Congenital long QT syndrome (LQTS) is an inherited heart rhythm disorder characterized by abnormal myocardial repolarization with potential ventricular arrhythmias and risks for sudden cardiac arrest. LQTS is linked to reduced cardiorespiratory fitness (CRF) and mental health vulnerability. We investigated associations between CRF and neurodevelopmental and mental health in pediatric LQTS.

This multicenter study enrolled children with congenital LQTS. CRF was assessed using the Ventilatory Anaerobic Threshold (VAT) and maximal oxygen uptake (VO2max). Neurodevelopment was assessed via standardized mean scores from the Wechsler Intelligence Scale for Children V, and the Behavior Rating Inventory of Executive Function, proxy-report. Anxiety and depression were measured via self-reports from the Revised Children's Manifest Anxiety Scale, and the Multiscore Depression Inventory for Children. Pearson correlations were computed independently between VAT and VO2max z-scores and neuropsychological indices, adjusted for IQ.

Twenty-three participants (mean age = 11 y ± 3.5 mo; 70% male) were enrolled. VAT correlated with working memory ( r = 0.44, p = 0.04) and processing speed ( r = 0.57, p = 0.01), whereas VO2max correlated with processing speed only ( r = 0.51, p = 0.02). None of the CRF measures were associated with executive functioning. Anxiety symptoms were related to lower VO2max (social concerns, r = −0.53, p = 0.01). Depression scores were related to both VAT and VO2max. Indeed, lower VAT and VO2max were associated with poorer scores on Sad Mood, Helplessness and Low Energy scales (all p < 0.05).

Reduced cardiorespiratory fitness was associated with specific neurocognitive outcomes. Reduced VO2max impacted anxiety and depression symptoms. Further research is needed to identify potential mechanisms underlying the relationship between CRF and neurodevelopment in LQTS.