Prevalence of Viral Myocarditis

I wish to comment on the interesting article by Greaves et al¹ on the prevalence of myocarditis during acute viral infections, in which they concluded that the prevalence of myocarditis during acute influenza infection is low. I, too, had always questioned the frequency and diagnosis of viral myocarditis till I visited Berlin recently.²

As a visiting professor, I made rounds with the staff at the Charité (French for charity), the teaching hospital of Humboldt University Medical Faculty and the oldest hospital in Berlin, and was surprised at the frequency of diagnosis of acute myocarditis made in any patient admitted with cardiac arrhythmias, congestive heart failure, or abnormal electrocardiograms. In the United States the diagnosis of myocarditis would seldom be made in these patients because of difficulty in confirming such a diagnosis without a myocardial biopsy. But the diagnosis of most of these patients I saw in Charité would be confirmed by serial electrocardiograms (ST changes, atrioventricular block, and various arrhythmias), echocardiograms (reduced left ventricular function), and elevated creatine kinase and positive troponin T levels as well as nuclear studies (positive antimyosin antibody scintigraphy and positive contrast media–enhanced magnetic resonance imaging).³