Echocardiogram showing right atrial thrombus in a patient with prior atriopulmonary Fontan operation

Still-frame two-dimensional apical transthoracic echocardiographic image in a patient with prior atriopulmonary Fontan operation. The patient presented with atrial arrhythmias and was noted to have dilation of the right atrium and a large (5.1 x 3.9 cm) thrombus (asterisk) in the right atrium.