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

Background: In the past decades, cardiovascular magnetic resonance (CMR) was established as a non-invasive tool supporting the diagnosis of myocarditis and there is often reluctance in performing EMB due to potentially severe complications. We sought to identify patient subgroups that could still benefit from EMB in the CMR era.

Methods: Data of patients presenting with myocarditis between 01/2016 and 06/2023 were analysed according to patient risks. Prespecified risk factors were (i) left ventricular ejection fraction (LVEF) ≤ 30%; (ii) severe arrhythmias; or (iii) pre-existing autoimmune disease. Furthermore, the subgroup of recurrent myocarditis cases was analysed separately.

Results: A total of 137 patients (35.5 ± 14.8 years, 80.3% male) were included. 26/137 patients had a documented LVEF ≤ 30%, 13/137 a LVEF > 30% with at least one other risk factor and 98/137 a LVEF > 30% without risk factors. EMB was performed in 21/26 patients with LVEF ≤ 30% (80.8%), in 7/13 patients with LVEF > 30% and risk factors (53.8%) and in 16/98 (16%) 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). With respect to the subgroup of patients presenting with recurrent myocarditis (n = 10), no specific therapy was initiated.

Conclusions: 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.