Potential pitfalls in quantification of pericardial effusions by echocardiography.

In the echocardiographic assessment of patients with pericardial effusions, the apparent width of the echo-free space between the left ventricular posterior wall and the parietal pericardium is commonly used to estimate the amount of pericardial fluid present. In 4 patients with pericardial effusions, we showed a distinct disparity between the widths of the posterior pericardial space at different levels of the left ventricular posterior wall. In 2 of them, a 'swinging heart' appearance was recorded when the ultrasoound beam was directed caudally, but not when its direction was cephalad or less caudad. It is suggested that the left ventricle should be scanned at all possible sites to minimise potential errors in estimating the amount of a pericardial effusion.