Early Recurrences of Atrial Fibrillation After Electrical Cardioversion: Result of Fibrillation-Induced Electrical Remodeling of the Atria?

Objectives. We sought to investigate whether, in humans, the timing and incidence of relapse of atrial fibrillation (AF) during the first month after cardioversion indicates the presence of electrical remodeling and whether this could be influenced by prevention of intracellular calcium overload during AF. Background. Animal experiments have shown that AF induces shortening of the atrial refractory period, resulting in an increased vulnerability for reinduction of AF. This electrical remodeling was completely reversible within 1 week after cardioversion of AF and was presumably related to intracellular calcium overload. Methods. Using transtelephonic monitoring in 61 patients cardioverted for chronic AF, we evaluated the daily incidence of recurrence of AF and determined, by Cox regression analysis, the influence of patient characteristics and medication on relapse of AF. Results. During 1 month of follow-up, 35 patients (57%) had relapse of AF, with peak incidence during the first 5 days after cardioversion. Furthermore, in patients with recurrence of AF, there was positive correlation between the duration of the shortest coupling interval of the premature atrial beats after cardioversion and the timing of the recurrence of AF (p = 0.0013). Multivariate analysis revealed that the use of intracellular calcium-lowering drugs during AF was the only significant variable related to maintenance of sinus rhythm after cardioversion (p = 0.03). Conclusions. The daily distribution of recurrences of AF suggests temporary vulnerable electrophysiologic state of the atria. Use of intracellular calcium-lowering medications during AF appeared to reduce recurrences, possibly due to reduction of electrical remodeling during AF.