Occurrence and Severity of Arrhythmias in Children and Adolescents with Proven Myocarditis—Data from Prospective, Multicenter Registry “MYKKE”

Background: The spectrum of myocarditis ranges from asymptomatic courses to severe heart failure. Cardiac arrhythmias are another feared complication. The aim of this study is to evaluate initial arrhythmias and their occurrence in the long-term course in pediatric patients with myocarditis to define certain risks.

Methods: Enrolled patients in the prospective, multicenter registry “MYKKE” with proven myocarditis in endomyocardial biopsy (EMB) and/or CMR were assessed for the occurrence of bradycardic and tachycardic arrhythmias (TA) during initial admission and follow-up (FU). TA included significant supraventricular (SVES) and ventricular extrasystolia (VES), bigeminus, supraventricular (SVT) and ventricular tachycardia (VT) according to current guidelines. Major cardiac events (MACE) were defined as ECMO/VAD, heart transplant and/or death.

Results: Twenty-five centers enrolled 781 patients. 466 presented with proven myocarditis (median (IQR) age of 15.1 (8.4–16.5) years; 70% male). Within this cohort, 13 were administered with a 3rd degree atrioventricular block. Eighty-eight (19%) children (15.5 (11.2–16.4) years; 74% male) presented with following TA: 9% SVES, 55% VES, 30% bigeminus, 22% SVT, 57% non-sustained VT and 13% sustained VT. One had an ablated AVRNT in history. Symptoms were exercise intolerance (72%), angina pectoris (42%), dyspnea (42%), syncope (21%), feeding intolerance (18%), and sudden cardiac death (10%). TA was not age (p = 0.549) or sex (p = 0.310) dependent compared with patients without TA. However, TA patients had a significant lower left ventricular ejection fraction (LVEF; 45% vs. 55%; p = 0.008). MACE occurred more significantly in the TA group (31%; p < 0.001). Myocardial virus detection in EMB (p = 0.014) and late gadolinium enhancement in CMR was less frequently presented in TA (64% vs. 78%; p = 0.024). TA patients received in 83% a β-blocker, 36% received an additional antiarrhythmic medication. In 17 (19%) TA patients electrophysiological studies with seven ablations were performed. Within a FU of 1.1 (0.5–2.6) year, 50% of 385 patients received a Holter; 19% (n = 38) presented with TA, mostly VES and nsVTs; 29% (11/38) were patients with new TA.

Conclusion: Cardiac arrhythmias occur frequently in pediatric myocarditis, depending on LVEF and irrespective of age and sex. TA requiring therapy, occur also frequently at FU. Consequently, rhythm monitoring initially and during FU are important and recommended for all patients with myocarditis.

Publication History

Article published online:
13 February 2024