A 55-year-old woman from ...

A 55-year-old woman from El Salvador is seen in the emergency department because of gradual onset of dyspnea on exertion. She denies chest pain, cough, wheezing, sputum, or fever. Her chest radiograph is notable for large pulmonary arteries and left atrial enlargement, but no parenchymal infiltrate. ECG shows a tall R in lead V1 and right axis deviation.