Pericardial effusion, tamponade, and constriction

Normally, the intrapericardial space between the two pericardial layers contains 25-50mL serous fluid secreted by the visceral pericardium and the intrapericardial pressure is equal to the intrapleural pressure. The pericardium provides mechanical protection for the heart and lubrication to reduce friction between the heart and contiguous structures. Because of the relative lack of distensibility, the pericardium also exerts hemodynamic impact on cardiac function. It limits acute distention of the heart and contributes to diastolic interaction between the two ventricles (the distention of one ventricle affects the filling dynamics of the other).