A 39-year-old woman presented with cough and chest pressure and progressively worsening dyspnea over 6 weeks. Further questioning revealed weight loss of 20 lb. She had undergone cholecystectomy 2 weeks earlier; at that time, a grade 3/6 holosystolic murmur was detected. Echocardiographic findings were reported to be normal. She was a former smoker with a 20-pack-year history, had a history of polycystic ovary syndrome and hypertension, and a family history of lung cancer in her father and paternal grandfather. Physical examination on presentation to the emergency department showed BP of 120/60 mm Hg and pulse rate of 87 beats/min. The patient was tachypneic throughout her hospitalization, with a respiratory rate ranging from 20 to 24 breaths/min. The chest was clear to auscultation. Cardiac findings included fixed splitting and prominent pulmonic component of the second heart sound. Laboratory results showed anemia (8.5 g/dL), an elevated d-dimer (4,240 U), Pao2 of 78 mm Hg, Paco2 of 38 mm Hg, and pH 7.49.