Pulmonary Veins and Ligament of Marshall as Sources of Rapid Activations in a Canine Model of Sustained Atrial Fibrillation

Abstract

Background—In dogs, chronic rapid pacing may result in sustained atrial fibrillation (AF). However, activation patterns in pacing-induced sustained AF are unclear. Methods and Results—We induced sustained AF (>48 hours) in 6 dogs by rapid pacing for 139±84 days. We then performed computerized atrial epicardial mappings and recorded the activations in the ligament of Marshall (LOM) and the pulmonary veins (PVs). During AF, mean activation cycle length in the right atrial free wall (126±17 ms) was significantly longer than that in the left atrial free wall (96±5 ms, P=0.006). In addition, mean activation cycle length in the left atrial free wall was significantly longer than that in the LOM (84±5 ms, PP=0.001), and the left superior PV (85±7 ms, P=0.003). Similarly, the dominant frequency was highest in the LOM and the PVs (range 11.2 to 13.3 Hz), followed by the left and right atria (PPConclusions—In chronic pacing-induced sustained AF, the LOM and the PVs are the sources of rapid activations. The mechanism by which the left atrium activates faster and has more wave fronts than the right atrium may relate to the fact that the left atrium is closer to the sources of rapid activations.