The effects of a pericardial collection are dictated by the finite compliance of the pericardium, whereas the boundaries and compliance of the structures surrounding a mediastinal hematoma are much less predictable. Although the mediastinal hematoma is extrapericardial, it initially may be difficult to differentiate from intrapericardial blood or a loculated pericardial effusion. Right pleural effusion or ascitic fluid can also appear as anterior mediastinal masses when viewed by 2-D echocardiography from a subcostal approach.

The echocardiographer must be meticulous in obtaining multiple views, if possible, to define the relationship of the mass to cardiac chambers, to pulmonary and hepatic veins, and to the inferior vena cava. When attempting to make this distinction, the examiner should note several characteristics of the echocardiographic appearance of the mass. Intrapericardial fluid usually conforms in a concave configuration to the convex epicardial surface, and will often extend to or around the apex of the heart. Extrapericardial masses tend to conform less to the shape of the pericardial contour and may compress adjacent structures including the right ventricle, outflow tract and pulmonary artery. Here
In the setting of blunt chest trauma, the echocardiogram should always be interpreted in context with clinical signs and hemodynamic data when therapeutic decisions are made. Roentgenographic criteria for mediastinal hematoma formation, including a lateral shift in the trachea, enhanced tracheal and bronchial air shadows, and a widened mediastinal silhouette, are helpful when present, as they were in this case. The decision for appropriate therapy rests with accurate differentiation between an intrapericardial or extrapericardial fluid collection. If any uncertainty exists in this setting, or if the clinical data and imaging techniques used cannot confirm the precise nature of the cause of cardiac compression, then surgery is the only appropriate diagnostic and therapeutic intervention. This report emphasizes the utility and ability of standard two-dimensional echocardiography as an adjunctive diagnostic tool in the clinical setting of blunt chest trauma to accurately identify a mediastinal hematoma and the associated anatomic and hemodynamic relationships to the heart and surrounding structures.