-pressure relations of excised perfused canine hearts in isovolumic contraction, arrest and fibrillation.

The purpose of the present investigation was to study the effects of various conditions such as beating, arrest and fibrillation on left ventricular (LV) diastolic compliance. In coronary-arterially perfused canine isolated hearts, LV volume-pressure (v-p) relations for both inflation and deflation were obtained by infusing and withdrawing a saline. The v-p curves of inflation and deflation were both sigmoidal, but the resultant v-p relations for deflation produced a shift to the left inflation curves, showing hysteresis between inflation and deflation in three ventricular states. The effect of arrest or fibrillation, especially of fibrillation, on LV distensibility was discernible, and the resultant v-p relations produced a marked shift to the right, showing an apparent decrease in LV volume (LVv) at a given filling pressure. It was concluded that it is very questionable to identify the stiffness of the beating heart with the non-beating heart.