Objectives: The purpose of the present study was to evaluate the electrophysiologic properties within the pulmonary vein (PV) and at the PV-left atrial (LA) junction.
Background: It has been recognized that atrial fibrillation (AF) can originate from PVs. However, the electrophysiologic properties of the PV have not been well characterized.
Methods: Thirty-two bipolar electrograms were recorded simultaneously from a basket catheter placed in 81 PVs of 48 patients with paroxysmal AF. The programmed stimulation was performed in the distal PV and PV-LA junction. Activation maps of PVs were analyzed from episodes of spontaneous onset of AF and initiation of induced AF by a single extrastimulus.
Results: The effective refractory period (ERP) of the distal PV was significantly shorter than that of the PV-LA junction (177 +/- 43 vs. 222 +/- 30 ms, p < 0.0001). The conduction delay from the distal PV to the PV-LA junction was significantly longer than that from the PV-LA junction to distal PV (73 +/- 40 vs. 32 +/- 17 ms, p < 0.0001). During initiation of AF, a short coupled extrastimulus or rapid, repetitive focal activities originating from the PV formed a PV-LA reciprocating re-entrant circuit involving exit and entrance breakthrough points at the PV-LA junction. Also, an unstable re-entrant circuit within the PV was observed.
Conclusions: The presence of ERP heterogeneity and anisotropic conduction properties within the PV and at the PV-LA junction may be crucial to promote re-entry formation and thus might play an important role as a substrate for the maintenance of AF.