[Study of the relaxation phase of the right ventricle]

The purpose of our study was to investigate the existence or not of an isovolumic relaxation period in the right ventricle in experimental animals with normal pressures in the pulmonary artery. Right and left ventricular pressures, pulmonary and aortic pressures (microtransducers), pulmonary flow, ventricular diameters (sonomicrometer), were recorded at the same time, in 10 sheep anesthetized intravenously with pentobarbital. We obtained "off line" the first ventricular pressures derivative, the ventricular volumes and the pressure-volume loops of both ventricles. The minimum systolic right ventricular volume coincided with 0 pulmonary flow, and both with a diastolic pressure value of 0-5 mmHg in that ventricle. Once the minimum systolic volume was reached, a rapid increase of the right ventricular volume started. The right ventricular pressure-volume loop, unlike the left ventricular one, adopted a non-rectangular shape. The right ventricular ejection period lasted until the beginning of the next filling phase. We concluded that there is no right ventricular isovolumic relaxation period.