INTRODUCTION: We investigated the burden of microembolic signals (MES) in patients with acute ischaemic stroke (AIS) and atrial fibrillation (AF), assessing their impact on functional outcomes. PATIENTS AND METHODS: This multicentre international prospective cohort study involved patients with AIS and either a known or newly diagnosed anticoagulant-naïve AF. All centres utilised the same transcranial Doppler machine for 1-h monitoring with bilateral 2 MHz probes within 24 h of symptom onset. Recordings underwent MES analysis by a blinded central reader. The primary objectives were to ascertain the MES proportion and its association with functional outcomes assessed by the modified Rankin scale (mRS) score at 90 days. RESULTS: Between September 2019 and May 2021, we enrolled 61 patients, with a median age of 78 years (interquartile range 73-83) and a median stroke severity score of 11 (interquartile range 4-18). MES were observed in 14 patients (23%), predominantly unilateral (12/14, 86%), with a median rate of 6 counts/hour (interquartile range 4-18). MES occurrence was higher post-thrombectomy and among those with elevated brain natriuretic peptide levels (p < 0.05). A worse mRS score of 3-6 was more frequent in patients with MES, occurring in 11/14 (79%), compared to those without MES, 20/47 (43%), with an adjusted odds ratio of 5.04 (95% CI, 1.15-39.4), p = 0.04. CONCLUSIONS: Nearly a quarter of patients with AIS and AF exhibited silent microembolization after the index event. Detecting MES within 24 h post-stroke (using transcranial Doppler) could signify a marker of poor functional outcomes. Subsequent trials will assess if very early antithrombotic treatment might enhance outcomes in this highly selective group of cardioembolic stroke patients. (Clinicaltrials.gov ID: NCT06018090).

Center for Health Research Faculty of Medicine University of Ostrava Ostrava Czech Republic

Department of Clinical Neurosciences and Mental Health Faculty of Medicine of University of Porto Porto Portugal

Department of Neurology Centro Hospitalar de São João Faculty of Medicine of University of Porto Portugal

Department of Neurology Centro Hospitalar Universitário de São João Faculty of Medicine of University of Porto Porto Portugal

Department of Neurology Hospital Centre Zagreb Zagreb Croatia

Justus Liebig University Giessen Giessen Germany

Stroke Unit and Neurosonology Laboratory University of Padua School of Medicine Padova Italy

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