Effects of Collateral Status on Infarct Distribution Following Endovascular Therapy in Large Vessel Occlusion Stroke

It is unknown whether collateral vessel status, as seen on computed tomography angiography, can predict the fate of penumbral tissue identified on perfusion computed tomography and thereby influence clinical outcome. We tested this hypothesis in consecutive patients who underwent perfusion computed tomography/computed tomography angiography within 6 h of anterior circulation stroke, who also had repeat perfusion/infarct volume imaging at 24 h, and modified Rankin Scale at 3 months. Collateral status was graded as good or reduced depending on the extent of contrast visualized distal to the occlusion on computed tomography angiography. 'Perfusion computed tomography mismatch' ratio was calculated from the ratio of the mean transit time lesion/cerebral blood volume lesion. Of 92 patients with proximal intracranial vessel occlusion, good collateral status (51/92) was significantly associated with reduced infarct expansion and more favourable functional outcomes (modified Rankin Scale 0-2). Significant univariate predictors of favourable outcome were good collateral status, major reperfusion at 24 h, presence of perfusion computed tomography mismatch (for a range of ratios: > or = 1.2, > or = 2, > or = 3, > or = 3.5) and baseline National Institutes of Health Stroke Scale score. Notably, none of the 37 patients with a perfusion computed tomography mismatch ratio < 3.0 had a favourable outcome. In patients with perfusion computed tomography mismatch, significant independent predictors of favourable outcome were good collateral status, major reperfusion and baseline National Institutes of Health Stroke Scale score. There was also a strong interaction between major reperfusion and good collateral status in the regression models. In patients with proximal vessel occlusion, perfusion computed tomography mismatch is a prerequisite for a favourable clinical response, but good collateral status appears a critical determinant of ultimate outcome, particularly if major reperfusion occurs.

Despite the abundance of emerging multimodal imaging techniques in the field of stroke, there is a paucity of data demonstrating a strong correlation between imaging findings and clinical outcome. This study explored how proximal arterial occlusions alter flow in collateral vessels and whether occlusion or extent of collaterals correlates with prehospital symptoms of fluctuation and worsening since onset or predict in-hospital worsening. Among 741 patients enrolled in a prospective cohort study involving CT angiographic imaging in acute stroke, 134 cases with proximal middle cerebral artery occlusion and 235 control subjects with no occlusions were identified. CT angiography was used to identify occlusions and grade the extent of collateral vessels in the sylvian fissure and leptomeningeal convexity. History of symptom fluctuation or progressive worsening was obtained on admission. Prehospital symptoms were unrelated to occlusion or collateral status. In cases, 37.5% imaged within 1 hour were found to have diminished collaterals versus 12.1% imaged at 12 to 24 hours (P=0.047). No difference in worsening was seen between cases and control subjects with adequate collaterals, but cases with diminished sylvian and leptomeningeal collaterals experienced greater risk of worsening compared with control subjects measured either by admission to discharge National Institutes of Health Stroke Scale increase > or =1 (55.6% versus 16.6%, P=0.001) or > or =4 (44.4% versus 6.4%, P<0.001). Most patients with proximal middle cerebral artery occlusion rapidly recruit sufficient collaterals and follow a clinical course similar to patients with no occlusions, but a subset with diminished collaterals is at high risk for worsening.

Recent randomized trials have proven the benefit of intra-arterial treatment (IAT) with retrievable stents in acute ischemic stroke. Patients with poor or absent collaterals (preexistent anastomoses to maintain blood flow in case of a primary vessel occlusion) may gain less clinical benefit from IAT. In this post hoc analysis, we aimed to assess whether the effect of IAT was modified by collateral status on baseline computed tomographic angiography in the Multicenter Randomized Clinical Trial of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands (MR CLEAN).