Abstract 1256: Are Intact Pulmonary Veins Necessary for Vagal Atrial Fibrillation?
Background: Pulmonary vein (PV) encircling ablation is clinically effective in vagal AF, but the specific role of PVs (vs peri-PV structures) is unclear. This study was designed to assess the role of PVs per se in vagal AF with complementary in vivo and in vitro dog models.
Methods: Left atrial (LA) action potential duration (APD) and AF duration were recorded in vitro with fine-tipped standard microelectrodes in coronary-perfused LA-PV preparations of 5 dogs before and during carbachol (CBL, 500 nM) infusion, and measurements repeated after excision of all PVs at their ostia. Atrial effective refractory period (AERP) and AF duration were measured in vivo with and without vagal stimulation before and after circumferential radiofrequency PV ablation in 6 open-chest morphine/ chloralose anesthetized dogs.
Results: In vitro, CBL decreased APD to 90% repolarization (APD90) at cycle length (CL) 500 ms from 210±25 to 39±7ms (**p<0.01) before, and from 196±23 to 44±8 ms (*p<0.05) after, PV excision (†P=NS for cholinergic response pre- vs post-ablation). PV excision had no effect on AF duration: AF was sustained continuously with CBL both before and after PV excision. In vivo AERP (at CL 300 ms) decreased with vagal stimulation from 116±16 to 78±29** ms before and from 132±19 to 80±25** ms after ablation†. Pre-ablation, PV tachycardias (mean CL 47±31 ms) faster than LA appendage activity (CL 85±16 ms) occurred during vagal AF in all dogs, with the fastest activity in the right superior (RS) PV in all. Ablation disconnected all PVs and eliminated PV tachycardias during vagal AF. Nevertheless, sustained AF could be induced in the presence of same-intensity vagal stimulation for all dogs both before and after ablation. Ostial tachycardias were recorded proximal to the ablation line both pre- and post-ablation, but the CL was slowed by ablation (eg, in RS PV ostium from 49±12 pre- to 72±22* ms post-ablation).
Conclusions: PV excision does not suppress cholinergic AF in vitro, nor does PV disconnection prevent sustained vagal AF in vivo. Thus, the presence of intact PVs is not needed for maintenance of vagal AF, suggesting that other factors (like ablation of ganglia, the PV-LA junction or primary PV foci) may account for the clinical effectiveness of PV isolation procedures in vagal AF.