Endomyocardial biopsy in patients with myocarditis - still justified in the CMR era? A single-centre experience

Abstract Background Endomyocardial biopsy (EMB) is still considered the diagnostic gold standard for myocarditis. However, in the past decades, cardiac magnetic resonance (CMR) was established as a non-invasive tool supporting the diagnosis of myocarditis. Furthermore, there is often reluctance in performing EMB due to rare but potentially severe complications. We therefore sought to identify patient subgroups that could potentially derive benefits from EMB. This involved a comprehensive analysis of the diagnostic and therapeutic outcomes resulting from the procedure at our centre. Methods In this retrospective single-centre study, data of all patients presenting with (peri-) myocarditis between 01/2016 and 06/2023 at our tertiary care centre were included. Frequency of histological confirmation of acute myocarditis and histology leading to immunosuppressive therapy were analysed according to patient risks. Prespecified risk factors were (i) LV-EF ≤30%, (ii) presence of severe arrhythmias (VF, VT, high grade AV-block) or (iii) pre-existing autoimmune disease. Furthermore, the subgroup of recurrent myocarditis cases was analysed separately. Results A total of 150 consecutive patients (36.7 ± 15.5 years, 77.3% male) were included in this study. 26/150 patients had a documented EF ≤30%, 13/150 an EF >30% with another risk factor and 111/150 an EF>30% without another risk factor. EMB was performed in 21/26 patients with EF ≤30% (80.7%), in 7/13 patients with EF >30% and another risk factors (53.8%) and in 16/111 (14%) patients without risk factors. EMB led to the initiation of immunosuppressive therapy in 11/28 patients with risk factors (39.3%) and in none of the patients without risk factors (0/16, 0%, p=0.003)(figure 1). With respect to the subgroup of patients presenting with recurrent myocarditis (n=10), no specific therapy was performed. Conclusion Due to a high therapeutic yield for initiation of immunosuppressive therapy in non-infectious myocarditis, performing EMB should be considered in all high-risk patients. In patients without clinical risk factors including cases of recurrent or relapsing myocarditis no specific therapy was initiated.