Di Dalmazi G, Vicennati V, Pizzi C, et al. - Researchers conducted this retrospective study to examine prevalence and incidence of atrial fibrillation (AF) in a large cohort of patients with autonomous cortisol secretion (ACS). Patients assessed for adrenal incidentalomas (n = 632) between 1990 and 2018, without pheochromocytoma, primary aldosteronism, Cushing syndrome, congenital adrenal hyperplasia, and adrenal malignancy. Prevalence and incidence of AF was the main outcome measure. The prevalence of AF in ACS patients (8.5%) was higher than NST (3.1%) and in the general population. Data reported that the age-adjusted rate ratio to the general population was 1.0 for NST and 2.6 for ACS. ACS demonstrated a higher risk of incident AF than NST associated with postdexamethasone cortisol, independent of identified contributing factors. AF is at risk in patients with adrenal incidentalomas and ACS. Follow-up monitoring of ECGs can be recommended.