Objective To identify angiographic predictors impacting clinical outcome in patients undergoing endovascular therapy for acute ischemic stroke (AIS).

Methodology A retrospective analysis was performed on patients undergoing endovascular therapy for AIS secondary to arterial occlusion in the anterior circulation over a consecutive 30 month period. The site of vascular occlusion was divided into three groups: Group1-ICA: intracranial internal carotid artery occlusion with or without extension into any of the terminal branches; group2-MCA: middle cerebral artery occlusion either at the main stem or the MCA bifurcation with thrombus extending into the proximal M2 branches; and group3-M2/M3: isolated M2 branch occlusion without involvement of the MCA bifurcation or those with an M3 occlusion. Collateral blood supply was graded on the pre-intervention angiogram based on pial collaterals. For MCA occlusions, anterior cerebral artery (ACA) collaterals from an ipsilateral carotid injection were assessed, and for ICA terminus occlusion, the ACA collateralization was determined from a contralateral carotid injection. The pial collaterals were graded as: no collaterals (grade 0), some collaterals with retrograde opacification of the distal MCA territory (grade 1) and good collaterals, with filling of the proximal MCA (M2) branches or retrograde opacification up to the occlusion site (grade 2). Angiographic recanalization was based on the TIMI grading system (successful recanalization: TIMI 2–3) and clinical outcome on the modified Rankin score (mRS) at 3–6 months of follow-up. All patients had been selected for treatment based on their preprocedure CT angiogram and perfusion imaging.

Results 98 patients with anterior circulation AIS who had undergone endovascular therapy (lytics and/or mechanical therapy) were studied. Of these, a clinical follow-up and mRS were obtained on 86 patients. Procedural factors (such as recanalization, time to procedure, location of occlusion) were analyzed for all 98 patients but only the 86 patients with a clinical outcome were studied for factors impacting outcome. Overall, a good outcome (mRS 0–2) was seen in 47.6% of the patients. Successful recanalization (TIMI 2–3) was achieved in 56% of patients. Predictors of good outcome were divided into pre- and intraprocedural factors. Among the preprocedure factors, logistic regression analysis showed that a higher age (p=0.004) and National Institutes of Health Stroke Scale (NIHSS) (p=0.0009) at admission were the most significant predictors of a poor outcome. Intraprocedural factors such as site of occlusion (p=0.001), degree of recanalization (p<0.0001), extent of collaterals (p=0.001) and procedure duration (p=0.003) were significantly associated with the clinical outcome. Distal occlusions, successful recanalization and shorter procedures were associated with good outcome. A good collateral grade was an independent predictor of good clinical outcome. However, the time to procedure from symptom onset was not significantly associated with the clinical outcome.

Conclusion Angiographic factors such as the degree of recanalization have been previously shown to be predictors of outcome. We demonstrate that the collateral blood supply plays an important role in independently determining clinical outcome. This is important as preprocedure perfusion imaging and calculation of viable brain may be related to the state of the collateral circulation thus aiding in patient selection and predicting outcome. Separate studies need to be done to confirm this hypothesis.