33. Cardiomyopathies and Myocarditis

Cardiomyopathies are diseases of the heart muscle characterized by abnormal chamber size, wall thickness, or functional contractile abnormalities such as systolic or diastolic dysfunction. They include a variety of myocardial disorders that manifest with various structural and functional phenotypes and are frequently genetic. Primary cardiomyopathies consist of disorders that are confined to the heart muscle and are genetic, mixed, and acquired, while secondary cardiomyopathies are caused by myocardial damage from a systemic disease process. The World Health Organization/International Society and Federation of Cardiology task force on the definition and classification of cardiomyopathies has defined five subtypes of cardiomyopathy: dilated, hypertrophic, restrictive, arrhythmogenic right ventricular dysplasia, and unclassified cardiomyopathies. In 2008, the European Society of Cardiology’s working group on myocardial and pericardial diseases presented an update to the WHO/ISFC classification in which cardiomyopathy was defined as “A myocardial disorder in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to explain the observed myocardial abnormality.” Dilated cardiomyopathy is the most common cause, compromising 90 % of cases. Each type of cardiomyopathy has unique etiologies and properties. Treatment is usually directed toward the underlying cause.