4-chamber view showing circumferential pericardial effusion

The apical 4-chamber view shows a moderate to large anterior and posterior pericardial effusion (PE), but the curvature of the RA is normal. In panel B there is diastolic expiratory invagination, compression, or collapse of the RA. Collapse of the RA is a highly sensitive, but relatively nonspecific, sign of hemodynamically important tamponade. More importantly, the LA also appears compressed. This latter sign is felt to be more specific for tamponade.