Changes in AV node conduction curves following slow pathway modification

Dual AV node physiology often persists after successful slow pathway (SP) a blation, and the mechanism of tachycardia elimination is unresolved. Theref ore, AV node conduction curves were analysed following successful ablation (4 +/- 1 energy applications) in 85 consecutive patients (58 women, age 50 +/- 2 years) with typical AVNRT. Twenty-seven patients (32%) had complete e limination (group 2) whereas 58 (68%) patients had persistence (group 2) of dual AV node physiology. A significant increase in the AV node Wenckebach cycle length (WB-CL) was observed in both groups (310 +/- 9 to 351 +/- 25 m s in group 2, and 325 +/- 8 to 369 +/- 9 ms in group 2, P < 0.05). A decrea se in the fast pathway (FP) ERP (339 +/- 15 to 279 +/- 12 ms) and an increa se in the maximum FP AH interval (141 +/- 5 to 171 +/- 7) were observed onl y in group 2 (P < 0.05). In group 2, no change in the SP ERP (267 +/- 7 to 280 +/- 10 ms) was observed, and the change in the maximum SP-AH following ablation showed a significant inverse relation to the maximum SP-AH at base line in group 2. In conclusion, (1) an increase in the WB-CL is observed in dependent of the persis tence or elimination of dual physiology after succe ssful ablation; (2) when dual physiology is eliminated, significant changes in the FP ERP and the maximum FP-AH occur; (3) when dual physiology persis ts, FP physiology and the SP ERP remain unchanged, and a significant invers e relation between the change in the maximum SP-AH following ablation and t he maximum baseline SP-AH is observed.