High resolution mapping of the pulmonary vein and the vein of Marshall during induced atrial fibrillation and atrial tachycardia in a canine model of pacing-induced congestive heart failure.

OBJECTIVES: The study examined the activations in the pulmonary veins (PVs) and the vein of Marshall (VOM) during atrial fibrillation (AF) in dogs with congestive heart failure (CHF).
BACKGROUND: The patterns of activation within the PVs and the VOM during AF in CHF are unclear.
METHODS: We induced CHF in nine dogs by rapid ventricular pacing. The patterns of activation during induced AF were studied one week after ceasing ventricular pacing.
RESULTS: The duration of induced AF averaged 80.7 +/- 177.3 s. The termination of low-amplitude fractionated activity in the PVs preceded the termination of AF in 25 of 29 episodes. High-density mapping (1-mm resolution) showed that the PV was activated by a focal wave front independent of left atrial (LA) activation in 22 AF episodes. Frequent intra-PV conduction blocks and multiple wave fronts in the PVs were recorded during 10 AF episodes. Focal activations were observed within the VOM in 4 of 12 episodes of AF. Three atrial tachycardia (AT) episodes originated from a focus within a PV. Histological studies showed extensive fibrosis in the PVs and in the atria. The PVs in five normal dogs did not have focal or fractionated activity during induced AF.
CONCLUSIONS: Atrial fibrillation in canine CHF is associated with independent focal activations in the PVs and the VOM, and with complex wave fronts within the PVs. The PVs may also serve as the origin of AT. These findings suggest that electrical and anatomical remodeling of the PVs and the VOM are important in the maintenance of AF and AT in dogs with CHF.