The MOGE(S) Classification for a Phenotype-Genotype Nomenclature of Cardiomyopathy: Endorsed by the World Heart Federation
Arbustini, E and Narula, N and Dec, GW and Reddy, KS and Greenberg, B and Kushwaha, S and Marwick, T and Pinney, S and Bellazzi, R and Favalli, V and Kramer, C and Roberts, R and Zoghbi, WA and Bonow, R and Tavazzi, L and Fuster, V and Narula, J, The MOGE(S) Classification for a Phenotype-Genotype Nomenclature of Cardiomyopathy: Endorsed by the World Heart Federation, Journal of the American College of Cardiology, 62, (22) pp. 2046-2072. ISSN 0735-1097 (2013) [Refereed Article]
Copyright 2013 American College of Cardiology Foundation
In 1956, Blankerhorn and Gall (1) proposed the term myocarditis for inflammatory heart muscle disease, and myocardiosis for other heart muscle diseases. A year thereafter, Brigden (2) defined cardiomyopathies as uncommon, non-coronary heart muscle diseases. Subsequently, Goodwin and Oakley (3) defined cardiomyopathies as myocardial diseases of unknown origin, and proposed categorization of the disorders as dilated (DCM), hypertrophic (HCM), and restrictive (or obliterative) (RCM) cardiomyopathies. In 1980, the World Health Organization (WHO) and International Society and Federation of Cardiology (ISFC) established the definition of cardiomyopathies as myocardial diseases of unknown etiology, reflecting the general lack of information about the mechanism(s) of disease (4). Although WHO-ISFC retained the 3 morphological types of cardiomyopathies proposed by Goodwin and Oakley, it also introduced the term specific heart muscle disease, where the cause of myocardial dysfunction was known. The WHO-ISFC classification subsequently expanded the definition of cardiomyopathies by adding the functional component and defined cardiomyopathy as the diseases of myocardium associated with myocardial dysfunction. Two additional classes, arrhythmogenic right ventricular cardiomyopathy (ARVC) and unclassified cardiomyopathy, were introduced during the revision, and the category of the specific heart muscle disease was excluded (5). The ISFC changed its name to the World Heart Federation (WHF) in 1998 (6), and did not indulge in further revision of the recommendations for either diagnosis or management of cardiomyopathies.
A substantial increase in the knowledge of the genetic basis of cardiomyopathy has occurred, and noninvasive phenotypic characterization has become significantly more sophisticated. Therefore, the American Heart Association (AHA) (7) and the European Society of Cardiology (ESC) (8) in the last decade have proposed revisions to the classification of cardiomyopathic disorders. Whereas both systems have substantial similarities and have made important recommendations, the former has described cardiomyopathies starting from the genetic basis of the etiology followed by the phenotypic description of myocardial involvement. Conversely, the ESC has retained the description in original morphofunctional categories with further subclassification into genetic (familial) and nongenetic (nonfamilial) groups. Both classifications continue to exclude specific heart muscle disease (resulting from coronary, hypertensive, valvular, and congenital heart disease) from consideration as a cardiomyopathic disorder.
There is no denying the fact that most cardiomyopathies are genetic diseases, which in the real life are brought to clinical attention (and diagnosed and managed) based on a phenotypic diagnosis. More than 60 disease genes have been identified to date (9); genes such as MYBPC3 may be associated with different phenotypes (HCM, RCM, DCM), and genes such as DYS may cause a unique phenotype (DCM only). The penetrance of the genetic mutation is variable, and phenotypic manifestations are often age dependent. Most genetic cardiomyopathies are inherited as autosomal dominant traits, with a minority of families demonstrating autosomal recessive, X-linked recessive or dominant (rare), and matrilineal inheritance. Cascade family screening and follow-up have become mandatory (10). It has become necessary for a more descriptive nosology to be developed that may encompass either all attributes of the individual patient cardiomyopathy or allow a common platform for collaborative research efforts. A number of experts, including clinical cardiologists, heart failure–transplantation physicians, geneticists, and cardiovascular imagers, have proposed a systematic nomenclature endorsed by the WHF Scientific Committee. The proposed classification is a descriptive presentation of the cardiomyopathic process, which is flexibly modifiable and expandable. This nosology is inspired from the TNM staging of tumors and is being simultaneously published by the Journal of the American College of Cardiology and the official journal of the WHF, Global Heart.