One complication of pericarditis is pericardial effusion. Sudden onset of pericardial effusion may lead to tamponade. This sudden addition of fluid increases pericardial pressure to the level of right atrial and ventricular pressures, causing chamber collapse and inadequate filling. Physical findings consistent with tamponade include elevated jugular venous pressure, hypotension, paradoxical pulse, and muffled heart sounds. A second complication of pericarditis is fibrosis resulting in constrictive pericarditis. In constrictive pericarditis, early diastolic filling is normal, but the filling is suddenly stopped by the nonelastic fibrotic pericardium. This cessation of filling is probably responsible for the diastolic knock classically heard in this disease. In addition, because of the limited flow into the heart, systemic and, therefore, jugular venous pressures are elevated. The Kussmaul sign may also be present (ie, inappropriate increase in jugular venous pressure with inspiration). Finally, elevated systemic venous pressures can lead to accumulation of in the liver and intraperitoneal space, resulting in hepatomegaly and ascites.