Short-duration atrial fibrillation in ischemic stroke : high risk despite subclinical burden : a prospective cohort study

Background and purpose: Atrial fibrillation (AF) episodes ≥ 30 s are currently considered clinically relevant in stroke diagnostics. However, shorter AF episodes may signal a significant embolic risk, especially in patients with embolic stroke of undetermined source (ESUS). This study investigates the prevalence, risk profile, and stroke severity associated with short-duration AF (SDAF < 30 s) across ischemic stroke subtypes. Methods: We prospectively enrolled 714 consecutive patients with ischemic stroke or Transient ischemic attacks who underwent ≥ 48-hour ECG monitoring. AF episodes were classified as 0–14 s, 15–29 s, or ≥ 30 s. Stroke subtypes were defined using TOAST and ESUS criteria. Risk profiles, NIH Stroke Scale scores, and CHA₂DS₂-VASc scores were analyzed by AF duration. Results: AF of any duration was detected in 53.8% of patients; 22.8% had episodes ≥ 30 s and 29.9% had SDAF. Among ESUS patients, 35.7% exhibited SDAF, and 80.2% of these had CHA₂DS₂-VASc scores ≥ 2. Stroke severity and risk scores were significantly higher in patients with SDAF than those without AF. SDAF was more prevalent in women (37.0%) and in individuals aged > 65 years (89.4%). Conclusions: SDAF is common across stroke subtypes—particularly ESUS—and is associated with elevated thromboembolic risk despite falling below current diagnostic thresholds. These findings highlight a diagnostic blind spot in stroke workup and support reevaluation of duration-based criteria for post-stroke AF detection and risk profiling.