Maximal rate of pressure rise and time parameters in the right ventricle under isovolumic conditions. Investigations in the canine heart-lung preparation.

In contrast to the left ventricle, the maximal rate of intraventricular pressure rise in the right ventricle does not occur within the isovolumic phase of the contraction. Occlusion of the pulmonary artery by inflation of a balloon during the diastole causes an isovolumic systole of the following heart beat. The canine heart-lung preparation was used to test whether dP/dtmax measured isovolumically and the peak ventricular pressure Pmax as well as the parameters derived are useful indices for the contractile state of the right ventricle. Changes only of the aortic pressure influence neither dP/dtmax, Pmax and the time values from the onset of contraction to dP/dtmax (t-dP/dtmax), nor the time to Pmax (t-Pmax). A rise in heart frequency leads to an increase in dP/dtmax and Pmax at lowered enddiastolic pressure. It does not influence the time interval t-dP/dtmax and t-Pmax. With augmented diastolic filling, dP/dtmax as well as Pmax increase, and t-dP/dtmax and t-Pmax are extended. The present study suggests that dP/dtmax and Pmax measured isovolumically provide accurate and practical measurements of right ventricular contractility, provided that changes in enddiastolic pressure and heart frequency are taken into account. The time parameters are found to be not useful.