Effect of Amiodarone after Catheter Ablation According to Left Atrial Structure and Function: The AMIO-CAT Trial

Catheter ablation (CA) is commonly used to obtain rhythm control in patients with atrial fibrillation (AF), yet AF recurrence is frequent. In this study, we hypothesized that measures of left atrial (LA) structure and function modified the treatment effect of amiodarone to prevent AF recurrence, which has otherwise not proven beneficial. This was a post hoc analysis of the double-blinded AMIO-CAT trial. Patients undergoing CA were randomized to short-term amiodarone treatment or placebo. All patients underwent echocardiography to assess LA volumes and strain. The primary endpoint was AF recurrence at 6-months. Secondary endpoints were cardioversion and AF-related hospitalization during follow-up. Of 212 patients, 108 were randomized to amiodarone and 104 to placebo. 206 patients were eligible for analyses of the primary endpoint, of whom 90 (44%) developed AF recurrence. No measure of LA size or function significantly modified the effect of amiodarone for preventing AF recurrence (p for interaction >0.05 for all measures). However, abnormal LA strain (<22.7%) significantly modified the treatment effect for the secondary outcomes of cardioversions (p for interaction = 0.013) and AF-related hospitalization (p for interaction = 0.014). In patients with abnormal LA strain, amiodarone significantly reduced the risk of cardioversions (OR 0.35 [0.15 to 0.80], p = 0.013) and AF-related hospitalization (OR 0.31 [0.14 to 0.73], p = 0.007) compared to placebo. In conclusion, LA measures did not modify the treatment effect of amiodarone versus placebo for preventing AF recurrence at 6 months in patients undergoing CA. However, in patients with abnormal LA strain, amiodarone may reduce cardioversions and AF-related hospitalizations as compared to placebo. Clinical trial registration: Clinicaltrials.gov unique identifier: NCT00826826.