The 2006 American Heart Association Classification of Cardiomyopathies Is the Gold Standard

The cardiomyopathies are an important and complex group of heart muscle diseases with multiple etiologies and heterogeneous phenotypic expression.1 Awareness and knowledge of these diseases in both the public and medical communities have historically been impaired by periodic confusion surrounding definitions and nomenclature. Therefore, formal and systematic classifications have traditionally been viewed as useful exercises promoting greater understanding of the heart muscle diseases.1–10 Indeed, a multitude of such cardiomyopathy classifications have been advanced over the years by individual investigators and consensus panels sanctioned by medically related organizations such as the World Health Organization (WHO).2,4 These classification schemes have evolved in concert with the level of scientific understanding. Response by Elliott p 76 Remarkably, it was not until 50 years ago (1957) that the term cardiomyopathy was used for the first time.1 Over the next 25 years, a number of definitions for cardiomyopathies were advanced. Indeed, in the original 1980 WHO classification,4 cardiomyopathies were defined only as “heart muscle diseases of unknown cause,” reflecting a general lack of available information about basic disease mechanisms. In 1968, the WHO defined cardiomyopathies as “diseases of different and often unknown etiology in which the dominant feature is cardiomegaly and heart failure.”1,3 The final WHO classification published in 19952 proposed “diseases of myocardium associated with cardiac dysfunction” and included for the first time arrhythmogenic right ventricular cardiomyopathy/dysplasia, as well as primary restrictive cardiomyopathy. Therefore, why was it necessary to offer yet another classification scheme for cardiomyopathies in 2006 under the auspices of the American Heart Association (AHA)1? In fact, the international expert consensus panel (and writing group) found several very important reasons to take on this project. The last formal effort at developing a consensus for the classification of cardiomyopathies had been published 12 years previously …