Heart muscle disease

Abstract

<h2>Abstract</h2> Primary cardiomyopathies are heart muscle diseases intrinsic to the myocardium. This group includes dilated cardiomyopathy (DCM), arrhythmogenic cardiomyopathy (ARVC), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy (RCM) and unclassified cardiomyopathy. The cardiomyopathies may be classified pathophysiologically and display unique pathological and clinical features. ARVC is characterized by fibroadipose substitution of right ventricular myocardium and a high risk of sudden cardiac death. HCM may be symmetrical or asymmetrical and histologically is associated with widespread myocyte disarray. The clinical presentation and phenotype varies according to which type of myofibrillary gene mutation is responsible for disease. For example, mutations in troponin T carry a poor prognosis and a high risk of sudden cardiac death, whilst mutations in myosin binding protein C are associated with mild disease and onset in middle-age or late adult life. DCM is characterized by an increase in ventricular mass and cavity dilatation with or without thrombi in the atrial appendages. The histological features of DCM are often non-specific but myofibrillary loss, when present, is a helpful diagnostic feature. DCM is the commonest type of cardiomyopathy and most cases are idiopathic. RCM is the least common type of cardiomyopathy and includes diseases that ‘stiffen' the myocardium by fibrosis or infiltration. This group includes Loeffler's endocarditis, tropical endomyocardial fibrosis as well as cardiac amyloidosis and storage disorders. The inflammatory cardiomyopathies include myocarditis, idiopathic giant cell myocarditis and sarcoidosis. Myocarditis has an acute onset and is often accompanied by febrile illness, whereas sarcoidosis has an insidious onset and often presents with heart block.