Post-Endovascular Thrombectomy Perfusion Imaging (CT and MR) as a Prognostic Biomarker and Patient-Selection Tool for Adjuvant Therapy: A Systematic Review, Meta-Analysis, and Clinical Threshold Framework.
TL;DR
Post-EVT perfusion imaging (CT or MR) provides tissue-level reperfusion information that complements modified Thrombolysis in Cerebral Infarction (mTICI) grading and identifies biologically distinct patient subgroups.
Abstract
Background
AND
Purpose
Despite high rates of macrovascular recanalization, approximately half of patients with large vessel occlusion stroke fail to achieve functional independence after endovascular thrombectomy (EVT). Residual tissue-level perfusion abnormalities - detectable on post-procedural CT perfusion (CTP) - have been proposed as a biomarker of futile recanalization. We aimed to establish post-EVT perfusion imaging (by CT or MR perfusion) as a surrogate marker predictive of functional independence on the modified Rankin Scale - by synthesizing evidence-based perfusion thresholds and defining the optimal acquisition timing. Analysis was restricted to studies performing perfusion imaging exclusively after EVT, so that thresholds reflect post-procedural reperfusion status rather than pre-treatment ischemic burden.
Methods
We systematically searched MEDLINE, EMBASE, and the Cochrane Library from January 2018 through April 2026 for cohort studies performing perfusion imaging after EVT, reporting at least one quantitative CT- or MR-perfusion parameter alongside functional outcome (modified Rankin Scale [mRS] at any post-procedural time point) or neurological outcome (National Institutes of Health Stroke Scale [NIHSS]), and enrolling ≥10 patients. Both anterior and posterior circulation occlusions were eligible. The review was conducted in accordance with PRISMA 2020 (checklist provided as supplementary material). Risk of bias was assessed using the ROBINS-I tool. Pooled odds ratios (ORs) were estimated using the DerSimonian-Laird random-effects estimator. A pre-specified sensitivity analysis excluded our proof-of-concept cohort (which received adjunctive cerebrolysin) to isolate the pooled estimate from any treatment-related influence.
Results
Eight independent post-EVT perfusion imaging studies (670 patients; five CT-perfusion, two MR-perfusion, and one mixed CT/MR cohort) met inclusion criteria. Residual hypoperfusion was present in 21-53% of angiographically successful reperfusions and was consistently associated with reduced odds of functional independence (pooled OR 0.28, 95% CI 0.15-0.51; I²=6%). The pre-specified sensitivity analysis excluding the cerebrolysin-treated cohort yielded a pooled OR of 0.30 (95% CI 0.16-0.54; I²=0%), confirming that the pooled effect is not driven by the adjuvant-treated subgroup. A Tmax >6 s volume <3.5 mL at 30-90 minutes post-EVT was the most consistently validated CT-perfusion threshold (adjusted OR 3.5, 95% CI 1.6-7.8); for MR perfusion, an rCBV-defined impaired-microvascular-reperfusion volume >5 mL was the corresponding threshold. The optimal perfusion acquisition window is 30-120 minutes post-EVT.
Conclusions
Post-EVT perfusion imaging (CT or MR) provides tissue-level reperfusion information that complements modified Thrombolysis in Cerebral Infarction (mTICI) grading and identifies biologically distinct patient subgroups. Standardized post-EVT perfusion imaging at 30-120 minutes, applied with the proposed threshold framework, should be considered as an eligibility criterion and stratification variable in future trials of post-EVT adjuvant therapy across the pharmacological spectrum.