Is atrial fibrillation associated with increased risk of stroke after transient ischaemic attack?

Abstract Background Atrial fibrillation(AF) is a critical cause of cardio-embolism in patients experiencing a transient ischaemic attack(TIA) or ischaemic stroke. However, real-world contemporary data on whether AF is associated with increased stroke risk after TIA is sparse. Purpose To examine whether AF is associated with stroke after first-time TIA. Methods We included all patients aged ≥18 years with first-time TIA from the Danish Stroke registry(2014-2020). The three-year cumulative incidences of stroke and all-cause mortality were compared between patients with and without AF using the Aalen-Johansen and Kaplan-Meier estimator. A multivariable cox-regression analysis was also performed, adjusting for the following variables: sex, age≥75 years, ischaemic heart disease, hypertension, diabetes, chronic renal disease, and calendar year. Results In total, we identified 21,613 patients with first-time TIA; 2,324 patients with AF and 19,289 patients without AF. Patients with AF were older (77.3 years [IQR:70.1-84.2] versus 70.0 years [IQR:59.8-77.8]), more often males(59.1% versus 52.4%), had more comorbidities, and received more medications e.g., oral anticoagulants(OAC) (64.2% versus 2.3%), compared to patients without AF at baseline. Furthermore, a higher proportion of patients with AF, compared to patients without AF, received OAC(71.0% versus 7.1%) and antihypertensives(46.8% versus 28.4%) within three months after discharge. Compared to patients with AF, a larger number of patients without AF received antiplatelet therapy e.g.,Acetylsalicylic acid(10.6% versus 22.2%) and Adenosine-diphosphate receptor inhibitors/Phosphodiesterase inhibitors(21.1% versus 80.7%) within three months after discharge. The three-year cumulative incidence of stroke after TIA was 5.8%(95% CI:[4.8-6.9]) in patients with AF and 4.1%(95% CI:[3.8-4.4]) in patients without AF(p<0.001). However, after accounting for potential confounders, AF was not independently associated with stroke after TIA (adjusted hazard ratio:1.18 [95% CI 0.96–1.45])(Figure1). Patient characteristics that were significantly associated with increased three-year stroke rate included male sex, age≥75 years, ischaemic heart disease, diabetes, and chronic renal disease. The three-year cumulative incidence of all-cause mortality after TIA was 24.7%(95% CI:[22.7–26.7]) in patients with AF and 10.0%(95% CI:[9.5–10.5]) in patients without AF(p<0.001). Conclusions In this nationwide study, we demonstrated that after accounting for patient characteristics, atrial fibrillation(AF) was not independently associated with stroke within three years following a transient ischaemic attack(TIA). However, male sex, age≥75 years, ischaemic heart disease, diabetes, and chronic renal disease were significantly associated with stroke after first-time TIA. These findings highlight the necessity for a thorough risk assessment and personalized preventive strategies to reduce the stroke-risk in patients with TIA.