Slow Collateral Flow Is Associated with Thrombus Extension in Patients with Acute Large-Artery Occlusion

BACKGROUND AND PURPOSE: It is still poorly understood about the dynamic changes of the thrombus after intravenous thrombolysis and how the remaining thrombus affects clinical outcome in human stroke. Collateral flow was assumed to help to deliver endo/exogenous tissue-type plasminogen activator to the clot. We aimed to analyze the impact of collateral flow on the dynamic changes of the thrombus in patients with acute large-artery occlusion who received intravenous thrombolysis.

MATERIALS AND METHODS: We reviewed consecutive patients with acute ischemic stroke with M1 segment or distal internal carotid artery occlusion who underwent multimodal MR imaging or CT perfusion before and 24 hours after intravenous thrombolysis without recanalization. Patients were divided into 3 groups (thrombus extension, shortening, and no change) according to thrombus-length change between baseline and 24 hours. Collateral flow was measured with arrival time delay and the collateral scoring system. Poor outcome was defined as a 3-month modified Rankin Scale score of ≥3.

RESULTS: Among 51 patients, 18 (35.3%) had thrombus extension, 14 (27%) had thrombus shortening, and 19 (37.3%) had thrombus without change. Arrival time delay was independently associated with thrombus extension (OR = 1.499; 95% CI, 1.053–2.135; P = .025). Similarly, the collateral score on the peak artery phase was independently associated with thrombus extension (OR = 0.456; 95% CI, 0.211–0.984; P = .045), whereas baseline National Institutes of Health Stroke Scale score (OR = 0.768; 95% CI, 0.614–0.961; P = .021) and baseline thrombus length (OR = 1.193; 95% CI, 1.021–1.394; P = .026) were associated with thrombus shortening. All patients with thrombus extension had poor outcomes.

CONCLUSIONS: Slow collateral flow was related to thrombus extension in patients with large-artery occlusion without recanalization after intravenous thrombolysis.