Impact of Endomyocardial Biopsy on Treatment and Outcome in Pediatric Myocarditis: Results from the German Multicenter Registry for Pediatric Myocarditis “MYKKE”

Objective: Endomyocardial biopsy (EMB) in pediatric patients is divergently discussed, but it might identify the underlying etiology of severe heart failure. EMB might trigger therapeutic interventions and have a prognostic value. As there is no standard, the aim of this study was to analyze the impact of EMB in pediatric patients with suspected myocarditis.

Methods: EMB results from patients enrolled between September 2013 and August 2018 in the German prospective multicenter registry “MYKKE” were analyzed.

Results: In 56% (200/357) of patients an EMB was performed. EMB results from 182 patients were available for analysis. Median age was 13.0 (1.2–16.3) years. Time between symptom onset and EMB was 11.0 (4.0–26.5) days, between first admission and EMB 3.0 (1.0–8.8) days. Ninety per cent were taken from right ventricle (RV), 5% from left ventricle (LV), and 5% from LV/RV. In 137 (75%) patients, a myocarditis was reported: acute myocarditis (18%), subacute/chronic myocarditis (41%), status postmyocarditis (10%), borderline myocarditis (4%), and hypersensitivity myocarditis (1%). In 7%, no relevant inflammation was documented, 6% had a DCM, 2% LVNC, 2% HCM; 9% had other diagnosis. In 42% (77/167), cardiotropic viruses in the myocardium could be detected (57% PBV19; 18% HHV6; 13% PVB19/HHV6; 4% CMV; 3% enterovirus; 1% EBV, HHV6/7), with mostly low viral loads (n = 56). Time between admission (p = 0.149) and symptom onset (p = 0.096) had no significant impact on virus detection or diagnosis of myocarditis. Immunoglobins were not administered more frequently after virus detection (p = 0.525) or diagnosis myocarditis (p = 0.293). Eight patients (4%) received immunosuppressive and 22 (12%) a virostatic therapy. Virus positivity or the diagnosis of myocarditis had no significant impact on need for HTX, MCS, or death. Age groups or the normalization of ejection fraction at follow-up was neither correlated with myocardial virus detection nor inflammation.

Conclusion: The rate of myocarditis and viral DNA detection in pediatric EMB for suspected myocarditis is unexpected high. Although a large proportion of subacute or chronic cases and low viral loads are detected, it does not trigger a specific therapy or influence outcome in this cohort. Timing may play a critical role for viral detection and therapeutic interventions. For that purpose, further investigations and standardized protocols are necessary to allow comparing EMB findings and advancing the understanding of myocarditis.

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