Abstract
BACKGROUND: Acute coronary syndrome (ACS) is frequently accompanied by newly diagnosed atrial fibrillation (AF). AIMS: We aimed to compare the risk of major adverse cardiovascular events (MACE) in ACS patients presenting with known, newly diagnosed, or no AF. METHODS: In our multicentre, prospective registry study, we included patients with confirmed ACS. Patients are classified as having known, newly diagnosed or no AF. Newly diagnosed AF is subdivided according to the duration of the episode, time of onset, post-coronary artery bypass graft (CABG) or spontaneous occurrence, and treatment with oral anticoagulants (OAC). The primary endpoint is MACE at 1 year. Key secondary endpoints include ischaemic stroke and bleeding complications. RESULTS: Amongst 4,433 patients with confirmed ACS, 3,598 (81.2%) had no AF, 438 (9.9%) had newly diagnosed AF, and 397 (9.0%) had known AF. The rates of OAC treatment at discharge were 53.4% in patients with newly diagnosed AF and 89.2% in patients with known AF. After adjusting for baseline imbalances, only new AF was independently associated with increased rates of MACE, whereas known AF was not (hazard ratio [HR] 1.52, 95% confidence interval [CI]: 1.19-1.90 and HR 0.93, 95% CI: 0.70-1.23). For ACS patients with newly diagnosed AF, episodes lasting >24 hours were associated with a higher risk of MACE compared to episodes <24 hours (HR 1.99, 95% CI: 1.36-2.93). Episodes of new AF occurring post-CABG had more favourable outcomes compared to spontaneously occurring new AF (HR for MACE 0.52, 95% CI: 0.31-0.86). OAC treatment rates were higher in the new AF subcategories with higher rates of MACE and ischaemic stroke. CONCLUSIONS: Newly diagnosed AF in ACS patients was associated with higher rates of MACE and ischaemic stroke compared to ACS patients without or with known AF. Among the ACS patients with new AF, an episode lasting >24 hours was associated with worse outcomes than shorter episodes, while post-CABG occurrence of AF showed relatively better outcomes compared to spontaneously occurring AF. Only 53% of new AF patients were discharged on OAC therapy versus 89% with known AF.