Di Dalmazi G, Vicennati V, Pizzi C, et al. - Researchers conducted this retrospective study to examine the prevalence and incidence of atrial fibrillation (AF) in a large cohort of patients with autonomous cortisol secretion (ACS). Between 1990 and 2018, patients assessed for adrenal incidentalomas (n = 632), without pheochromocytoma, primary aldosteronism, Cushing syndrome, congenital adrenal hyperplasia, and adrenal malignancy. Among patients with ACS, AF incidence was higher than in nonsecreting tumors (NST), and the general population. For the general population, the age-adjusted rate ratio 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. Adrenal incidentalomas and ACS patients are at risk for AF. Electrocardiogram monitoring can be advised during follow-up.