[Studies on alteration in biventricular dimensions during stepped elevation in pulmonary arterial pressure with...

A new method for inserting ultrasonic crystals into the interventricular septum (IVS) of dogs was performed to measure the right and left ventricular septum-to-free wall dimensions (RVD, LVD) in a line. The advantage of this technique is minimal damage of the pericardium and no damage of the ventricular wall. The segmental lengths in the right and left ventricles (RVSL, LVSL) were also measured. Stepped elevation of pulmonary arterial pressure induced by ligation of pulmonary arterial branches caused an increase in RVD and a decrease in LVD. IVS shifted to the left and transseptal pressure gradient was reduced. RVD and RVSL increased and percent shortening in RVD and RVSL during ejection decreased with pulmonary hypertension. Although the change in RVD and RVSL basically related each other, those changes in RVD was more evident than in RVSL. Thus, the measurement of RVD and RVSL is indispensable for investigating the right ventricular function. There was a high correlation between the stroke volume and the shortening in RVD (expressed as percent of the control value, respectively) during ejection in pulmonary hypertension (F = 13.88 greater than F 1(20)(0.005) = 9.94), therefore we speculate that right ventricular bellows action is essential in blood ejection from the right ventricle. Furthermore the stroke volume decreased as the shortening in RVSL during ejection decreased (F = 3.17 greater than F 1(20)(0.1) = 2.97), therefore shortening in RVSL is thought to be an important factor causing bellows action, however further investigation is necessary.