Age related changes in dual AV nodal physiology

Dual atrioventricular nodal (DA VN) physiology has been reported in up to 6 3% of pediatric patients with anatomically normal hearts, yet atrioventricu lar nodal reentrant tachycardia (AVNRT) accounts for only 13%-16% of suprav enticular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investi gated the age related electrophysiological responses to programmed atrial a nd Ventricular stimulation in 14 pediatric patients who underwent intracard iac electrophysiological study prior to radiofrequency catheter ablation fo r AVNRT and who exhibited DAVN physiology. Single atrial and ventricular ex trastimuli were placed following drive trains with cycle lengths of 400-700 ms and 350-500 ms, respectively. Six children (mean age 8.2 years, range 5 .2-11.5 years) were compared to eight adolescents (mean age 16.6 years, ran ge 13.3-20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0 .03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio-Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (med ian 350 vs 290ms, P = 0.03). There was a strong trend for the AH measured a t the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongl y correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, p = 0.7). There was no significant difference in the retrograde V A conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli i n pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNR T in adolescents compared to children.