Mind the Gap: Recurrence of Sex-Related Differences in Patients with Acute Atrial Fibrillation in the Emergency Department—A Retrospective Cohort Study

<b>Background/Objectives</b>: In recent years, awareness of sex disparities in atrial fibrillation (AF) and atrial flutter (AFL) has grown, resulting in significant advancements in sex-specific treatment strategies. As these treatment approaches continue to evolve, it is essential to remain attentive to sex-related issues to ensure equitable care for all patients, a point first emphasised by the 2016 AF guidelines. Our objective was the long-term evaluation of sex-specific treatment standards for acute AF/AFL. <b>Methods</b>: This cohort study included cases of acute AF/AFL treated in the emergency department of the Medical University of Vienna, Austria, between 2012 and 2022. The Kaplan-Meier method was used to analyse time-to-event data. The effect of sex on the time to restoration of sinus rhythm was assessed using the log-rank test for unadjusted models and the likelihood ratio test for adjusted models. The groups were categorised based on cases occurring before and after 2016. <b>Results</b>: A total of 3661 cases (55.7% male) were analysed. Before 2016, sinus rhythm was achieved in 70.8% of males and 71.2% of females; after 2016, these rates were 71.8% and 68.6%, respectively. The adjusted model showed a significant effect of sex on the time to restoration of sinus rhythm after 2016 (<i>p</i> = 0.013) but not before (<i>p</i> = 0.865). A subgroup analysis indicated similar results for pharmacologic rhythm control (<i>p</i> = 0.035 vs. <i>p</i> = 0.193). A sensitivity analysis confirmed robustness, with similar effects in both models. The success rate of pharmacological cardioversion was lower in women than in men but was used more frequently in women after 2016. <b>Conclusions</b>: The re-emergence of a sex gap in success rates and time to restoration of sinus rhythm in emergency treatment for acute AF/AFL is concerning and necessitates a re-evaluation of treatment protocols, improved decision-making processes, and further research to ensure equitable, effective, and safe emergency care for all patients.