Sensitivity and specificity of echocardiographic diagnosis of pericardial effusion.

In order to evaluate the reliability and sensitivity of echocardiograms for detecting and quantitating pericardial effusion, 41 patients had echocardiograms on the day prior to cardiac operation. A fluid trap was used to aspirate the pericardium at operation. Thirty-nine of 41 patients had echocardiograms of diagnostic quality. In 25 patients, the echocardiogram was negative for pericardial effusion, with 0-16 ml identified at operation. In 13 patients, the echocardiogram was positive for pericardial effusion, with 15-775 ml aspirated at operation. A transition of patterns of relative posterior epicardial-pericardial movement was noted as the pericardial fluid volume increased. More than 15 ml was always found when a posterior echo-free space persisted throughout the cardiac cycle between a flat pericardium relative to the epicardium. In the presence of such a posterior echo-free space, a large anterior echo-free space made a moderately large pericardial effusion likely. In the absence of this diagnostic posterior echo-free space, an anterior echo-free space had no diagnostic significance, as it was found in 11 patients with less than 16 ml of pericardial effusion. A small posterior echo-free space persisting throughout the cardiac cycle between pericardial and epicardial echoes demonstrating virtually identical movements was found in two patients without any surgical evidence for pericardial effusion, but with evidence of adhesive fibrocalcific pericardial disease. A method of estimating pericardial volume is proposed, which uses the difference between the cubed diameters at the end-diastole of the pericardium and epicardium.