Impact of cerebral venous outflow on futile recanalization despite complete reperfusion following mechanical thrombectomy

Background A substantial proportion of patients with acute ischemic stroke remain functionally dependent despite complete angiographic reperfusion (modified Thrombolysis in Cerebral Infarction [mTICI] 3) after mechanical thrombectomy (MT). This mismatch, commonly termed futile recanalization, may reflect tissue-level hypoperfusion not captured by arterial reperfusion grading. We investigated whether cerebral venous outflow, assessed using the Cortical Vein Opacification Score (COVES), provides prognostic information beyond conventional clinical and arterial imaging variables.Methods We retrospectively analyzed 420 adults with anterior-circulation large-vessel occlusion who underwent MT between 2015–2025 and achieved mTICI 3 reperfusion. Venous outflow was graded on baseline computed tomography angiography using COVES. Futile recanalization was defined as a 90-day modified Rankin Scale score of 3–6. Independent associations with futile recanalization were evaluated using multivariable binary logistic regression.Results Futile recanalization occurred in 191 patients (45.5%). After adjustment for age, admission NIHSS, ASPECTS, total passes, hypertension, diabetes mellitus, previous stroke, and arterial collateral status, higher COVES remained independently associated with lower odds of futile recanalization (OR per 1-point increase, 0.649; 95% CI, 0.537–0.784; p < 0.001). Age (OR, 1.031; p = 0.005), admission NIHSS (OR, 1.091; p = 0.001), and total passes (OR, 1.538; p < 0.001) were independently associated with higher odds of futile recanalization. Arterial collateral status was not independently associated with outcome. COVES showed greater discrimination than admission NIHSS (AUC, 0.742 vs 0.624).Conclusions Baseline COVES was independently associated with 90-day functional outcome among patients achieving complete reperfusion after MT. COVES may serve as a complementary prognostic imaging marker rather than a treatment-selection tool. Prospective external validation is required.