Introduction Randomized trials have established endovascular thrombectomy (EVT) as an effective treatment for reducing disability in large ischemic strokes, yet the impact of arterial collateral status remains uncertain.

Aim of Study The study aimed to explore whether the status of arterial collaterals alters the efficacy of EVT in patients experiencing large ischemic strokes.

Methods The TENSION trial, a multicenter randomized clinical trial, enrolled patients with acute large ischemic strokes due to anterior circulation large vessel occlusion. Participants were randomized to receive either EVT along with medical treatment or medical treatment alone within 12 hours of stroke onset. Collateral status was assessed using the Tan score on baseline CT angiography and categorized as either poor (grade 0-1) or good (grade 2-3). The primary outcome was the shift on the modified Rankin Scale score at 90 days.

Results Out of 201 patients, 51% received EVT and 49% received medical treatment alone. EVT was highly effective in patients with good collaterals (acOR, 3.93, 95% CI, 1.65-9.69, P=.002) and in patients with poor collaterals (acOR, 3.92, 95% CI, 2.12-6.54, P<.001), without modification of treatment effect by collateral status (interaction term, p=0.88). Furthermore, there was no significant influence of collateral status in dependance of time to treatment or mode of transportation.

Conclusion The findings from the TENSION trial demonstrate that EVT significantly decreases functional disability in patients with large ischemic strokes irrespective of their arterial collaterals. Therefore, EVT should be considered for all eligible patients within 12 hours from symptom onset, regardless of collateral circulation quality.