A 44-year-old, previously healthy man has experienced worsening exercise tolerance accompanied by markedshortness of breath for the past 6 months. On physical examination, he is afebrile. His pulse is 78/min, respirations are 22/min, and blood pressure is 110/70 mm Hg. He has diffuse rales in all lung fields and pitting edema to the knees. Laboratory studies show serum sodium, 130 mmol/L; potassium, 4 mmol/L; chloride, 102 mmol/L; CO2, 25 mmol/L; creatinine, 2 mg/dL; and glucose, 120 mg/dL. A 100-mL urine sample is collected. There is 1.3 mmol of sodium and 40 mg of creatinine in the urine sample. A chest radiograph shows cardiomegaly and pulmonary edema with pleural effusions. An echocardiogram shows four-chamber cardiac dilation and mitral and tricuspid valvular regurgitation, with an ejection fraction of 30% A coronary angiogram shows less than 10% narrowing of the major coronary arteries. Which of the following is the most likely diagnosis? (A) Rheumatic heart disease (B) Hereditary hemochromatosis (C) Chagas disease (D) Diabetes mellitus (E) Idiopathic dilated cardiomyopathy