Clot Burden Score and Collateral Status and Their Impact on Functional Outcome in Acute Ischemic Stroke

Abstract

Background and purpose: Collateral status and thrombus length have been independently associated with functional outcome in patients with acute ischemic stroke. It has been suggested that thrombus length would influence functional outcome via interaction with the collateral circulation. We investigated the individual and combined effects of thrombus length assessed by the clot burden score and collateral status assessed by a FLAIR vascular hyperintensity-ASPECTS rating system on functional outcome (mRS).

Materials and methods: Patients with anterior circulation acute ischemic stroke due to large-vessel occlusion from the ASTER and THRACE trials treated with endovascular thrombectomy were pooled. The clot burden score and FLAIR vascular hyperintensity score were determined on MR imaging obtained before endovascular thrombectomy. Favorable outcome was defined as an mRS score of 0-2 at 90 days. Association of the clot burden score and the FLAIR vascular hyperintensity score with favorable outcome (individual effect and interaction) was examined using logistic regression models.

Results: Of the 326 patients treated by endovascular thrombectomy with both the clot burden score and FLAIR vascular hyperintensity assessment, favorable outcome was observed in 165 (51%). The rate of favorable outcome increased with clot burden score (smaller clots) and FLAIR vascular hyperintensity (better collaterals) values. The association between clot burden score and functional outcome was significantly modified by the FLAIR vascular hyperintensity score, and this association was stronger in patients with good collaterals, with an adjusted OR = 6.15 (95% CI, 1.03-36.81).

Conclusions: The association between the clot burden score and functional outcome varied for different collateral scores. The FLAIR vascular hyperintensity score might be a valuable prognostic factor, especially when contrast-based vascular imaging is not available.

Trial registration: ClinicalTrials.gov NCT02523261 NCT01062698.

© 2021 by American Journal of Neuroradiology.

Figures

FIG 1.

Shape of association of favorable outcome with the CBS (A) and FVH score (B). Curves were obtained by fitting a generalized additive model (binomial distribution with a logit link function) with a cubic smoothing spline term.

FIG 2.

Association of favorable outcome and a high CBS according to the FVH Score. 1Sensitivity analysis was performed in all patients with MR imaging (n = 416) after handling missing values by multiple imputation. 2Prespecified adjustment on the study (ASTER versus THRACE), age, sex, admission NIHSS, intravenous tPA, and onset-to-groin puncture time. P het indicates an interaction test between the clot burden score and the FVH grade (treated as a 6-level ordinal variable).