A 44-year-old woman presents with progressively worsening dyspnea for one week. There is no history of orthopnea, paroxysmal nocturnal dyspnea, chest pain, or cough. She was asymptomatic before this, has no comorbidities, and is not on any medications. There is no history of recent trauma. She has never smoked, and only drinks socially. A complete blood count and electrocardiogram (ECG) are normal.