Despite recent endovascular trials demonstrating improved outcomes, rate of functional dependence or death at 3 months following anterior circulation infarct secondary to proximal occlusion remains high. Clinical factors predicting clinical outcome include age, baseline stroke scale, and blood pressure. A radiological factor that has been shown to positively correlate with clinical outcome is collateral status. While digital subtraction angiography is considered the gold standard, this method is unfeasible in the acute setting. A non-invasive modality is dynamic-CTA which provides time-resolved images of arterial, parenchymal, and venous phases. In this study, the authors investigated the value of collateral status in predicting clinical outcomes.
Patients were retrospectively selected from the Dutch Acute Stroke Trial (DUST) and the Multicenter Randomized Clinical trial of Endovascular treatment for Acute ischemic stroke in the Netherlands (MR CLEAN). In total, 70 patients with proximal middle cerebral artery occlusion were selected in whom dynamic CTA was obtained. CTA was scored on a 0-3 scale, 3 corresponding to complete collateral filling of the occluded territory. Speed of collateral filling was also measured and dichotomized to fast versus slow filling based on filling of the asymptomatic hemisphere.
Of the 70 patients, only 17 patients underwent endovascular treatment. At 3 months, 60 patients had either dead or had poor clinical outcome, as defined as a modified rankin score of greater than three. Poor clinical outcome was strongly related to poor arterial filling on dynamic CTA. Risk of poor outcome decreased with increasing collateral score. Speed of filling did not have a strong correlation to clinical outcome.
This study suggests that dynamic CTA can reliably assess collateral status and that collateral status is positively correlated with clinical outcome. This study, however, was limited by relatively low number of patients. Furthermore, this study was not powered to assess affect of collateral status on treatment types. Therefore, conclusions regarding patient selection for acute treatment would be premature. Further studies are needed to determine clinical utility of obtaining collateral status in the acute setting. For example, a patient with a proximal anterior circulation occlusion with poor collaterals who presents within the appropriate time frame should still be offered endovascular therapy. One potential utility of obtaining collateral status, as supported by this study, could be to aid in prognostication for patients and families.
