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Introduction Direct current (DC) cardioversion is an effective intervention for restoring sinus rhythm in patients presenting with atrial fibrillation or flutter (AF), but early recurrence remains a common problem. Current guidelines recommend consideration of amiodarone as adjunct therapy in patients in whom a high rate of AF recurrence is predicted. However, there is no clear consensus on which patients should receive amiodarone therapy. Instead, guidelines recommend that it should be considered on a case-by-case basis with shared decision making between patient and clinician. In practice, clinicians may opt to pre-treat with amiodarone in patients requiring repeat DC cardioversion, especially in the presence of other adverse characteristics such as longer duration of AF, and reduced left ventricular ejection fraction (LVEF). Given concerns about its unfavourable side effect profile, amiodarone use remains limited and variable, and more data is required to elucidate its benefits and risks in this patient population.Methods We performed a retrospective analysis of 193 consecutive patients who underwent elective DC cardioversion for AF in March 2023 or earlier. Baseline characteristics including demographic data, echocardiographic findings, AF duration, number of previous DC cardioversions and medications were documented. Patients were followed up at 6 weeks and 12 months. We compared patient characteristics and rate of maintenance of sinus rhythm between patients treated with amiodarone and those without. Chi-squared and Fisher exact tests were performed for categorical variables and Student’s t-test for continuous variables. Side effects from amiodarone therapy were documented.Results 25 patients (13.0%) were started on amiodarone prior to DC cardioversion. Patients on amiodarone were more likely to have had at least one previous failed DC cardioversion (60.0% vs 21.4%, p<0.001), AF duration of twelve months or more (84.0% vs 53.0%, p=0.003), LVEF of less than 40% (32.0% vs 14.3%, p=0.03), and coronary artery disease (32.0% vs 13.7%, p=0.02). Amiodarone therapy was not associated with increased rate of acute restoration of sinus rhythm (96.0% vs 92.3%, p=0.50), but was associated with maintenance of sinus rhythm at 6 weeks (92.0% vs 54.8%, p<0.001) and 12 months (60.0% vs 26.8%, p<0.001). Six patients on amiodarone (24.0%) experienced amiodarone-related side effects within the eighteen-month follow-up period. The most common side effect was thyroid dysfunction (50.0%).Conclusions Amiodarone is effective in promoting maintenance of sinus rhythm following elective DC cardioversion for AF. This effect is demonstrated even among patients who have had a previous failed DC cardioversion and other risk factors for AF recurrence, including longer duration of AF and reduced LVEF. More research is warranted to elucidate the factors that predict patients most likely to benefit overall from amiodarone therapy, given its known side effect profile.Abstract 4-012 Table 1Comparison of patient characteristics pre-DC cardioversion (DCCV) Amiodarone (n=25) Not on amiodarone (n=168) p Baseline characteristics Age (years), mean (±SD)BMI (kg/m2), mean (±SD) 69.2 (±9.2)31.9 (±7.5) 66.0 (±9.8)30.0 (±5.7) 0.060.11 Echocardiographic findings LVEF <40%, n (%)LA dilatation, n (%) 8 (32.0)19 (76.0) 24 (14.3)120 (71.4) 0.030.63 AF characteristics AF duration ≥12 months, n (%)≥1 prior DCCVs, n (%) 21 (84.0)15 (60.0) 89 (53.0)36 (21.4) 0.003<0.001 Co-morbidities Coronary artery disease, n (%)Hypertension, n (%)OSA, n (%) 8 (32.0)14 (56.0)3 (12.0) 23 (13.7)81 (48.2)11 (6.5) 0.020.470.33 Abstract 4-012 Figure 1