Burchill et al. studied 106 adult Fontan patients and found elevated BNP (>100 pg/mL) in 33% of patients; elevated BNP was associated with older-style Fontan connections, older age, active arrhythmia, and reduced peak oxygen uptake on CPET (p < 0.05 for each) [30]. This evidence concerns the gene NPPB and Arrhythmia.