Effectiveness of cardiac Holter monitoring for more than four weeks for the detection of occult atrial fibrillation in embolic stroke of undetermined source

BACKGROUND: Hidden atrial fibrillation (AF) is considered a major contributor to embolic strokes of undetermined source (ESUS). Prolonged cardiac monitoring is effective for detecting AF, especially when started soon after stroke onset. METHODS: This prospective multicentre study evaluated the rate of AF detection in ESUS patients under real-world clinical conditions using wearable Holter cardiac monitoring for 30 days. RESULTS: A total of 352 patients were included. The mean age was 67.8 years, and 46% were women. The AF detection rate was 17.1%, with a mean episode duration of 401.7min. Compared with patients without AF, those with AF were older (72.2 vs 67.0 years; mean difference, 5.16 years; 95% CI, 2.24-8.09; p=0.0012), had a higher frequency of large vessel occlusion (35.9% vs 17.0%; OR, 2.66; 95% CI, 1.40-5.05; p=0.002), showed larger left atrial diameter (40.4 vs 38.1mm; mean difference, 2.25mm; 95% CI, 0.56-3.95; p=0.013), and more often had excessive supraventricular ectopic activity on 24-hour Holter monitoring (37.5% vs 20.5%; OR, 2.33; 95% CI, 1.26-4.32; p=0.006). Notably, 73.3% of AF cases were detected during monitoring initiated within the first 6 months after stroke onset. CONCLUSIONS: These findings support the potential clinical utility of 30-day prolonged cardiac monitoring to detect AF in ESUS patients, highlighting its value in etiological stroke assessment in real-world clinical practice, with greater efficacy during the first 30 days, but also in cases where monitoring is initiated months after the event.