Arrhythmic complications after electrical cardioversion of acute atrial fibrillation: the FinCV study.

Aims: To determine the incidence and risk factors of arrhythmic complications after electrical cardioversion of acute atrial fibrillation (AF).

Methods And Results: Our retrospective multicentre study collected data from 7660 cardioversions of acute (<48 h) AF in 3143 consecutive patients. Immediate arrhythmic complications were evaluated after 6906 (90.2%) electrical cardioversions performed in 2868 patients. We also assessed the predictors of arrhythmic complications and whether post-cardioversion bradycardia or asystole led to later a permanent pacemaker implantation. Altogether, 63 (0.9%) electrical cardioversions resulted in bradyarrhythmia in 54 patients. Asystole (>5 s) occurred immediately after 51 cardioversions leading to a short resuscitation in seven cases and two patients needed extrinsic pacing after the cardioversion. In nine cases, asystole was followed by bradycardia. Bradycardic ventricular rate (<40 b.p.m.) alone was seen after 12 procedures. No ventricular arrhythmias needing intervention were detected. Old age [odds ratio (OR) 1.1; 95% confidence interval (CI) 1.05-1.10, P < 0.0001], female sex (OR 2.5; 95% CI 1.4-4.8, P = 0.004), and unsuccessful cardioversion (OR 2.2; 95% CI 1.1-4.6, P = 0.03) were the independent predictors of bradycardic complications. Slow ventricular rate, use of digoxin, beta blocker, or antiarrhythmic medication did not increase the risk of bradycardic complications. Pacemaker was implanted in 24 (44.4%) patients after a median delay of 66 days.

Conclusion: Bradycardic complications are rare and usually benign after cardioversion of acute AF. They seem to reflect sinus node dysfunction and often result in later implantation of a permanent pacemaker.