[Assessment of interaction between the left and right ventricles using pressure-volume loops in various heart diseases].

To assess the interaction and interdependence of left and right ventricular function, ECG-gated radionuclide angiocardiography was performed immediately after cardiac catheterization during right atrial pacing for 11 patients with old myocardial infarction (MI), two with non-obstructive hypertrophic cardiomyopathy, one with aortic stenosis (AS), two with pulmonary infarction (PI), and one with neurocirculatory asthenia (NCA). Absolute left ventricular (LV) volume curves were obtained by the count-based method with attenuation factor corrections. Biventricular pressure and volume curves were digitized and synchronized to end-diastole, and pressure-volume (P-V) loops were constructed throughout a cardiac cycle. The stroke work index (SWI), the work index per min (WI/M) and the contractility index (CNTI) were calculated from the P-V loops. In a patient with NCA, LV end-diastolic volume decreased during rapid pacing, but no significant change in the LV end-systolic P-V relation was recognized. However, the entire right ventricular (RV) P-V loop was shifted toward the left during rapid pacing. In a patient with AS, the LV P-V loop was markedly enlarged and every parameter of LV function was much greater than that of the right ventricle due to increased LV afterload. The areas of RV P-V loops in two patients with PI were larger than those of other patients, because RV pressure was relatively high, and RV volume was increased. It is suggested that RV pressure and volume overloads prevail in patients with PI. In four MI patients with three vessel disease and having collateral circulation, the LV end-systolic P-V relationship was shifted toward the lower right, and every parameter (SWI, WI/M, CNTI) of LV function decreased by rapid pacing. Myocardial ischemia may be induced by rapid pacing stress, causing decreased LV contractility. It was concluded that the P-V loops obtained by RNA and catheterization are clinically useful for estimating the interaction and interdependence between right and left ventricular hemodynamics.