Electrophysiologic Changes in Arrhythmogenic Substrate Following the Maze Procedure in Patients With Lone and Paroxysmal Atrial Fibrillation

Although the Maze procedure is highly successful in restoring sinus rhythm in patients with atrial fibrillation (AF), the electrophysiologic changes that occur after the Maze procedure and its mechanism of action are still unclear. The aims of the present study were to examine the electrophysiologic changes that occur in the arrhythmogenic substrate after the Maze procedure and to evaluate the mechanism by which it prevents lone and paroxysmal AF. The modified Maze procedure was performed in 6 patients (6 men, mean age 47 +/- 7 years) with lone and paroxysmal AF. Electrophysiologic studies were performed before and 35 +/- 8 days after the Maze procedure. Atrial mapping during sinus rhythm revealed that atrial activation propagated smoothly in a concentric circle from the sinus node to other regions in the right atrium and into the coronary sinus before the Maze procedure. Following the Maze procedure, atrial activation propagated selectively through routes produced by incisions or cryoablations in all 6 patients. In addition, double and triple potentials were recorded in regions where conduction blocks were created by the Maze procedure. Neither sinus node function nor AV conduction was changed following the Maze procedure. The Maze procedure did not affect the atrial effective refractory period or the zone of fragmented atrial activity, although the conduction delay zone was increased significantly (p < 0.05). AF was inducible in all 6 patients before the Maze procedure, whereas it was not inducible in any patients after the Maze procedure. The Maze procedure is effective in preventing AF without affecting sinus node function and AV conduction. Intra-atrial conduction block produced by incisions or cryoablations contributes to the prevention of AF.