Theoretical model of ventricular interdependence: Pericardial effects

One ventricle can influence the filling characteristics of the opposite ventricle directly through the myocardium and indirectly through the pericardium. Based on definitions of compliances and volumes, we developed a theoretical analysis that indicated that the magnitude of interdependence was related to the relative compliances of the left and right ventricular free walls, septum, and pericardium. This analysis was verified in postmortem canine hearts. Balloons were inserted into each ventricle, and left ventricle pressure (ΔP(l)) and volume (ΔV(l)) changes caused by increasing right ventricular pressure (ΔP(r)) and volume (ΔV(r)) or pericardial pressure (ΔP(p)) were recorded. For ΔP(l)/ΔP(r), ΔP(l)/ΔP(p), ΔP(l)/ΔV(r), ΔV(l)/ΔP(r), ΔV(l)/ΔP(p), and ΔV(1)/ΔV(r) measurements, the standard error of estimates was small and the predicted and measured values were significantly related (P < 0.05); the values were 0.88 ± 0.16, 0.87 ± 0.17, 0.93 ± 0.05, 0.95 ± 0.09, 0.96 ± 0.05, and 0.96 ± 0.04, respectively. These coupling coefficients (ΔP(l)/ΔP(r), ΔP(l)/ΔP(p), etc.) a direct measurement of interdependence, indicated that pericardial-to-ventricular coupling is greater than ventricular-ventricular coupling (ΔP(l)/ΔP(p) > ΔP(l)/ΔP(r), 0.91 ± 0.09 vs 0.23 ± 0.09, P < 0.01; ΔV(l)/ΔP(p) > ΔV(l)/ΔP(r), - 1.04 ± 0.35 vs - 0.19 ± 0.05, P < 0.05). This study, by developing a theoretical analysis and by direct measurements, provides a better understanding of ventricular interdependence and may help to predict effects of cardiac tamponade and constrictive pericarditis on ventricular interdepence.