B-type natriuretic peptide at the early stage of univentricular circulation reflects inadequate adaptation to volume overload

Background: Recent studies showed that children with univentricular heart have elevated plasma B-type natriuretic peptide (BNP) levels prior to bidirectional cavopulmonary anastomosis (BDCPA). However, it remains to be established whether BNP levels reflect the degree of hemodynamic overload and relate to long-term outcome in univentricular circulation. Methods: Fifty one consecutive children with functionally univentricular heart prior to BDCPA were studied. All patients underwent cardiac catheterization and BNP measurement. Ventricular end-systolic wall stress (ESWS) and end-diastolic wall stress (EDWS) were calculated from cardiac catheterization data. Results: Median age was 1.1 years and 34% were female. Median BNP concentration was 90.4 pg/ml. Patients with high BNP (≥ 100 pg/ml) had higher pulmonary to systemic flow ratio (p = 0.014), a greater end-diastolic volume (p = 0.009), more severe atrioventricular valve regurgitation (p = 0.02) and lower ventricular mass to end-diastolic volume ratio (p = 0.006). BNP levels strongly related to EDWS (r = 0.75, p < 0.0001) and ESWS (r = 0.63, p < 0.0001). During median follow-up period of 3.2 years, 15 patients died and one underwent heart transplantation for refractory heart failure. On multivariate Cox regression analysis, high BNP concentration was an independent predictor of death or transplantation (HR 3.05, CI: 1.06-8.83, p = 0.04). Conclusions: High BNP concentration at the first palliative stage towards Fontan circulation reflects high wall stress due to high volume load and insufficient ventricular hypertrophy. Moreover, high BNP levels at this stage were independently related to long-term outcome. BNP may be used as a guide to identify patients with high workload due to inadequate adaptation to hemodynamic load, who are at high risk.