Abstract 1084: Activation Exits the Pulmonary Vein Area via Preferential Conduction Pathways
Background: The region of the pulmonary veins (PV) is believed to play a critical role in the genesis and the maintenance of atrial fibrillation. The pattern of conduction from the PV area to activate the atria is not well understood. We tested the hypothesis that exit of activation during rapid pacing from the PV area would occur via preferential pathways.
Methods: In 13 canines with sterile pericarditis, rapid atrial pacing at cycle lengths of 400, 300, 200, and/or 150 ms was performed from plunge electrodes placed at sites between either the 2 right PVs (2 dogs), 2 inferior PVs (7 dogs), or 2 left PVs (6 dogs). Simultaneously recorded epicardial high density maps of both atria (510 electrodes) and PV area (20 electrode catheter) were analyzed.
Results: There was no evidence of activation spreading radially from any pacing site. Pacing from between the 2 right or 2 inferior PVs resulted in a wave front entering the left atrial free wall (LAFW) at a site distant from the pacing site, namely between the inferior vena cava and the right inferior PV (8/9 episodes) or between the right inferior and the left inferior PVs (1/9 episodes). Pacing from between the 2 left PVs resulted in a wave front entering the LAFW between the 2 left PVs (3/6 episodes), between the right and left inferior PVs (2/6 episodes), or between the inferior vena cava and the right inferior PV (1/7 episodes). Bachmann’s bundle was activated via an endocardial breakthrough at the septal junction between the superior vena cava and the right superior PV, with activation then traveling to both the left and right appendages in 13/15 episodes irrespective of the pacing site. This activation pattern resulted in collision of the LAFW wave front and the Bachmann’s bundle wave front in the area lateral to the PVs. In the remaining 2 episodes, Bachmann’s bundle was activated from between the 2 superior PVs when paced from between the 2 left PVs.
Conclusions: Pacing studies indicate that activation exits the PV area via preferential conduction pathways. This has important implications for understanding the genesis of atrial fibrillation and the efficacy of lesions used for ablation to cure it.