APOE and Atypical behavior: 1998). We previously identified and validated an association of APOE genotype with early neurodevelopmental outcomes after cardiac surgery in neonates and infants with CHD (Gaynor et al. 2003, 2009, 2014). The APOE ε2 allele (described in Materials and Methods) was associated with worse performance at 12–14 months of age after surgery and with an increased risk of behavior problems at 4 years of age, while the APOE ε4 allele was associated with better outcomes.