Patterns of activation in human atrial fibrillation.

The electrophysiological properties within the pulmonary vein (PV) and PV-left atrial (LA) junction were evaluated using a basket catheter in patients with paroxysmal atrial fibrillation. The effective refractory period of the distal PV was significantly shorter than that of the PV-LA junction. The conduction delay from the distal to proximal PV was significantly longer than that from the proximal to distal PV. During initiation of AF, a reentry involving exit and entrance breakthrough points at the PV-LA junction was observed. The presence of anisotropic conduction properties at the PV-LA junction may be critical to promote reentry formation.