Outpatient Electrical Cardioversion of Atrial Fibrillation: 8 Years' Experience. Analysis of Shock-Related Arrhythmias

Background: Outpatient electrical cardioversion (EC) of atrial fibrillation is currently the standard of care. Shock‐related arrhythmias may be particularly deleterious in this setting. Preoperative identification of high‐risk patients may be very useful. Methods: A retrospective analysis was made of 543 consecutive elective EC procedures in 457 outpatients over an 8‐year period in a university cardiological institute. The protocol included adequate anticoagulation, intravenous anesthesia, direct current shock, and a direct observation after a shock to detect procedure‐related complications. No patients were excluded due to severity of pathology or comorbidities. Clinical characteristics, energy delivered, medications, arrhythmic phenomena, and predictors of success and complications were analyzed. Results: Of 543 ECs performed, 88.2% restored sinus rhythm, which persisted at discharge in 83.2%. No anesthesia‐related complications were detected. No thromboembolic complications were detected. Use of a biphasic cardioverter was the only predictor of success (P = 0.0001). The bradyarrhythmic complication rate was 1.5%. No ventricular arrhythmic events were detected. Atrial flutter was present in five of eight patients who developed complications versus 44 of 535 patients who had no complications (P < 0.0005), and prosthetic heart valves in four of eight complicated versus 40 of 535 uncomplicated cases (P = 0.0044). The combination of atrial flutter and prosthetic heart valve was found in four of eight complicated versus 11 of 535 uncomplicated cases (P < 0.0005). Conclusion: Shock‐related arrhythmias are essentially bradyarrhythmias. Atrial flutter and previous cardiac surgery identify a subgroup of patients at high risk of postshock bradyarrhythmic complications.