LOW-FREQUENCY OF DETECTION BY NESTED POLYMERASE CHAIN-REACTION OF ENTEROVIRUS RIBONUCLEIC-ACID IN ENDOMYOCARDIAL TISSUE OF PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

Objectives. The purpose of this study was to determine the prevalence of enteroviral infection in the myocardium of patients with idiopathic dilated cardiomyopathy by using a highly sensitive and specific detec tion technique. Background. Recent molecular studies have suggested th at enteroviral persistence (in particular, coxsackieviruses type B) ma y underlie idiopathic myocarditis and dilated cardiomyopathy. Methods. The method used to detect enterovirus-specific ribonucleic acids (RNA s) is based on reverse transcription and nested polymerase chain react ion amplification with four pairs of primers from the conserved 5' non coding region of the enteroviral genome. Several members of the Entero virus genus are detectable by this assay (coxsackieviruses B1 to B6; p olioviruses 1 to 3; echoviruses 9, 19 and 31), with a sensitivity thre shold close to the detection of a single molecule of viral RNA in 1 mg of tissue sample. Endomyocardial tissue samples from 84 subjects were analyzed (77 samples obtained from left endomyocardial biopsies, 7 fr om explanted hearts). The subjects comprised 63 study patients (53 wit h dilated cardiomyopathy, 3 with idiopathic myocarditis, 1 with right ventricular dysplasia, 1 with restrictive cardiomyopathy, 1 with eosin ophilic myocarditis, 1 with primary ventricular fibrillation and 3 wit h myocarditis of known etiology) and 21 control subjects with other di seases. Results. Positive signals were obtained only in samples from s ix study patients (four with dilated cardiomyopathy, one with right ve ntricular dysplasia and one with myocarditis). Samples from control su bjects, uninfected rat myocardium and cultured cell lines yielded syst ematically negative results. Moreover, the nucleotide sequence analysi s of the amplification products from patients with positive samples ra ised doubts about the true positivity of these samples. Conclusions. T his study suggests that the persistence of enteroviral RNA in dilated cardiomyopathy is not a major cause of the disease and that a careful analysis of polymerase chain reaction amplification products is essent ial in any study in which this technique is pushed to high sensitivity thresholds.