NT-proBNP Levels Following IVIG Treatment of Multisystem Inflammatory Syndrome in Children.

Background And Objectives: N-terminal of probrain natriuretic peptide (NT-proBNP) and C-reactive protein (CRP) levels are often elevated in multisystem inflammatory syndrome in children (MIS-C) secondary to inflammation, myocardial dysfunction, or increased wall tension. Intravenous immunoglobulin (IVIG), accepted treatment of MIS-C, may transiently increase myocardial tension and contribute to an increase in NT-proBNP. We sought to study the association between pre- and post-IVIG levels of NT-proBNP and CRP and their clinical significance.

Methods: This single-center, retrospective, cohort study included consecutive children, aged ≤21 years, with diagnosis of MIS-C who received IVIG from April 2020 to October 2021. Data collection included clinical characteristics, laboratory tests, management, and outcomes. Study cohort consisted of patients who received IVIG and had NT-proBNP levels available pre- and post-IVIG.

Results: Among 35 patients with MIS-C, 30 met inclusion criteria. Twenty-four, 80%, showed elevation in NT-proBNP post-IVIG. The median NT-proBNP level pre-IVIG was 1921 pg/mL (interquartile range 548-3956), significantly lower than the post-IVIG median of 3756 pg/mL (interquartile range 1342-7634)) (P = .0010). The median pre-IVIG CRP level was significantly higher than the post-IVIG level (12 mg/dL vs 8 mg/dL, P = .0006). All but 1 recovered before discharge, and none had signs of worsening cardiac function post-IVIG. In those who recovered, NT-proBNP had normalized by discharge or 1-week follow-up.

Conclusions: Our study shows that NT-proBNP levels often transiently increase immediately after IVIG therapy without signs of worsening myocardial function. These values should be interpreted in the context of CRP levels and clinical recovery.