Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of Cardiomyopathies

A classification serves to bridge the gap between ignorance and knowledge.¹ Previously the cardiomyopathies were defined as “heart muscle diseases of unknown cause” and were differentiated from specific heart muscle disease (of known cause).² With increasing understanding of etiology and pathogenesis, the difference between cardiomyopathy and specific heart muscle disease has become indistinct. The original classification described three types, which have become established clinical entities, and this terminology has been preserved. The cardiomyopathies are now classified by the dominant pathophysiology or, if possible, by etiological/pathogenetic factors.

Definition and Classification

Cardiomyopathies are defined as diseases of the myocardium associated with cardiac dysfunction. They are classified as dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy.

Dilated Cardiomyopathy

Dilated cardiomyopathy is characterized by dilatation and impaired contraction of the left ventricle or both ventricles. It may be idiopathic, familial/genetic, viral³⁴⁵ and/or immune,⁶⁷ alcoholic/toxic, or associated with recognized cardiovascular disease in which the degree of myocardial dysfunction is not explained by the abnormal loading conditions or the extent of ischemic damage (see below). Histology is nonspecific. Presentation is usually with heart failure, which is often progressive. Arrhythmias, thromboembolism, and sudden death are common and may occur at any stage.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is characterized by left and/or right ventricular hypertrophy, which is usually asymmetric and involves the interventricular septum.⁸ Typically, the left ventricular volume is normal or reduced. Systolic gradients are common. Familial disease with autosomal dominant inheritance predominates. Mutations in sarcomeric contractile protein genes cause disease.⁹ Typical morphological changes include myocyte hypertrophy and disarray surrounding areas of increased loose connective tissue. Arrhythmias and premature sudden death are common.¹⁰

Restrictive Cardiomyopathy

Restrictive cardiomyopathy is characterized by restrictive filling and reduced diastolic volume of either or both ventricles with normal or near-normal systolic function and wall thickness. Increased interstitial fibrosis may be present. It may be idiopathic or associated with other disease (eg, amyloidosis; endomyocardial disease with or without hypereosinophilia).

Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy is characterized by progressive fibrofatty replacement of right ventricular myocardium, initially with typical regional and later global right and some left ventricular involvement, with relative sparing of the septum.¹¹ Familial disease is common, with autosomal dominant inheritance and incomplete penetrance; a recessive form is described. Presentation with arrhythmias and sudden death is common, particularly in the young.¹²

Unclassified Cardiomyopathies

Unclassified cardiomyopathies include a few cases that do not fit readily into any group (eg, fibroelastosis, noncompacted myocardium, systolic dysfunction with minimal dilatation, mitochondrial involvement).

Some diseases may present with features of more than one type of cardiomyopathy (ie, amyloidosis, systemic hypertension). It is recognized that arrhythmias and conduction disease may be primary myocardial disorders. At this time, however, it was elected not to include them as cardiomyopathies.

Specific Cardiomyopathies

The term specific cardiomyopathies is now used to describe heart muscle diseases that are associated with specific cardiac or systemic disorders. These were previously defined as specific heart muscle diseases.

Ischemic cardiomyopathy presents as a dilated cardiomyopathy with impaired contractile performance not explained by the extent of coronary artery disease or ischemic damage.

Valvular cardiomyopathy presents with ventricular dysfunction that is out of proportion to the abnormal loading conditions.

Hypertensive cardiomyopathy often presents with left ventricular hypertrophy in association with features of dilated or restrictive cardiomyopathy with cardiac failure.

Inflammatory cardiomyopathy is defined by myocarditis in association with cardiac dysfunction. Myocarditis is an inflammatory disease of the myocardium and is diagnosed by established histological, immunological, and immunohistochemical criteria. Idiopathic, autoimmune, and infectious forms of inflammatory cardiomyopathy are recognized. Inflammatory myocardial disease is involved in the pathogenesis of dilated cardiomyopathy and other cardiomyopathies, eg, Chagas’ disease, HIV, enterovirus, adenovirus, and cytomegalovirus.¹³

Metabolic cardiomyopathy includes the following categories: Endocrine, eg, thyrotoxicosis, hypothyroidism, adrenal cortical insufficiency, pheochromocytoma, acromegaly, and diabetes mellitus; familial storage disease and infiltrations, eg, hemochromatosis, glycogen storage disease, Hurler’s syndrome, Refsum’s syndrome, Niemann-Pick disease, Hand-Schüller-Christian disease, Fabry-Anderson disease, and Morquio-Ullrich disease; deficiency, eg, disturbances of potassium metabolism, magnesium deficiency, and nutritional disorders such as kwashiorkor, anemia, beri-beri, and selenium deficiency; amyloid, eg, primary, secondary, familial, and hereditary cardiac amyloidoses, familial Mediterranean fever, and senile amyloidosis.

General system disease includes connective tissue disorders, eg, systemic lupus erythematosus, polyarteritis nodosa, rheumatoid arthritis, scleroderma, and dermatomyositis. Infiltrations and granulomas include sarcoidosis and leukemia.

Muscular dystrophies include Duchenne, Becker-type, and myotonic dystrophies.

Neuromuscular disorders include Friedreich’s ataxia, Noonan’s syndrome, and lentiginosis.

Sensitivity and toxic reactions include reactions to alcohol, catecholamines, anthracyclines, irradiation, and miscellaneous. Alcoholic cardiomyopathy may be associated with a heavy alcohol intake. At present we cannot define a causal versus a conditioning role of alcohol or apply precise diagnostic criteria.

Peripartal cardiomyopathy may first manifest in the peripartum period. This is probably a heterogeneous group.

P.Nordet,MD \

Footnotes