Effect of Clot Burden Score on Safety and Efficacy of Intravenous Alteplase Prior to Mechanical Thrombectomy in Acute Ischemic Stroke: A Subgroup Analysis of a Randomized Phase 3 Trial

BACKGROUND AND PURPOSE:

Whether thrombus burden in acute ischemic stroke modify the effect of intravenous thrombolysis (IVT) before mechanical thrombectomy (MT) remains uncertain. We aim to investigate the treatment effect of stratified clot burden score (CBS) on the efficacy and safety of direct versus bridging MT.

MATERIALS AND METHODS:

This is an exploratory subgroup analysis of a randomized trial evaluating the effect of CBS on clinical outcome in the DIRECT-MT trial. CBS was divided into 3 groups (0–3, 4–6, and 7–10) based on preoperative CTA, where higher scores indicated a lower clot burden. We report the adjusted common odds ratio for a shift toward better outcomes on the mRS after thrombectomy alone compared with combination treatment by stratified CBS groups.

RESULTS:

No modification effect of mRS distribution was observed by CBS subgroups (CBS 0–3: adjusted common ratio odds 1.519 [95% CI, 0.928–2.486]; 4–6: 0.924 [0.635–1.345]; 7–10: 1.040 [0.481–2.247]). Patients with CBS 4–6 had a higher rate of early reperfusion (adjusted OR (aOR), 0.3 [95% CI, 0.1–0.9]), final reperfusion (aOR 0.5 [95% CI, 0.3–0.9]), and fewer thrombectomy attempts (aOR 0.4 [95% CI, 0.1–0.7]). Patients with CBS 7–10 had a higher rate of asymptomatic intracranial hemorrhage (14.9% versus 36.8%, P = .0197) for bridging MT. No significant difference was observed in other safety outcomes by trichotomized CBS.

CONCLUSIONS:

The subgroup analysis of DIRECT-MT suggested that thrombus burden did not alter the treatment effect of IVT before MT on functional outcomes in CBS subgroups.