A 73-year-old woman with a history of dyspnea on exertion presents for a follow-up visit after hospitalization for acute worsening of dyspnea and orthopnea. On admission to the hospital, the patient had atrial fibrillation with a ventricular rate of 120 beats per minute, and chest radiography revealed pulmonary venous hypertension. Despite anticoagulation, rate control with a beta-blocker, and administration of loop diuretics during the hospitalization, she continues to have fatigue and exertional dyspnea. On physical examination, the body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) is 39, pulse 76 beats per minute, and blood pressure 160/70 mm Hg. There is jugular venous distention and lower-extremity edema but no third heart sound, murmurs, or rales. The serum creatinine level is 1.4 mg per deciliter (124 mu mol per liter), estimated glomerular filtration rate (GFR) 37 ml per minute per 1.73 m(2) of body-surface area, and N-terminal pro-brain natriuretic peptide (NT-proBNP) level 300 pg per milliliter (age-specific and sex-specific normal range, 10 to 218 pg per milliliter). Echocardiography reveals an ejection fraction of 70%, a normal left ventricular cavity dimension and wall thickness, and left atrial enlargement. Doppler echocardiography shows elevated left atrial pressure (E/e' ratio, 22) and an estimated pulmonary-artery systolic pressure of 52 mm Hg. How should this patient's condition be managed?