Extracellular vesicles in atrial fibrillation and stroke

Background: Atrial fibrillation (AF) is associated with a 5-fold increased risk of thromboembolic stroke. Extracellular vesicles (EVs) convey pathophysiological information and are possible biomarkers for risk of stroke.

Methods: EVs were measured in 836 patients with AF (of which 280 were stroke cases) selected from the ARISTOTLE trial and in a cohort of unselected 70 year old individuals (n = 1007, reference material). EVs from platelets, leukocytes, erythrocytes and inflammatory endothelial cells were measured using flow cytometry and a solid-phase proximity ligation assay.

Results: Concentrations of EVs were higher in the ARISTOTLE patients than in the PIVUS cohort for all the EV groups except EVs from endothelial cells (p < 0.0001). The distributions of the concentrations of the EVs were similar among the control group and the stroke cases for all of the sources of EVs in the ARISTOTLE study. EVs were modestly correlated with the levels of NT-ProBNP, Cystatin C, GDF-15 and D-dimer. Stronger correlations were found for platelet EVs as well as phosphatidyl serine positive EVs that were correlated with CD40 ligand in the ARISTOTLE study. Leukocyte EVs were correlated with IL-6 in both the ARISTOTLE and the PIVUS study, implicating them in different physiological processes.

Conclusions: Higher levels of EVs were found in anticoagulated patients with AF and a higher risk of stroke than in a general population of similar age, possibly due to the high disease burden in AF patients. Our data with EVs representing a broad repertoire of activated blood cells in AF patients suggest that EVs are likely not a key mediator of occurrence of stroke in this population.