Most clots retrieved from patients with acute ischemic stroke are 'red' in color.
'White' clots represent a less common entity and their histological composition is
less known. Our aim was to investigate the composition, imaging and procedural characteristics
of 'white' clots retrieved by mechanical thrombectomy.Seventy five 'white' thrombi
were selected by visual inspection from a cohort of 760 clots collected as part of
the RESTORE registry. Clots were evaluated histopathologically.Quantification of Martius
Scarlett Blue stain identified platelets/other as the major component in 'white' clots'
(mean of 55% of clot overall composition) followed by fibrin (31%), red blood cells
(6%) and white blood cells (3%). 'White' clots contained significantly more platelets/other
(p<0.001*) and collagen/calcification (p<0.001*) and less red blood cells (p<0.001*)
and white blood cells (p=0.018*) than 'red' clots. The mean platelet and von Willebrand
Factor expression was 43% and 24%, respectively. Adipocytes were found in four cases.
'White' clots were significantly smaller (p=0.016*), less hyperdense (p=0.005*) on
computed tomography angiography/non-contrast CT and were associated with a smaller
extracted clot area (p<0.001*) than 'red' clots. They primarily caused the occlusion
of middle cerebral artery, were less likely to be removed by aspiration and more likely
to require rescue-therapy for retrieval.'White' clots represented 14% of our cohort
and were platelet, von Willebrand Factor and collagen/calcification-rich. 'White'
clots were smaller, less hyperdense, were associated with significantly more distal
occlusions and were less successfully removed by aspiration alone than 'red' clots.
