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The term cardiomyopathy is used to indicate myocardial dysfunction in the absence of an obstructive lesion or sustained hypertension. Cardiomyopathy is either an isolated abnormality (ie, confined to the heart) or is associated with a multisystem disorder. Neonates who have an unrecognized underlying cardiomyopathy may come to medical attention with a life-threatening response to an otherwise minor illness. Alternatively, evidence of cardiomyopathy may be noted on an echocardiogram performed for evaluation of an unrelated problem.

Mutations in genes encoding multiple proteins of the sarcomere, cytoskeleton, sarcoplasmic reticulum, nucleus, and cell membrane of the myocardial cell are now known to cause cardiomyopathy (Figure 9-1). More information regarding the structure and function of these proteins is available in Chapter 2.

Figure 9-1.

Myocyte cytoarchitecture. Various forms of cardiomyopathy may result from mutations in genes encoding multiple proteins within the cardiac myocyte. Different mutations in the same gene may cause different forms of cardiomyopathy. Abbreviations: EYA4, eyes absent homolog 4; MLP, cardiac LIM domain protein; MYBPC, myosin binding protein C; T-cap, telethonin; ZASP, muscle LIM-binding protein 3 (cypher). Adapted from Olson TM, Hoffman TM, Chan DP. Dilated congestive cardiomyopathy, In: Allen HD, Driscoll DJ, Shaddy RE, Feltes TF, eds. Moss and Adams’ Heart Disease in Infants, Children and Adolescents. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2008:1197.

Classification of cardiomyopathies is problematic and has evolved as new information has become available regarding causation. Classification based on phenotype (ventricular morphology and physiology) is practical in that this information is what is most readily available after initial evaluation of the patient (Table 9-1). Phenotypic groups can be subdivided based on etiology (Tables 9-2, 9-3, 9-4). Some congenital heart defects or systemic hypertension can cause phenotypes that mimic various forms of cardiomyopathy and are included in text and tables as they need to be included in the differential diagnosis when evaluating patients. Phenotypic classification is certainly not perfect as it does not define causation; moreover, it may be misleading because some myopathic processes may be classified as more than one type or may change from one type to another during the course of the disease.

Table 9-1. Phenotypic Classification of Cardiomyopathy
Table 9-2. Conditions Associated with Phenotypic Appearance of Hypertrophic Cardiomyopathy

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