The importance of myocardial biopsy in the diagnosis of infectious myocarditis: it still plays a role

This commentary refers to ‘Coronavirus fulminant myocarditis saved with glucocorticoid and human immunoglobulin’, by H. Hu et al., doi: 10.1093/eurheartj/ehaa190. After having read the recent paper by Hu et al.1 describing cardiac involvement in a patient infected by COVID-19, although it is an interesting case report, the investigators only evaluated the presence of myocarditis in one positive COVID-19 patient, concluding that the virus itself could directly cause myocarditis. Indeed, the authors only suggested this as a possibility, but we think that in order to confirm this diagnosis, further certainty data such as endomyocardial biopsy (EMB) should have been used. It is our belief that in the presence of such a particular and unexpected finding, the underlying pathological conditions need to be further examined in order to maintain a more accurate diagnosis. Although the investigators reported fundamental clinical data through the use of diagnostic imaging and also laboratoristic parameters; European Guidelines and several International Studies highlight the fact that, since myocarditis has a great variability in clinical and radiological patterns of presentation, only EMB is able to detect the aetiology, and this is particularly true in cases of viral myocarditis. Cardiovascular magnetic resonance (CMR) imaging alone, does not exclude myocardial infections and moreover, EMB gives us also prognostic information.2 Thus, the combination of CMR and EMB is probably the best option in improving diagnostic sensitivity.3 Based on Caforio et al. papers, ‘a detailed histological, immunohistochemical, and molecular genomic evaluation by EMB has the potential to change the therapeutic strategy’; for example, the exclusion of infectious agents or viral genome in the myocardium is essential for patients who may be candidates for immunosuppressive treatments.4 This author reported also that, based on mouse models, non-specific anti-inflammatory therapy or low-dosage steroids are not recommended in patients without histological confirmation of myocarditis, since they could obstacle virus clearance.5 Middle East respiratory syndrome coronavirus has been associated with acute/fulminant myocarditis and heart failure; thus, it is reasonable to expect similar findings to occur with SARS-CoV-2. We are well aware that EMB has some limitations, and do not want to comment on the potential of COVID-19 as cause of myocarditis. We only want to emphasize the fact that the methodological approach should be based on the current guidelines and protocols. In such a complex historical period, as the one we are living now, it is crucial to follow these guidelines and in this case described by Hu et al., EMB would have added useful and discriminant information, contributing to a more accurate diagnosis and better therapeutic options. Conflict of interest: none declared.