Role of pericardial constraint for right ventricular function in humans.

STUDY OBJECTIVE To analyze the extent of pericardial constraint on right ventricular function in humans. PATIENTS AND METHODS Twenty patients, 59 +/- 2 (mean +/- SEM) years old, undergoing coronary bypass surgery. Right ventricular volumes and pressures were evaluated using a rapid response Swan-Ganz thermodilution catheter. INTERVENTIONS Parameters were determined before and after pericardiotomy, both before and during increased right ventricular systolic pressure by partial compression of the pulmonary artery (before pulmonary compression: 25 +/- 1 mm Hg; during: 39 +/- 1 mm Hg). RESULTS Pericardiotomy alone did not significantly affect right ventricular end-diastolic volume (before: 79 +/- 4 mL m-2; after: 78 +/- 3 mL m-2), right ventricular ejection fraction (before: 48 +/- 1%; after: 48 +/- 2%), and right atrial pressure (before: 4.3 +/- 0.8 mm Hg; after: 4.3 +/- 0.7 mm Hg). Before pericardiotomy, the increase in right ventricular afterload significantly increased right atrial pressure (to 5.5 +/- 0.7 mm Hg, p < 0.05) and reduced right ventricular ejection fraction (to 43 +/- 2%, p < 0.01). Right ventricular end-diastolic volume remained unchanged. After pericardiotomy, the increase in right ventricular afterload significantly increased right ventricular end-diastolic volume (to 85 +/- 3 mL m-2, p < 0.01) and also reduced right ventricular ejection fraction (to 42 +/- 2%, p < 0.01), while right atrial pressure was not significantly changed. During increased right ventricular afterload, the right ventricular diastolic pressure-volume relation was shifted rightward. CONCLUSIONS At normal levels of right ventricular diastolic filling, the pericardium does not exert constraining effects on right ventricular function. However, with increasing levels of right ventricular preload, pericardial constraint significantly influences right ventricular function in humans.