Cardiomyopathy Differential

A reduced ejection fraction is a finding, not a complete diagnosis. Dilated cardiomyopathy (DCM) is defined by left-ventricular or biventricular dilatation with systolic dysfunction that is not explained by an abnormal loading condition—such as significant hypertension, coronary artery disease, valvular disease, or congenital heart disease—sufficient to account for the abnormality. The diagnosis therefore requires a phenotype plus exclusion of a sufficient secondary cause; a low EF alone does not establish DCM. The current classification is morpho-functional: - DCM: a dilated ventricle with impaired systolic contraction, often accompanied by global hypokinesis and functional mitral or tricuspid regurgitation. - Hypertrophic cardiomyopathy (HCM): excessive myocardial thickness not explained solely by loading conditions. The thick, relatively stiff ventricle may produce diastolic dysfunction and, when the mitral valve moves toward the septum, dynamic left-ventricular outflow tract obstruction. - Restrictive cardiomyopathy (RCM): impaired myocardial relaxation and filling from a stiff ventricle. EF may remain preserved, while atrial enlargement and systemic venous congestion become prominent. - Arrhythmogenic right-ventricular cardiomyopathy: a myocardial disorder in which ventricular arrhythmias and right-ventricular structural or functional abnormalities may dominate the presentation. -...