Luciano A. Sposato

BACKGROUND: Ischemic stroke and transient ischemic attack (TIA) standard-of-care etiological investigations include an ECG and prolonged cardiac monitoring (PCM). Atrial fibrillation (AF) detected after stroke has been generally considered a single entity, regardless of how it is diagnosed. We hypothesized that ECG-detected AF is associated with a higher risk of stroke recurrence than AF detected on 14-day Holter (PCM-detected AF). METHODS: We conducted a retrospective, registry-based, cohort study of consecutive patients with ischemic stroke and TIA included in the London Ontario Stroke Registry between 2018 and 2020, with ECG-detected and PCM-detected AF lasting ≥30 seconds. We quantified PCM-detected AF burden. The primary outcome was recurrent ischemic stroke, ascertained by systematically reviewing all medical records until November 2022. We applied marginal cause–specific Cox proportional hazards models adjusted for qualifying event type (ischemic stroke versus TIA), CHA₂DS₂-VASc score, anticoagulation, left ventricular ejection fraction, left atrial size, and high-sensitivity troponin T to estimate adjusted hazard ratios for recurrent ischemic stroke. RESULTS: We included 366 patients with ischemic stroke and TIA with AF, 218 ECG-detected, and 148 PCM-detected. Median PCM duration was 12 (interquartile range, 8.8–14.0) days. Median PCM-detected AF duration was 5.2 (interquartile range, 0.3–33.0) hours, with a burden (total AF duration/total net monitoring duration) of 2.23% (interquartile range, 0.13%–12.25%). Anticoagulation rate at the end of follow-up or at the first event was 83.1%. After a median follow-up of 17 (interquartile range, 5–34) months, recurrent ischemic strokes occurred in 16 patients with ECG-detected AF (13 on anticoagulants) and 2 with PCM-detected AF (both on anticoagulants). Recurrent ischemic stroke rates for ECG-detected and PCM-detected AF groups were 4.05 and 0.72 per 100 patient-years (adjusted hazard ratio, 5.06 [95% CI, 1.13–22.7]; P =0.034). CONCLUSIONS: ECG-detected AF was associated with 5-fold higher adjusted recurrent ischemic stroke risk than PCM-detected AF in a cohort of ischemic stroke and TIA with >80% anticoagulation rate.