Clinical case: Myocarditis in an adolescent with post-COVID syndrome

Myocarditis in children is a diagnostically challenging disease with a variable course ranging from subclinical forms to severe heart failure and sudden cardiac death. Of particular interest are myocardial lesions in adolescents after COVID-19 infection, the mechanisms of which are not fully understood. The aim of this clinical observation is to demonstrate the current possibilities of comprehensive diagnostics of subacute myocarditis in an adolescent with post-COVID syndrome. We present a case of a 15-year-old patient who, 10 months after contact with his mother ill with COVID-19, developed severe asthenia, weight loss, bradycardia, and ECG changes. The key diagnostic method for myocarditis was cardiac magnetic resonance imaging (MRI) with gadolinium contrast, which revealed myocardial edema, areas of necrosis and fibrosis. This case illustrates that in post-infectious myocarditis with bradycardia and sick sinus syndrome, normal troponin levels do not rule out the diagnosis. Cardiac MRI is the method of choice for verifying inflammatory and fibrotic changes. TREC/KREC analysis is promising for assessing immune deficiency, which predisposes to the development and/or chronification of myocarditis in the post-COVID period.