Background:
Although atrial fibrillation (AF) comes to mind as the origin of ESUS (Embolic Stroke of Undetermined Source) subjects, recent clinical trials with direct oral anticoagulation raise suspicions on the heterogeneity of ESUS. 
The clinical, radiological and prognostic characteristics of ESUS subjects with high aetiological suspicion of AF are established.

Method:
176 ischemic stroke patients were studied. 78 of them, had a newly diagnosed with AF (nAF) and 98 subjects were met ESUS criteria. Biomarkers (BK) as NSE, IL-6, NT-proBNP, hs-troponin, hs-CRP were assessed. 
Clinical, radiological characteristics and prognosis, using the modified Rankin scale (mRS) at 7 and 90 days, were compared in ESUS patients according to BK.

Results:
nAF subjects had greater levels of IL-6, NT-proBNP, hs-CRP and hs-troponin than ESUS subjects (p0.001). NT-proBNP demostrated better discrimination for AF (AUC 0.73; CI 95% (0.66-0.81) p<0.001). A cut-off of 215pg/ml with negative predictive value 88.6% was established. 
Up to 60% of ESUS subjects had levels of NT-proBNP≥215pg/ml. These were older (76.3 vs. 64.8 years; p<0.001). The CHA2D2-VASC score was higher in ESUS subjects with NT-proBNP≥215pg/ml (5 vs. 4; p<0.001). Greater stroke severity, measured by NIHSS (7 vs. 4; p0.037), and a worse 7-day prognosis were presented in ESUS subjects with NT-proBNP≥215pg/ml (2.5 vs. 1; p0.024). The scattered one territory pattern was greater in subjects with NT-proBNP≥215pg/ml (46.9% vs. 25%; p0.028). 

Conclusion:
ESUS subjects with NT-proBNP≥215pg/ml present similar characteristics to cardioembolic stroke patients. These subjects would benefit from further study to detect AF.

BIOMARKERS AS ANALYTIC TOOL TO DIFFERENTIATE SUBGROUPS AMONG ESUS PATIENTS