Quantification of ventricular stress in univentricular hearts during early childhood using age-independent zlog-NT-proBNP

Background: Children with univentricular hearts (UVH) undergo up to three palliative surgical procedures to achieve complete circulatory separation (Fontan circulation). As a marker of cardiac wall stress, NT-proBNP is a promising tool to assess systemic ventricular load in these patients. However, different reference intervals (RI) apply to each stage, as NT-proBNP is highly age-dependent. Methods: Children undergoing systemic-to-pulmonary (SP) shunt placement (stage 1), bidirectional cavopulmonary shunt (BCPS, stage 2) or total cavopulmonary connection (TCPC, stage 3) between 2011 and 2021 with NT-proBNP measurement within 7 days before surgery were included. Furthermore, outpatients after TCPC with NT-proBNP measurement were enrolled. Biomarker levels were evaluated using its age-adjusted z-score (“zlog-NT-proBNP”; age-independent RI, −1.96 to +1.96), allowing comparison between different stages and revealing changes in systemic ventricular load independent of the marked physiological decline in RI with age. Results: Overall, 289 children (227 before, 62 after TCPC) met the eligibility criteria. Median time between blood sampling and surgery (SP shunt/BCPS/TCPC) was 2 [1–3] days and 3.2 [2.0–4.5] years after TCPC. Age-adjusted zlog-NT-proBNP levels were 3.47 [2.79–3.93] in children with native UVH (before SP shunt), 3.10 [1.89–3.58] at stage 1 (before BCPS), 1.08 [0.51–1.88] at stage 2 (before TCPC), and 1.09 [0.72–1.75] at stage 3 (after TCPC/Fontan completion). Consequently, BCPS revealed the strongest decrease (median − 2.02 logarithmized standard deviations, p < 0.001). Conclusions: In children with UVH undergoing staged Fontan palliation, zlog-NT-proBNP is a highly promising tool for course assessment of systemic ventricular load, independent of the age-related decline in physiological NT-proBNP concentration.