Multisystem inflammatory syndrome in children (MIS-C) is characterized by persistent fever and gastrointestinal, mucocutaneous, cardiac, respiratory, and/or neurological system involvement due to hyperinflammation that often occurs 2–6 weeks after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Cardiac involvement is seen in 67 %–80 % of patients with MIS-C [1]. Many acute cardiac outcomes have been reported in patients with MIS-C, including cardiac enzyme abnormalities; electrocardiogram abnormalities; decreased systolic function; coronary artery abnormalities; mitral, tricuspid, and aortic valve insufficiencies; pericardial effusion; diastolic dysfunction; and atypical cardiac strain [2]. Electrocardiographic abnormalities observed during the MIS-C course include atrioventricular blocks, bradycardia, tachyarrhythmias, ST segment or T wave changes, and prolonged QTc intervals [3]. Echocardiographic abnormalities observed in patients with MIS-C include decreased systolic function, coronary artery abnormalities, valvular insufficiency, and pericardial effusion [2].

Recent clinical studies in children and adults have shown that P wave dispersion, QT interval, QT interval dispersion, and heart-rate-corrected QT dispersion obtained by electrocardiography are associated with myocardial susceptibility to arrhythmias [4,5]. P wave dispersion is characterized by heterogeneity in the conduction of intra-atrial/interatrial sinus impulses, and its prolongation is a risk indicator for atrial arrhythmia. Numerous studies have evaluated P wave dispersion in patients with acute rheumatic fever, hypertension, paroxysmal atrial fibrillation, mitral stenosis, aortic stenosis, and spontaneous angina pectoris [[6], [7], [8], [9], [10], [11]]. QT interval dispersion has been associated with increased cardiovascular mortality and morbidity in patients with peripheral vascular disease, ischaemic heart disease, dilated and hypertrophic cardiomyopathies, hypertension, and renal disease [12,13]. According to these studies, increased QT interval and corrected QT interval dispersion indicate heterogeneous myocardial repolarisation and myocardial electrical imbalance and, thus, increased risk of ventricular arrhythmias [4,14].

To our knowledge, no studies have examined the relationship between P wave and QT interval dispersion in patients with MIS-C. Therefore, this study compared P wave, QT interval, and corrected QT interval dispersion and echocardiographic measurements between patients with MIS-C at presentation and after treatment and ostensibly healthy controls.