Ischaemic stroke and intracerebral haemorrhage in the post-acute phase after myocardial infarction: a nationwide cohort study in Sweden

INTRODUCTION: Patients who survive myocardial infarction (MI) remain at risk of stroke in the post-acute MI-phase, after discharge. We investigated the incidence of ischaemic stroke and intracerebral haemorrhage in MI survivors attending early follow-up. PATIENTS AND METHODS: We included MI survivors from the SWEDEHEART registry linked to national health registers, who attended a cardiac rehabilitation visit 6-10 weeks post-MI between 2005 and 2020 and followed them until 31 December 2021. Fine-Grey competing-risk regression was used to assess associations between clinical factors and stroke outcomes. RESULTS: Among 85,360 MI survivors, 4275 patients experienced ischaemic stroke or intracerebral haemorrhage during follow-up. The incidence of ischaemic stroke was highest during the first year after MI (~1.1%) and declined thereafter, while intracerebral haemorrhage remained rare throughout follow-up. Reduced left ventricular ejection fraction (LVEF) was independently associated with higher ischaemic stroke risk. Compared with normal LVEF, patients with moderately reduced LVEF (30%-39%) had an sHR of 1.47 (95% CI, 1.14-1.90) at 1 year and 1.47 (95% CI, 1.25-1.74) at 5 years, while those with severely reduced LVEF (<30%) had an sHR of 1.62 (95% CI, 1.11-2.35) at 1 year and 1.32 (95% CI, 1.02-1.71) at 5 years. Atrial fibrillation (AF) was strongly and independently associated with ischaemic stroke risk (sHR 2.21; 95% CI, 1.70-2.88 at 1 year; sHR 1.54; 95% CI, 1.28-1.84 at 5 years). While oral anticoagulation alone was not associated with reduced stroke risk, it was associated with significantly lower ischaemic stroke risk among patients with AF (AF × oral anticoagulant interaction sHR 0.45; 95% CI, 0.27-0.75 at 1 year). CONCLUSION: Stroke risk after MI is highest during the first year and is strongly influenced by AF presence and reduced LVEF. These findings highlight the importance of early risk stratification and targeted prevention strategies after MI.