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Introduction Atrial flutter (AFL) and atrial fibrillation (AF) are common arrhythmias that often require electrical cardioversion (DCCV) for rhythm control. While DCCV is generally safe, post-procedural bradyarrhythmias, including sinus bradycardia, junctional bradycardia, and atrioventricular (AV) blocks, are potential complications that may complicate patient recovery. The risk of bradyarrhythmia may be influenced by the use of antiarrhythmic drugs (AADs) such as beta-blockers, amiodarone, flecainide, calcium channel blockers, and digoxin, which are commonly prescribed for rhythm management in these patients [1]. This study aims to investigate the incidence of post-DCCV bradyarrhythmias and evaluate the impact of different AADs on this outcome.Methods A cross-sectional study was conducted on 194 patients with documented AFL or AF who underwent DCCV at a secondary care cardiac centre between March 2021 and March 2023. Patients were classified based on their prescribed antiarrhythmic therapy prior to DCCV, which included beta-blockers, amiodarone, flecainide, calcium channel blockers, and digoxin ( figure 1). The primary outcome was the incidence of post-DCCV bradyarrhythmia, which was defined as the development of sinus bradycardia, junctional bradycardia, or any degree of AV block within 24 hours after the procedure. Multivariate logistic regression was used to assess the association between AAD use and the occurrence of bradyarrhythmias, adjusting for potential confounders such as age, sex, comorbidities, and baseline heart rate.Abstract 4-010 Figure 1Distribution of AAD among the study populationResults The overall incidence of post-DCCV bradyarrhythmia in the study cohort was 3.63%. Among the different AADs, only amiodarone was associated with a significantly increased incidence of bradyarrhythmia (57.14%) compared to the other antiarrhythmic classes (p<0.001) ( table 1). The incidence of bradyarrhythmia in patients on beta-blockers, flecainide, calcium channel blockers, and digoxin did not differ significantly from those not receiving AAD therapy (p>0.05 for all). Multivariate logistic regression analysis, adjusted for potential confounders, revealed that amiodarone use was independently associated with a higher risk of post-DCCV bradyarrhythmia (hazard ratio 8.85; 95% CI 1.84–42.7, p=0.007). No significant interactions were found between age, sex, or comorbidity status and the risk of bradyarrhythmia.Abstract 4-010 Table 1The incidence of bradyarrhythmia in the different AAD groups Drug % of patients on the medication p value Beta blockers 4.24% 0.267 Calcium channel blockers 0% 0.31 Amiodarone 16% <0.001 Flecainide 0% 0.4 Digoxin 3.8% 0.95 Conclusions This study demonstrates that the incidence of post-DCCV bradyarrhythmia in patients with AFL and AF is relatively low (3.63%), but the risk is significantly higher in those receiving amiodarone. Amiodarone use was associated with an eight-fold increase in the likelihood of post-procedural bradyarrhythmias, which has important implications for the management of these patients. Clinicians should consider the risk of bradyarrhythmia when prescribing amiodarone, especially in patients undergoing DCCV. Further studies are required to better understand the mechanisms behind amiodarone-associated bradyarrhythmias and to explore strategies to mitigate this risk (Kanelidis et al., 2016; Mantica et al., 2019).References Rasmussen P, Dalgaard F, Pallisgaard J, Gislason G, Ruwald M, Torp-Pedersen C, Hansen M. Anti-arrhythmic drugs confer increased risks of bradyarrhythmia in patients undergoing direct current cardioversion for atrial fibrillation. Eur Heart J. 2020; 41: 10.1093/EHJCI/EHAA946.0554.