Revisiting definition and classification of cardiomyopathies in the era of molecular medicine.

Primary myocardial diseases have always attracted the attention of the scientific community because of their obscure aetiopathogenesis, and for years there was confusion and controversy regarding their nosography and taxonomy. Since the first WHO official classification,1 tremendous progress has been made.2 Novel entities have been discovered, requiring an update of the classification in 1995,3 and the aetiology of many forms has been clarified. The Working Group of Myocardial and Pericardial Disease of the European Society of Cardiology (ESC) recently published a position statement4 different from the 2006 American Heart Association (AHA) scientific statement.5 The scope of the present editorial is to deal with the nosographic impact of the advances made since 1995 and to comment on the ESC position statement which has been designed to provide a valid tool for routine clinical practice. The discovery of novel cardiomyopathies, namely arrhythmogenic right ventricular cardiomyopathy (ARVC), primary restrictive cardiomyopathy, and non-compacted myocardium, made a revision of the 1980 classification compulsory, and this led to many substantial, though often questionable, changes.3 Moreover, taking into consideration that the aetiology was becoming clearer and clearer, the definition was changed from 'heart muscle disease of unknown aetiology' into 'myocardial disease associated with cardiac dysfunction', the term dysfunction meaning both mechanical and electrical abnormality. In the new classification, ARVC6,7 and restrictive cardiomyopathy8 were added to the primary forms, whereas the non-compacted myocardium was left in the limbo of 'unclassified cardiomyopathies'. The secondary forms, which in the classification of the 1980s were called specific heart muscle diseases, were given the name of 'specific cardiomyopathies', and within this group myocarditis was added. Unfortunately, the concept of specific cardiomyopathy was widened too much, so as to include chronic ischaemic, valvular, and hypertensive diseases. Although the 1995 classification made significant contributions … *Corresponding author. Tel: +39 049 8272283, Fax: +39 049 8272284, Email: gaetano.thiene{at}unipd.i