Impact of collateral status on functional outcomes in acute cardioembolic stroke after successful endovascular thrombectomy

Background Collateral circulation sustains the ischemic penumbra during acute large vessel occlusion (LVO). However, its prognostic significance in cardioembolic stroke (CS) patients following successful endovascular thrombectomy (EVT) remains unclear. We investigated whether collateral status influences functional outcomes in acute CS patients achieving successful recanalization [modified Thrombolysis in Cerebral Infarction (mTICI) grade ≥2b]. Methods We retrospectively analyzed consecutive CS patients achieving successful recanalization with EVT. Collateral status was assessed using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) grading system on digital subtraction angiography (DSA). The primary outcome was functional independence [modified Rankin Scale (mRS) 0–2] at 3 months. Secondary outcomes included excellent outcome (mRS 0–1) at 3 months, in-hospital and 3-month mortality, and PH (parenchymal hematoma type 1c or 2) within 72 h. Multivariable logistic regression and subgroup analyses were performed to identify independent associations. Results Among 354 patients, 211 (59.6%) had good collaterals (ASITN/SIR 2–4) and 143 (40.4%) had poor collaterals (ASITN/SIR 0–1). After adjustment for confounders, good collateral status independently predicted functional independence [adjusted odds ratio (aOR), 2.07; 95% CI, 1.13–3.83; p = 0.020], with rates of 61.6% versus 37.1% in the good versus poor collateral groups. Good collaterals were also independently associated with excellent outcome (aOR, 1.89; 95% CI, 1.03–3.50; p = 0.042), lower in-hospital mortality (aOR, 0.24; 95% CI, 0.08–0.63; p = 0.006), lower 3-month mortality (aOR, 0.39; 95% CI, 0.18–0.78; p = 0.009), and reduced PH rates within 72 h (aOR, 0.51; 95% CI, 0.27–0.93; p = 0.029). The association between collateral status and functional independence was modified by baseline Alberta Stroke Program Early CT Score (ASPECTS) ( P for interaction = 0.007). Conclusion In CS patients achieving successful recanalization, good collateral status is independently associated with improved functional independence and excellent outcome, reduced PH rates within 72 h, and lower in-hospital mortality and 3-month mortality. Collateral assessment may enhance prognostic stratification, particularly in patients with lower baseline ASPECTS.