Atrioventricular Conduction Abnormalities in Multisystem Inflammatory Syndrome in Children.

Cardiac manifestations in multisystem inflammatory syndrome in children (MIS-C) can include coronary artery aneurysms, left ventricular systolic dysfunction, and electrocardiographic disturbances. We report the clinical course of three children with MIS-C while focusing on the unique considerations for managing atrioventricular conduction abnormalities. All initially had normal electrocardiograms but developed bradycardia followed by either PR prolongation or QTc elongation. Two had mild left ventricular ejection fraction dysfunction prior to developing third-degree heart block and/or a junctional escape rhythm; one had moderate left ventricular systolic dysfunction that normalized before developing a prolonged QTc. On average, our patients presented to the hospital 4 days after onset of illness. Common presenting symptoms included fevers, abdominal pain, nausea, and vomiting. Inflammatory and coagulation factors were their highest early on, and troponin peaked the highest within the first two days; meanwhile, peak brain-natriuretic peptide occurred at hospital days 3-4. The patient's lowest left ventricular ejection fraction occurred at days 5-6 of illness. Initial electrocardiograms were benign with PR intervals below 200 milliseconds (ms); however, collectively the length of time from initial symptom presentation till when electrocardiographic abnormalities began was approximately days 8-9. When comparing the timing of electrocardiogram changes with trends in c-reactive protein and brain-natriuretic peptide, it appeared that the PR and QTc elongation patterns occurred after the initial hyperinflammatory response. This goes in line with the proposed mechanism that such conduction abnormalities occur secondary to inflammation and edema of the conduction tissue as part of a widespread global myocardial injury process. Based on this syndrome being a hyperinflammatory response likely affecting conduction tissue, our group was treated with different regimens of intravenous immunoglobulin, steroids, anakinra, and/or tocilizumab. These medications were successful in treating third-degree heart block, prolonged QTc, and a junctional ectopic rhythm.