Are electrophysiological changes induced by longer lasting atrial fibrillation reversible? Observations using the atrial defibrillator

Background-Studies in animal hearts have shown shortening of the atrial eff ective refractory period (AERP) and loss of the relation between the AERP a nd heart rate after prolonged periods of atrial fibrillation (AF), The purp oses of this study were (1) to evaluate atrial electrophysiology after a lo ng period of sinus rhythm in patients who had longer lasting recurrent AF t hat was successfully treated with the Metrix Atrioverter and (2) to analyze the effect of prompt cardioversion on subsequent AF episodes and the durat ion of sinus rhythm. Methods and Results-Four patients with recurrent AF (duration, 3 to 21 year s; mean+/-SD, 13+/-7.6 years) were studied after the implantation of an Atr ioverter. The Atrioverter stores and analyzes 3 minutes of cardiac rhythm e very hour. Before implantation, AERP was measured. During a mean follow-up of 14 months, 52 spontaneous (39 treated and 18 nontreated) AF episodes occ urred while the patients were on antiarrhythmic drugs. All patients were el ectrophysiologically studied after they had been in sinus rhythm for at lea st 1000 hours (range, 1052 to 2675 hours). Before Atrioverter implantation, AF was induced by 1 atrial premature beat in 3 patients and not induced in the remaining patient, After a long period in sinus rhythm (>1000 hours), AF could be induced in the same 3 patients in the same way as before implan tation. In the patient in whom no AF was induced, right AERP values measure d using the single extrastimulus technique at 3 pacing cycle lengths (600, 500, and 430 ms) were similar to those before implantation. Conclusions-AF was still inducible by a single atrial premature beat after long episodes of sinus rhythm in 3 of 4 patients with previously longer las ting AF. In the patient in whom no AF was induced, AERP behaved like it did before implantation. In these patients with longer lasting recurrent AF, n o return to "normal" atrial electrophysiology could be demonstrated.