Background—Atrial electrical remodeling may be important for the initiation and perpetuation of atrial arrhythmias. Whether paroxysmal atrial flutter (AFL) and chronic AFL cause electrical remodeling of the atria has not been conclusively determined.

Methods and Results—Before radiofrequency ablation of paroxysmal AFL, 15 patients in sinus rhythm were evaluated under autonomic blockade. Lateral right atrial (LRA) effective refractory periods (ERPs) at 600 and 450 ms were measured before and at 1-minute intervals for 10 minutes after spontaneous or pace termination of a 5- to 10-minute period of induced AFL. In 10 patients with chronic AFL, LRA, septal, and coronary sinus (CS) ERPs and corrected sinus node recovery times (cSNRTs) at 600 and 450 ms were measured under autonomic blockade 15 minutes, 30 minutes, and 3 weeks after termination of chronic AFL by ablation. In the paroxysmal AFL group, LRA ERPs decreased by 18% at 600 ms and 12% at 450 ms (P<0.01) after induced AFL and recovered to baseline over ≈5 minutes. Atrial fibrillation developed during AFL in 3 patients and during ERP testing in 3 patients when refractoriness was at its nadir. In the chronic AFL group, LRA, septal, and CS ERPs at 3 weeks were significantly greater than at 15 and 30 minutes after termination of chronic AFL at both cycle lengths (P<0.01). Three weeks after ablation, cSNRT decreased 35% at 600 ms (P<0.05) and decreased 44% at 450 ms (P<0.05). Both ERPs and cSNRTs measured 15 and 30 minutes after ablation of chronic AFL were not significantly different.

Conclusions—Both paroxysmal AFL and chronic AFL cause reversible electrical remodeling of the atria but demonstrate different time courses of recovery.