White Blood Cell Subtypes as Biomarkers for Stroke Etiology in Acute Ischaemic Stroke Clots Retrieved by Mechanical Thrombectomy

Abstract

Slow thrombus formation in cardioembolic stroke cases and high sheer volume of blood in the environment where large artery atherosclerosis thrombi are formed may cause variabilities in their histological composition. For inflammatory cells, an increase in neutrophils is associated with left atrial thrombus, while macrophages are associated with plaque instability and thrombus formation. We hypothesized that different white blood cell subtypes in acute ischaemic stroke (AIS) clots may vary according to the stroke etiology.

We investigated the histological composition and the white blood cell subtype composition of AIS clots, correlated with stroke etiology.

AIS clots from 50 cardioembolic cases and 50 large artery atherosclerosis (LAA) cases were collected per pass. The clot sections were stained with Martius scarlet blue to assess histological composition. Immunohistochemistry was used to assess white blood cell (WBC) subtypes (neutrophils, lymphocytes and macrophages). The effect of etiology on clot area, clot fragmentation and revascularization outcome were also assessed. Finally, 50 clots of unknown etiology were compared to the cardioembolic and LAA cohorts.

No statistically significant effect of etiology on clot composition was observed. There was a strong trend indicating that LAA clots were larger than cardioembolic clots. Larger clots were significantly richer in red blood cells and smaller clots were significantly richer in fibrin and platelets. significantly higher number of cardioembolic cases had good revascularization outcome compared to LAA. No statistically significant effect found of thrombolysis on clot composition. The clots of unknown etiology most closely resembled cardioembolic clots.

No statistically significant differences in the expression of neutrophils, lymphocytes or macrophages were found between cardioembolic and LAA etiologies. Trends were noted, as cardioembolic clots expressed more neutrophils and lymphocytes, while LAA clots had the highest macrophage expression.

Further studies with a larger cohort could provide more firm conclusions on the possibility of WBC subsets being a reliable marker for stroke etiology.