External cardioversion of atrial fibrillation and flutter in patients with cardiac implantable electrical devices

Type of funding sources: None.Atrial tachyarrhythmias are often treated with external cardioversion (ECV) with direct current shocks in patients with potentially electrically sensitive cardiovascular implantable electronic devices (CIED). Long-term follow-up data on contemporary pacemakers and implantable cardioverter defibrillators (ICD) undergoing ECV is sparsely described. This study investigated shock-related complications and impact on CIEDs.All ECV procedures of atrial fibrillation and flutter from 2010 to 2020 in patients with CIED performed at a tertiary hospital (Denmark) were identified in the Danish National Patient Registry. Data on device interrogation before and after ECV and procedure-related complications were retrieved retrospectively by review of medical records.We analysed 664 ECV-events performed in 362 CIEDs, median implant time 1.5 year. Mean age of patients at first ECV-event were 69.4±9.7 years and 72.2\≤3 years after generator implant) following ECV. Minor shock-related device changes were found for impedances, atrial sensing values and pacing thresholds of right ventricle lead. In two cases increased pacing threshold of right ventricle leads following ECV triggered exit-blocks after few months. No patients died due to shock-related device dysfunctions.Following external cardioversion with transthoracic direct current shocks, sporadic (\lt;1\ but potentially critical changes in device function were identified in patients with contemporary pacemakers and implantable cardioverter-defibrillators. The present study suggests that routine post-cardioversion device interrogation is imperative for patient safety.