Dynamic right and left ventricular interactions in the pig.

I characterized the dynamic factors determining ventricular interdependence with and without the pericardium. I measured right (RV) and left ventricular (LV) pressures and volumes simultaneously using conductance catheters in seven pentobarbitone-anaesthetized open-chested 5- to 7-week-old piglets. I studied these effects during apnoea, inferior vena caval occlusion and rapid partial aortic and pulmonary arterial occlusions. Conductance catheter-defined long-axis regional volumes were assessed to define regional contractile synchrony. Closed-pericardium measures were made from an initial (baseline) volume, then after two 20 ml kg-1 fluid loads followed by an open-pericardium step. Baseline RV and LV volumes were similar. Aortic occlusion increased LV pressures and volumes and RV end-systolic pressure such that RV end-systolic elastance increased without changes in RV contraction synchrony, not affected by the pericardium. Pulmonary artery occlusion increased RV end-systolic pressure but not end-systolic volume. On the subsequent beat, RV end-diastolic pressure increased, whereas LV end-diastolic volume and diastolic compliance decreased. These effects were attenuated by opening the pericardium. Contraction synchrony across longitudinal segments was unaltered by either aortic or pulmonary artery occlusion. I conclude that the determinants of systolic and diastolic ventricular interdependence are different. Increasing RV pressures causes diastolic RV-to-LV interdependence, decreasing LV diastolic compliance and dependent on an intact pericardium. An increase in LV end-systolic pressure increases RV end-systolic elastance independent of the pericardium and has a minimal effect on RV diastolic function or contraction synchrony.