Prominent crista terminalis: as an anatomic structure leading to atrial arrhythmias and mimicking right atrial mass.

Crista terminalis is a fibromuscular ridge at the posterolateral region of the right atrium (RA). Superiorly localized prominent crista terminalis can mimic pathologic RA mass on transthoracic echocardiograms. Transesophageal echocardiography can be used to differentiate nonpathologic structures from pathologic ones. Besides mimicking RA mass, crista terminalis is an important anatomic structure responsible for paroxysmal atrial fibrillation and atrial flutter by initiating ectopic atrial beats. In this case we discuss a patient with atrial arrhythmias who had prominent crista terminalis misdiagnosed as RA mass.