Influence of age on atrioventricular conduction intervals in children with and without atrial septal defect.

His bundle electrograms were recorded in 42 patients with secundum atrial septal defects (ASD) and in 50 controls, aged 1 month to 16 years, in normal sinus rhythm and with normal PR intervals. Intervals PA (P less than 0.01) and PR (P less than 0.02) were found to be significantly prolonged in ASD patients. Analyzing the results according to age, a significant increase for intervals AH (P less than 0.05), HV (P less than 0.001) and PR (P less than 0.001) was noted in the oldest ASD children as compared to the younger ASD children, whereas in controls only the PR interval was found to be significantly prolonged (P less than 0.05) in the oldest subgroup. Under the age of three years, atrioventricular conduction intervals were not significantly different whether or not an ASD was present. However, in older children with ASD as compared to controls, a significant increase was noted for interval PA (P less than 0.03) in children four to eight years old and for intervals HV (P less than 0.01) and PR (P less than 0.001) in children 9 to 16 years old. ASD patients showed a more significant correlation with age for interval PR with a significantly steeper slope of the regression line. Results show the impact of ASD on AV conduction to be age-related, with involvement not only of the PA interval but also of the HV interval.