Prognostic Parameters for a Severe Disease Course in Pediatric Patients with Suspected Myocarditis: Data from the Prospective Multicenter Registry “MYKKE”

Objectives: Myocarditis is one cause of severe heart failure in childhood. “MYKKE,” a multicenter prospective registry on pediatric patients with suspected myocarditis, aims with its ongoing enrollment to gain knowledge on incidence, diagnostic, therapy, and outcome.

Methods: Clinical symptoms, serologic results and echocardiographic parameters at admission where prospectively recorded in pediatric patients with suspected myocarditis from 22 sites. A severe course of the disease was defined as presenting at least one of the following events: death, survived, sudden cardiac death, mechanical circulatory support, decompensated heart failure, heart transplantation, catecholamine therapy, or malignant arrhythmia. Univariate logistic regression after multiple imputations was performed.

Result: A total of 415 patients were enrolled between September 2013 and June 2019 (35.4% female, median age/interquartile range 13.7/1.5–16.3 years) with an initial left ventricular ejection fraction (LVEF) of 53/35 to 62%. Forty-three percent of these patients experienced a severe disease course; 95% during first admission and the following risk factors have been identified: female gender (OR = 2.1, p = 0.001), younger age (OR = 0.8, p < 0.001), lower LVEF (OR = 0.9, p < 0.001) and an increase of the LV end-diastolic diameter Z-score (OR = 1.4, p < 0.001) raised the risk for a severe disease course. Notable, the chance to experience a severe disease course is 94% lower in patients with angina pectoris than in patients without angina pectoris (OR = 0.06, p < 0.001). Other prognostic variables were: elevated NT-pro-BNP (OR = 8.0), dyspnea (OR = 3.1), arrhythmia (OR = 2.9), and fatigue (OR = 2.6), p < 0.001, respectively. Patients with fever (OR = 0.6; p = 0.024) or infection (OR = 0.7, p = 0.081) within the last 6 weeks before symptom onset had a reduced risk, whereas elevated leucocytes lead to an increased risk (OR = 1.2, p < 0.001). Raised troponin levels had no significant impact (p = 0.914) and ST-elevation reduced the risk (OR = 0.4, p < 0.001).

Conclusion: Next to parameters of heart failure, age, and gender seem to be predictive to experience a severe disease course in pediatric patients with suspected myocarditis. Interestingly, signs of myocardial injury as angina pectoris and ST-elevation, as well as older age, may be leading to a milder clinical course, pointing toward two different responses in pediatric myocarditis.