Unmasking cor triatriatum dexter in adult patients with atrial arrhythmia.

Cor triatriatum dexter is a rare congenital cardiac anomaly characterized by persistence of a membranous structure that divides the right atrium into two chambers. Although often asymptomatic, cor triatriatum dexter may present in adulthood with nonspecific symptoms and atrial arrhythmias, including atrial fibrillation and atrial flutter. We present a case series of four adult patients in whom cor triatriatum dexter was incidentally diagnosed during cardiac evaluation for diverse clinical presentations. Patients ranged in age from 51 to 75 years and presented with new-onset seizures, ischemic stroke evaluation, heart failure exacerbation, and recurrent atrial arrhythmias. In all cases, diagnosis was established using echocardiographic imaging, with transesophageal echocardiography providing definitive visualization when transthoracic studies were nondiagnostic. This series highlights the diagnostic challenges of cor triatriatum dexter in adults and suggests that the condition may be underrecognized. Furthermore, altered right atrial anatomy may be associated with atrial arrhythmia maintenance through structural and conduction alterations of the right atrium.