Further echocardiographic observations in pericardial effusion.

Although the presence of fluid behind the left atrium, on echocardiography, has been used to differentiate pleural from pericardial effusions, five cases are reported showing that pericardial fluid can and does accumulate behind the left atrium. Abnormal valvular motion, as a result of free swinging of the heart in the pericardial sac, was also demonstrated in these patients.