Objectives: We determined whether acetylcholine (Ach) application to the pulmonary vein (PV) wall could induce AF and clarified its mechanisms, and determined whether circumferential PV radiofrequency ablation (CPVA) could prevent Ach-induced AF in canine hearts.
Methods: Thirty seven beagle dogs were used for the study. Ach was injected into the subadventitial layer of the left superior PV (LSPV), at different distance from the LSPV-left atrium junction (LSPV-LA-J) to locate AF initiation. When AF was not induced by Ach alone, programmed electrical stimulation (S1-S2 method) was added to elicit AF. Atropine was injected at the same site of Ach injection to determine whether muscarine-receptor blockade suppressed AF, and CPVA at the LSPV-LA-J was performed using a newly devised basket electrode-catheter.
Results: AF was reproducibly induced by Ach injection in 19 of the 26 dogs (73%). S1-S2 method after Ach initiated AF in 5 of the remaining 7 dogs. Ach into the subadventitial layer of the LSPV, especially the distal portion, could elicit AF, which was preceded by pause (sinus arrest) ≥ 2.0 sec (37%) (pause-AF group), sinus bradycardia (32%) (brady-AF group) and sinus tachycardia (32%) (tachy-AF group). The time from Ach injection to AF initiation and AF duration were not significantly different between pause-AF, brady-AF and tachy-AF groups. AF was not initiated by injecting Ach after atropine pretreatment. To eliminate AF, 1-6 (average 4.1 ﾂｱ 1.2) CPVAs at the LSPV-LA-J were required.
Conclusions: Our observations suggest that local Ach application can initiate AF in PVs, preceded by a variety of modes such as pause, bradycardia or tachycardia, and an increase in vagal tone at the LSPV plays a critical role in eliciting AF in structurally normal heart.