Processing Speed Partially Mediates Executive Function Impairments in Adolescents with Congenital Heart Disease: Results from a Prospective Cohort Study.

Objective: To assess processing speed, fine motor function, attention, and executive function (EF) impairments in adolescents with complex congenital heart disease (CHD) who underwent open-heart surgery during infancy.

Study Design: We administered a comprehensive neuropsychological test battery evaluating 5 EF domains: working memory, inhibition, cognitive flexibility, fluency, and planning and primary neurodevelopmental processes (PNPs): processing speed, fine motor function, and attention. The sample included 100 adolescents with complex CHD from a previous University Children's Hospital Zurich study, with 104 healthy controls for comparison. We generated scores for each EF domain and computed an EF summary score. Group comparisons and associations were analyzed with multiple regressions accounting for parental education. Mediation analysis explored how PNPs mediate the effect between a CHD diagnosis and EF.

Results: In adolescents with complex CHD, all EF domains and the EF summary score were impaired (β = 0.20 to 0.37, all P < .05). Furthermore, they exhibited slower processing speed (β = 0.27, P < .01) than healthy controls, with no differences in attention (β = -0.07, P = .34) and fine motor function (β = 0.08, P = .34). Processing speed showed a strong association with the EF summary score (β = 0.60, P < .001) and partially mediated the relationship between CHD diagnosis and the EF summary score (β = 0.37, 95% CI [0.24, 0.50], P < .001).

Conclusion: Adolescents with complex CHD show difficulties in EFs and processing speed. Notably, processing speed is strongly associated with EFs and partly accounts for EFs disparities between patients and healthy controls. Early detection and interventions for processing speed difficulties may improve EF outcomes in these patients.