ABSTRACT NUMBER: ESOC2026A508 EFFECT OF ORAL ANTICOAGULATION ON STROKE RISK AFTER MYOCARDIAL INFARCTION DIFFERS BY THE PRESENCE OF ATRIAL FIBRILLATION

Abstract Background and aims Stroke risk remains elevated after myocardial infarction (MI). Oral anticoagulation (OAC) is recommended in survivors with atrial fibrillation (AF) and is also used in some patients without AF, for other indications such as left ventricular thrombus. However, whether OAC reduces stroke risk independently or only among patients with AF remains uncertain. This study examined whether the association between OAC and stroke risk after MI differs by AF history. Methods MI survivors from the national SWEDEHEART registry (Swedish Web-system for Evidence-based Care in Heart Disease) who attended a 6–10-week post-discharge follow-up between 2005 and 2020 were included. Fine–Gray competing-risk regression assessed associations between AF, OAC, and stroke, including interaction testing between AF and OAC. Results Among 85,360 MI survivors (mean age 64 ± 9 years, 74.3% men), 7,285 (8.5%) received OAC; 4,978 (68.3%) had AF and 2,307 (31.7%) did not. During follow-up, 4,275 (5.0%) experienced ischemic or hemorrhagic stroke. AF increased ischemic stroke risk (aHR 1.40, 95% CI 1.19–1.64), while OAC use alone showed no significant benefit (aHR 1.18, 95% CI 0.92–1.51). A significant AF–OAC interaction showed reduced ischemic stroke risk in patients with AF (aHR 0.56, 95% CI 0.41–0.77), with a similar trend for hemorrhagic stroke. Conclusions OAC was associated with reduced stroke risk in MI patients with AF, but not in those without AF. These findings highlight the absence of a stroke-preventive effect in non-AF patients and underscore the need to better understand the rationale for extended OAC use in this group. Conflict of interest Putu Ayuwidia Ekaputri: nothing to disclose; Adam Viktorisson: nothing to disclose; Petra Redfors: nothing to disclose. Margrét Leósdóttir: nothing to disclose. Katharina Stibrant Sunnerhagen: nothing to disclose.