Fibrinous material in a pericardial effusion mimicking intraatrial thrombus

A 74-year-old woman presented with an acute cerebrovascular infarct involving multiple vascular territories, suggestive of an embolic event. The initial transesophageal images create the impression of an echogenic mass in the left atrial appendage. A small pericardial effusion was also seen surrounding the left atrial appendage. After further views were obtained, the echogenic mass appeared to be in this fluid-filled space rather than in the appendage itself. To confirm this finding, echo contrast (Definity) was administered. After contrast injection, the left atrial appendage was opacified, while the effusion around the appendage and the echodensity within this space were not opacified. Our case highlights the utility of contrast-enhanced echocardiography in clearly delineating the boundaries of the endocardium in cases, when a pericardial effusion surrounds the left atrial appendage.