Abstract TP246: Circadian Variability of the Clot Burden Score in Acute Anterior Circulation Ischemic Stroke

Abstract

Background/Purpose: Fibrinolytic activity in blood plasma displays a circadian rhythm with a drop in the morning hours that may predispose to acute thrombotic events. The Clot Burden Score (CBS) is a semiquantitative measure on CT angiography (CTA) of thrombus extent in proximal anterior circulation strokes that has been correlated with functional outcome. Higher clot burden has also been shown to have lower recanalization rates with intravenous thrombolytics. We aimed to investigate whether CBS is a parameter that displays circadian variability. Methods: We performed a retrospective analysis on consecutive stroke patients presenting <24 hours from symptom onset or last known well (LKW) with an occlusion in the anterior circulation confirmed on CTA. CBS was scored on a 10-point negative ordinal scale with 2-points subtracted for occlusion of the supraclinoid ICA, proximal M1, or distal M1, and 1-point subtracted for occlusion of the infraclinoid ICA, A1, or either M2 branches. No points were subtracted for occlusion distal to A1 or M2. Subjects were grouped into four 6-hour intervals, MORNING: 6:00-11:59, DAY: 12:00-17:59, EVENING: 18:00-23:59, and NIGHT: 0:00-5:59, based on the time of onset/LKW. CBS values were compared between groups using the Kruskal-Wallis test with pairwise comparisons. Results: 240 subjects were included with median age of 75 (IQR 65-84), NIHSS score of 17 (IQR 10-24), and time from onset/LKW to CTA of 5 hours (IQR 2-11). 73 subjects had onset during the MORNING, 56 during the DAY, 86 during the EVENING, and 25 during the NIGHT. The median CBS from MORNING time onset was 6 (IQR 5-9), compared to 7 (IQR 6-9) from the DAY, 7.5 (IQR 6-9) from the EVENING, and 7 (IQR 5-8.5) from the NIGHT. CBS was significantly lower in the MORNING compared to the EVENING, p=0.037. CBS was not significantly different between all other pairwise comparisons, p>0.107. Conclusion: CBS as a measure of thrombus extent in proximal anterior circulation strokes on CTA appears to show circadian variability, with lower scores (higher clot burden) during MORNING onset (6:00-11:59) than the EVENING (18:00-23:59). This may have implications for future studies of chronotherapeutic protocols.