Dilated cardiomyopathy overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-in-Chief: Sachin Shah, M.D.
Overview
Dilated cardiomyopathy is a condition of the heart that causes dilation and impaired contraction of the left ventricle (or both ventricles). Impaired contraction is defined as a low ejection fraction (< 40%).
Pathophysiology
Familial traits and mitochondrial inheritance are thought to play a part in the development of idiopathic dilated cardiomyopathy, and the inheritance occurs in an autosomal dominant pattern. Connective tissue disease, and other diseases or toxins that disrupt the tissue of the heart are also implicated in the development of dilated cardiomyopathy.
Causes
There are many causes of dilated cardiomyopathy. The most common cause is idiopathic in 50% of cases. The next most common cause is myocarditis which is responsible for 10% of cases. Other common causes include substance abuse, connective tissue disease, pregnancy, medications, nutritional deficiencies, infiltrative diseases and toxins.
Epidemiology and Demographics
Dilated cardiomyopathy is most likely to occur between the ages of 20-60, is three times as likely to occur in males over females, and is 2.5 times more likely to occur in African Americans.
Natural History, Complications and Prognosis
There are several prognostic indicators when evaluating dilated cardiomyopathy, the most important one being ejection fraction. Complications as a result of dilated cardiomyopathy include heart failure, aortic and mitral valve regurgitation, emboli, edema, arrhythmias and sudden cardiac arrest.
Diagnosis
History and Symptoms
Common symptoms in the setting of dilated cardiomyopathy include chest pain, cough, fatigue, loss of appetite, and shortness of breath. A careful history is important in the setting of dilated cardiomyopathy in order to ascertain the etiology of the cardiomyopathy. The patient needs to be evaluated for a history of coronary artery disease, viral prodrome and infections, chemotherapy, HIV risk factors, pregnancy, medications, toxins, and substance abuse.
MRI
In patients presenting with heart failure, where the etiology of the cardiac dysfunction is unclear, cardiac MRI can be a useful imaging modality. It can be used to distinguish the area of inflammation, to help in the diagnosis of myocarditis, to evaluate patients with suspected infiltrative diseases, and to evaluate dilated cardiomyopathy in the setting of normal coronary arteries.
Echocardiography
Echocardiography is the most common imaging finding used to diagnose dilated cardiomyopathy. Findings may include ventricular and atrial dilatation, increased left ventricular mass, a global reduction in systolic function, and focal wall motion abnormalities.
Other Diagnostic Studies
Endomyocardial biopsy has low sensitivy and the findings are also notoriously non-specific. The findings on biopsy usually involve findings of inflammation and specific pathogens are unlikely to be identified. There may be an increased yield to using MRI to target endomyocardial biopsy. Viral titiers (serologies) are often unhelpful and not routinely ordered in clinical practice.
Treatment
Medical Therapy
Treatment should focus on correcting the underlying cause of the cardiomyopathy when possible. Treatment is also targeted towards preventing death, and ameliorating the symptoms of heart failure. Medications that have been proven to reduce mortality in patients with systolic heart failure are; ACE inhibitors, beta blockers, angiotensin II receptor blockers, nitrates, and hydralazine. Diuretics and digoxin are used for symptom relief.