Dynamic right and left ventricular interactions in the pig

Abstract

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 pentobarbitoneanaesthetized 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 endsystolic 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.

Increasing Levels of Positive End-expiratory Pressure Cause Stepwise Biventricular Stroke Work Reduction in a Porcine Model

“…36 The importance of an external constrain for the transseptal pressure gradient is discussed elsewhere. 37,38 Pinsky 38 showed that increased right ventricular systolic pressure did not affect systolic ventricular interdependence, supporting our observations of unaltered left ventricular ejection fraction and end-systolic pressure-volume relationship.…”

“…The transseptal pressure gradient also decreased. This may affect diastolic ventricular interdependence, 38 and may be a part of the explanation of our observations on tau for both ventricles concomitant with the reduced end-diastolic volume and end-diastolic pressure, especially for the right ventricle.…”

Impact of sternotomy and pericardiotomy on cardiopulmonary haemodynamics in a large animal model

“…Pericardiotomy trended to cause LV dilatation, as shown significantly previously (Angelini et al, 1990) on the pre-interventional situation, which confirms previous findings (Pinsky, 2020). Likewise, interventricular dependence has been shown…”

“…The physiological effects of cardiac constraint by the pericardium, lungs and chest wall and how the removal of an external constraint will reduce the impact of any intervention of interest have been discussed for decades (Belenkie et al., 2004 ; Butler, 1983 ; Lloyd, 1982 ; Pinsky, 2020 ; Pinsky et al., 1983 ), supporting our aim of quantifying the changes on modern cardiovascular equipment in order to improve rigorous reporting. Furthermore, we emphasize the importance of researchers choosing a clinically relevant animal model (open vs. closed chest) mimicking their field of interest, but we cannot provide a single best model for specific cardiac disease paradigms.…”

“…The physiological effects of cardiac constraint by the pericardium, lungs and chest wall and how the removal of an external constraint will reduce the impact of any intervention of interest have been discussed for decades (Belenkie et al, 2004;Butler, 1983;Lloyd, 1982;Pinsky, 2020;Pinsky et al, 1983) models lacking the external cardiac constraint (Belenkie et al, 2004).…”