Prognosis and antithrombotic practice patterns in patients with recurrent and transient atrial fibrillation following acute coronary syndrome: A nationwide study

First-time detected atrial fibrillation (AF) is associated with aggravated prognosis in patients admitted with acute coronary syndrome (ACS). Yet, among patients surviving beyond one year after ACS, it remains unclear how the recurrence of AF within the initial year after ACS affects the risk of stroke. With Danish nationwide data from 2000 to 2021, we identified all patients with first-time ACS who were alive one year after discharge (index date). Patients were categorized into: i) no AF; ii) first-time detected AF during ACS admission without a recurrent hospital contact with AF (transient AF); and iii) first-time detected AF during ACS admission with a subsequent recurrent hospital contact with AF (recurrent AF). From index date, two-year rates of ischemic stroke were compared using multivariable adjusted Cox regression analysis. Treatment with antithrombotic therapy was assessed as filled prescriptions between 12 and 15 months following ACS discharge. We included 139,137 patients surviving one year post ACS discharge: 132,944 (95.6%) without AF, 3920 (2.8%) with transient AF, and 2273 (1.6%) with recurrent AF. Compared to those without AF, the adjusted two-year hazard ratios of ischemic stroke were 1.45 (95% CI, 1.22–1.71) for patients with transient AF and 1.47 (95% CI: 1.17–1.85) for patients with recurrent AF. Prescription rates of oral anticoagulation increased over calendar time, reaching 68.3% and 78.7% for transient and recurrent AF, respectively, from 2019 to 2021. In patients surviving one year after ACS with first-time detected AF, recurrent and transient AF were associated with a similarly increased long-term rate of ischemic stroke. •In patients experiencing first-time AF, roughly one-third had a recurrent AF hospital contact within the first year of ACS. Meanwhile, two-thirds were classified as having ‘transient AF’ since they did not have any hospital contacts related to AF during this period.•Transient and recurrent AF was associated with similarly increased long-term rates of ischemic stroke and mortality.•Between 12 and 15 months after ACS discharge, 64% and 78% of patients with transient and recurrent AF, respectively, were in OAC treatment at the end of the study period (2019–2021).