A 72-year-old female is evaluated in the hospital for a 2-week history of increasing exertional dyspnea and weight gain of 7.3 lbs. Her medical history is significant for idiopathic cardiomyopathy with an ejection fraction (EF) of 25%. What is the most likely cause of the patient's current symptoms? a) Acute exacerbation of heart failure b) Pulmonary embolism c) Pneumonia d) Chronic obstructive pulmonary disease (COPD) exacerbation
