Normal Sinus Rhythm–Sinus Bradycardia is Common in Young Children Post-extracardiac Fontan

We hypothesized that normal sinus rhythm–sinus bradycardia is common in young children following extracardiac Fontan. After excluding patients with sinus pauses, junctional rhythm, tachy–brady syndrome, frequent ectopics, or ectopic atrial rhythm, we found an ambulatory 24-h Holter monitor average heart rate of 78 ± 12 beats per minute (bpm) in 33 post-extracardiac Fontan children with a median age of 6 years (5–10). A 24-h average heart rate of 78 ± 12 bpm is statistically significantly lower than a 24-h average heart rate value of 90 ± 10 bpm derived from a similarly aged control population (p < 0.01). We conclude that after excluding those with significant arrhythmias, normal sinus rhythm–sinus bradycardia is common in children post-extracardiac Fontan.