cardiomyopathias

Cardiomyopathies are diseases of the heart muscle in which the myocardium becomes structurally and functionally abnormal, not explained by coronary artery disease, valvular disease, or abnormal loading conditions. They are a heterogeneous group that collectively cause heart failure, arrhythmias, and, in some cases, sudden cardiac death. The term is used for both primary myocardial diseases and conditions in which myocardial disease is part of a systemic disorder.

Classification commonly distinguishes primary cardiomyopathies from secondary ones, with main morphologic categories including dilated cardiomyopathy (dilation and impaired systolic function of one or both ventricles), hypertrophic cardiomyopathy (thickened ventricular walls, often with preserved or reduced function), restrictive cardiomyopathy (impaired ventricular filling with normal or near-normal systolic function), arrhythmogenic right ventricular cardiomyopathy (fibrofatty replacement of the right ventricle leading to arrhythmias), and left ventricular noncompaction. Some conditions overlap or lie outside these categories and are labeled unclassified.

Etiology ranges from genetic mutations in sarcomeric, cytoskeletal, and desmosomal proteins to acquired factors such as alcohol or toxin exposure, viral myocarditis, autoimmune disease, metabolic abnormalities (thyroid disease, iron overload), and peripartum changes. Genetic forms commonly involve autosomal dominant inheritance with variable expressivity; many patients harbor pathogenic variants in multiple genes.

Clinical presentation varies from asymptomatic to signs of heart failure, chest pain, syncope, or sudden cardiac death due to arrhythmias. Diagnosis relies on history, imaging (chiefly echocardiography, with cardiac MRI in selected cases), ECG, biomarker testing, and, when indicated, genetic testing and endomyocardial biopsy.

Management emphasizes symptom relief and risk reduction, using guideline-directed heart failure therapies when appropriate, disease-specific interventions (such as septal reduction or ICD for certain hypertrophic or arrhythmogenic forms), and consideration of heart transplantation in advanced disease. Prognosis is highly variable and depends on the subtype and associated factors.