Atrial fibrillation during labor unmasking a large left atrial myxoma

Cardiac myxomas are the most common primary cardiac tumors and may remain clinically silent until hemodynamic stress precipitates symptoms. Presentation with newonset atrial fibrillation during labor is exceptionally uncommon and may reveal previously undiagnosed structural heart disease. A 39yearold primigravida with no previous cardiovascular history developed newonset atrial fibrillation with rapid ventricular response during labor. Maternal hemodynamics remained stable, and assisted forceps delivery was successfully performed without maternal or neonatal complications. Transthoracic echocardiography demonstrated a large left atrial mass attached to the interatrial septum, measuring 17.3 cm². Computed tomography confirmed a 5.4×5.0 cm left atrial tumors adjacent to, but not involving, the left pulmonary vein ostia, consistent with atrial myxoma. The patient was commenced on apixaban and betablocker therapy before elective surgical resection three months postpartum. Histopathological examination confirmed atrial myxoma. Postoperative recovery was uncomplicated, with complete tumor excision and preserved left ventricular systolic function. Persistent atrial fibrillation was successfully treated with elective directcurrent cardioversion nine months after surgery, restoring sinus rhythm. This case highlights labor as a potential trigger for the clinical manifestation of previously asymptomatic intracardiac tumors. Newonset atrial fibrillation during pregnancy or labor should prompt early echocardiographic assessment to exclude structural cardiac disease. Timely diagnosis and surgical excision of atrial myxoma are essential to prevent lifethreatening complications, including systemic embolization, valvular obstruction, and recurrent arrhythmias, while ensuring excellent longterm outcomes.