Cardiomyopathy Basics

Cardiomyopathy is a disorder in which the myocardium is structurally or functionally abnormal and the abnormality cannot be adequately explained by coronary artery disease, hypertension, valvular disease, or congenital heart disease alone. The damaged or altered muscle may pump weakly, relax poorly, become excessively thick, or provide a substrate for dangerous dysrhythmias. Contemporary classification is phenotype-based: - Hypertrophic cardiomyopathy (HCM): disproportionate myocardial thickening, often involving the interventricular septum. - Dilated cardiomyopathy (DCM): ventricular enlargement with impaired systolic contraction. - Non-dilated left ventricular cardiomyopathy (NDLVC): left ventricular myocardial disease without marked chamber dilation, often identified through fibrosis, arrhythmia, or reduced function. - Arrhythmogenic right ventricular cardiomyopathy (ARVC): myocardial replacement by fibrofatty tissue, creating a high-risk ventricular arrhythmia substrate. - Restrictive cardiomyopathy: stiff ventricles that fill poorly despite relatively preserved chamber size; infiltration by amyloid is an important cause. The clinical picture follows the mechanical problem. A dilated ventricle cannot generate an effective stroke volume, so forward flow falls and fluid backs up into the lungs and systemic circulation. A hypertrophied ventricle may contract vigorously but relax poorly; it behaves like a...