A 72-year-old man presents with shortness of breath that awakens him at night. He is unable to walk more than one city-block before stopping to catch his breath. Physical examination findings include normal blood pressure, bilateral basilar rales, and neck vein distention. The patient has diabetes and a known history of congestive heart failure. His last echocardiogram revealed a left ventricular ejection fraction of 25%. The patient has compliant with his medication regimen that includes an ACE inhibitor, beta-blocker, a loop diuretic, metformin, and glipizide. What is the most likely etiology for the patient’s heart failure?
A. MetabolicCoronary artery disease has become the predominant primary cause of congestive heart failure in industrialized countries, causing 60% to 75% of cases. Coronary artery disease, hypertension, and diabetes mellitus interact to augment the risk of heart failure in many patients, but coronary artery disease is the primary cause in most. In 20% to 30% of patients the exact etiology is not known. These patients are referred to as having nonischemic, dilated, or idiopathic cardiomyopathy. Prior viral infection or toxins (eg, alcohol or chemotherapy) may also lead to a dilated cardiomyopathy. Specific genetic defects such as mutations of genes encoding cytoskeletal proteins (desmin, cardiac myosin, vinculin), and nuclear membrane proteins (lamin) have been identified that may cause dilated cardiomyopathy. The condition is also associated with Duchenne, Becker, and limb girdle muscular dystrophies. Conditions that lead to a high cardiac output (eg, arteriovenous fistula, anemia) are seldom solely responsible for the development of heart failure.