Right ventricular dysplasia vs idiopathic dilated cardiomyopathy

Dilated cardiomyopathy and right ventricular dysplasia, although their aetiologies are unknown, are separate entities which can be recognized by endomyocardial biopsy (EMB) and differentiated from other heart muscle diseases. Biventricular EMB is the most appropriate approach for the diagnosis. Histological definition is relevant to establish prognosis and treatment and for research purposes. Idiopathic dilated cardiomyopathy (CMD) is a heart muscle disease of unknown cause'1', which is recognized by ventricular dilation and a low ejection fraction. In most patients, the left ventricle is clinically and pathologically'2 ' the more severely affected; however, several cases of predominantly right-sided CMD have been reported'3'. Histology consists of regularly arranged, hypertrophied and usually attenuated myocar-dial fibres, covered by a thickened endocardium showing prominence of the smooth muscle component (Fig. 1). Cardiocytes present de-generative changes of various degrees which are better evidenced by electron microscopy where loss of contractile elements, presence of myelin bodies and mitochondriosis with fragmentation of mitochondrial membranes, are found'4'. Increased chronic inflammatory cells are also present in the interstitium and support the immune-infectious mechanism which has been hypothesized in the pathogenesis15'. Indeed, in patients with CMD, evidence of immunological imbalance (presence of anti heart antibodies'6"7', and decreased activity of T-suppressor lymphocytes'8"9') has been documented together with serological (increased titres vs coxsackie B virus110') and myocardial findings (identification of coxsackie B-specific RNA in biopsy samples1"') of virus infection. Right ventricular dysplasia (RVD) is an entit