Hypertrophic Cardiomyopathy in Infants and Children

The definition and classification of the cardiomyopathies has been traditionally a complex and quite variable subject. In 2006, the American Heart Association issued a scientific statement elaborated by a task force of experts that contemplated the important development of molecular genetics in recent years, to explain the etiology of the diseases of cardiac muscle, or cardiomyopathies, previously considered idiopathic (B.J. Maron et al., 2006a). The document stated that “Cardiomyopathies are an heterogeneous group of myocardial diseases associated with mechanical and/or electrical dysfunction that usually, but not always, exhibit inappropriate ventricular hypertrophy or dilation, and are originated by a variety of causes, frequently genetic. Cardiomyopathies involve just the heart or are part of systemic disorders that often lead to cardiovascular death or heart failure related disability”. Myocardial damage secondary to coronary atherosclerosis, heart valve disease, congenital heart disease, and systemic hypertension, is excluded from this definition. Primary or metastatic cardiac tumors and diseases primarily affecting the endocardium with minimal or absent myocardial damage neither are included. The document also discourages the use of the classical terminologies hypertrophic, dilated, and restrictive cardiomyopathies because they have overlapping features and often mutate from one type to another during the course of the disease. Cardiomyopathies are then classified into 2 groups, primary when there is only heart involvement, and secondary if the heart is affected by systemic diseases with multiorganic involvement. (Table 1) Primary cardiomyopathies are divided into genetic, acquired, and mixed (genetic and acquired).