Pericardial modulation of right and left ventricular diastolic interaction.

We studied the effects of the right ventricle (RV) and pericardium on left ventricular (LV) diastolic pressure-volume (P-V) relations in the normothermic isolated blood-perfused dog heart. Studies were performed at a constant heart rate (atrial pacing at 120 beats/min) with a coronary perfusion pressure of 100 mm Hg. LV volume was directly controlled by an intraventricular balloon, whereas RV filling pressure was increased stepwise from zero to 20 mm Hg. During progressive increases in RV filling pressure, with the pericardium intact, the LV diastolic P-V relations were shifted up and to the left; this leftward shift of the LV diastolic P-V relation was associated with an increase in the modulus of LV chamber stiffness. Closing the small pericardial incisions with sutures significantly increased this effect. In the absence of the pericardium, progressive filling of the RV resulted in minor changes in LV diastolic P-V relations. Only when the RV filling pressure was markedly elevated (20 mm Hg) was there a significant effect on LV diastolic pressure. The pericardium has a small but significant effect on LV diastolic P-V relations at physiological RV filling pressures, and this effect becomes considerable at high RV filling pressures. The RV influence on LV diastolic P-V relations is significantly modulated by the presence of tightness of the pericardium.