An 18-year-old woman was referred to our adult congenital heart disease center for investigation of chest pain and atrial fibrillation (AF). She had reported intermittent chest pain without precipitating factors since the age of 8 years. This had been evaluated by a pediatric cardiologist and was felt to be noncardiac in nature. Persistence of pain and associated distress eventually prompted referral to adolescent psychiatry. At age 17 years she experienced 3 episodes of AF, each treated with direct-current cardioversion. An electrophysiologist commenced treatment with flecainide and warfarin. Warfarin was stopped after 6 months arrhythmia-free. At our clinic, she reported intermittent, nonexertional, atypical chest pain and exertional dyspnea with a gradual decline in exercise capacity, confirmed by cardiopulmonary exercise test (oxygen consumption peak 65% predicted). Electrocardiogram demonstrated sinus rhythm, a prominent biphasic p-wave, and occasionally prolonged interval between the beginning of the electrocardiographic wave representing ventricular depolarization and the end of the T-wave (QT, QTc up to 594 milliseconds) (Figure 1A). Transthoracic echocardiogram revealed normal ventricular dimensions and systolic function with biatrial dilatation (left > right) (Figure 1B), dilated pulmonary veins, and abnormal diastolic filling. Cardiac magnetic resonance imaging with gadolinium confirmed dilatation of the atria, pulmonary veins, and inferior vena cava with normal ventricular size, mass, and ejection fraction without enhancement suggestive of infarction, inflammation, or fibrosis. Pericardium was of normal thickness. Electrocardiogram A Transthoracic echocardiogram B Figure 1. A, Electrocardiogram demonstrating prominent and biphasic P-wave and ST-T segment abnormalities. B, Four-chamber view of transthoracic echocardiogram. aVF indicates augmented vector foot; aVL indicates augmented vector left arm; and aVR indicates augmented vector right arm. WHAT WOULD YOU DO NEXT? A. Start diuretic, β-blocker, and angiotensin-converting enzyme inhibitor B. Start diuretic, implant cardioverter defibrillator, and evaluate for cardiac transplantation C. Discontinue flecainide, start amiodarone and warfarin D. Proceed with electrophysiology study and AF ablation Clinical Review & Education