Relationship between the pericardial and pleural spaces in cross-sectional imaging.

Sixty patients, including 15 with large pericardial effusions, five with large left pleural effusions, and nine with both, were studied prospectively with two-dimensional echocardiography to verify the relation of pericardial effusions and posterior paramediastinal pleural effusions to the descending thoracic aorta. It was found that large pericardial effusions lie anterior to the descending aorta both at the level of the left atrium and the left ventricle, whereas large posterior paramediastinal pleural effusions lie posterior, lateral, or posterolateral to the descending aorta. A retrospective study of 148 M-mode echocardiograms showed similar findings; but the descending thoracic aorta was less reliably identified, and the lateral position of pleural effusions with respect to the aorta could not be evaluated.