Association Between Epicardial Adipose Tissue Thickness and Early Arrhythmia Recurrence After Electrical Cardioversion for Atrial Fibrillation and Atrial Flutter in Patients With and Without Heart Failure—An Observational Study

Background and Objectives: Atrial fibrillation (AF) and atrial flutter are associated with significant morbidity. While electrical cardioversion (ECV) is a standard treatment for sinus rhythm restoration, early arrhythmia recurrence is common. Epicardial adipose tissue (EAT) is a metabolically active depot linked to atrial remodeling, yet its role in predicting post-ECV outcomes remains unclear. This study aimed to evaluate the association between EAT thickness measured by echocardiography and early arrhythmia recurrence following elective ECV in patients with and without heart failure (HF). Materials and Methods: A single-center observational study was conducted including 76 patients (38 with previously diagnosed HF) who underwent successful elective ECV (eECV) for AF or atrial flutter. Preprocedural transesophageal echocardiography was performed to exclude thrombi, while EAT thickness was assessed via transthoracic echocardiography (TTE). The primary outcome was early arrhythmia recurrence (within 30 days), and a secondary outcome was arrythmia recurrence in the HF subgroup. Data were analyzed using univariable and multivariable logistic regression, receiver operating characteristic (ROC) analysis, and subgroup analysis in patients with HF. Results: Arrhythmia recurrence occurred in 19 patients (25.0%) within the follow-up period. Mean EAT thickness did not differ significantly between patients with and without recurrence (3.74 ± 1.41 mm vs. 3.58 ± 1.78 mm; p = 0.42). EAT thickness did not emerge as a significant predictor of recurrence in univariable or multivariable models, demonstrating poor discriminative ability (AUC = 0.56). Similar findings were observed in the HF subgroup (OR = 0.94, p = 0.75; AUC = 0.49). Conversely, left atrial (LA) size was significantly associated with recurrence (OR = 2.76, p = 0.043). While EAT thickness correlated with body mass index and HF, it did not predict immediate rhythm outcomes. Conclusions: In our study, measurement of EAT thickness via TTE was not associated with early arrhythmia recurrence after eECV, including in patients with concomitant HF. These findings suggest that early post-cardioversion stability may depend more on established structural atrial remodeling, especially by LA enlargement, than on linear EAT thickness. Further research utilizing advanced volumetric imaging is warranted to clarify the role of epicardial adiposity in atrial arrhythmogenesis.