Influence of the pericardium and ventricular interdependence on left ventricular diastolic and systolic function in patients with heart failure.

The pericardium, because of the nature of its pressure-volume relation, can influence left ventricular diastolic and systolic pump function. During an acute increase in heart size that results in the stretching of the pericardium, the elastic properties of the pericardium restrict further cardiac dilatation and curtail the ability of the ventricles to increase stroke volume. In addition, the pericardium enhances the degree to which increments in right ventricular volume would alter left ventricular diastolic distensibility. Ventricular interdependence is enhanced as a direct consequence of pericardial elastic properties. During the heightened venous return associated with marked muscular work, we found evidence of pericardial constraint in 31 of 61 patients with heart failure of varying severity and diverse etiology. The occurrence of pericardial constraint, which was characterized by stroke volume becoming invariant and an equivalent rise in right atrial and pulmonary capillary wedge pressures as work load was raised during incremental upright exercise, was independent of the degree to which maximum oxygen consumption was reduced or, equivalently, the severity of heart failure. In contrast, when pericardial constraint was not apparent during our exercise protocol, stroke volume did not become invariant, and the increments in pulmonary capillary wedge pressure were two- to threefold that of right atrial pressure. Thus, the pericardium can have a substantial role in determining the limits to left ventricular diastolic and systolic function.