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Wednesday, September 27, 2017

Imaging Factors Identified for Infarct Progression in Stroke Patients Undergoing Thrombectomy

BY SARAH OWENS

Baseline clinical imaging factors, including poor collateral blood flow and clinical stroke severity, are associated with infarct progression, which could make stroke patients ineligible for thrombectomy, according to a new study published online on September 25 in JAMA Neurology.

Patients with stroke who undergo imaging at a referral hospital often show a favorable profile for thrombectomy, including an Alberta Stroke Program Early CT [computed tomography] Score (ASPECTS) of at least 6. However, on the way to a thrombectomy-capable hospital, their infarcts often worsen, and by the time they arrive, they may no longer be eligible for the clot-removal procedure. Predicting which patients will become ineligible during transfer may help reduce unnecessary transfers.

In certain subgroups of patients with ischemic stroke, vascular imaging at the referring hospitals may play a critical role in determining the benefits of transfer for thrombectomy, wrote the study authors led by Gregoire Boulouis, MD, MSc, of the department of neuroradiology at Université Paris-Descartes in Paris, France, and colleagues.

For the study, researchers retrospectively analyzed data that was collected prospectively on 316 adult patients with stroke who transferred from one of 30 RHs to a single TCSC in a single regional stroke network between January 1, 2010 and January 1, 2016. The patients averaged 70 years in age, and 56.6 percent were male. All patients had undergone CT scans at the referring hospitals and CT angiography at the thrombectomy-capable stroke center. They scored at least 6 on the 10-point ASPECTS score, a CT-based measure of stroke severity, with lower scores indicating greater severity.

Based on the CTs taken at the referral hospital and the stroke center for thrombectomy, the researchers analyzed the ASPECTS scores, presence and localization of a dense vessel sign, presence and localization of a vessel occlusion on CT angiography, degree of leptomeningeal collateral blood flow, and presence and classification of interval hemorrhagic transformation per the European Cooperative Acute Stroke Study criteria. They established a critical ASPECTS score of 6, below which patients were deemed unlikely to gain clinical benefit; their main outcome was a decline in the ASPECTS score from 6 or higher to less than 6 during transfer.

Among the clinical imaging factors strongly associated with ASPECTS decline were higher National Institutes of Health Stroke Scores, lower baseline ASPECTS scores, and no or poor collateral blood vessel status. Of these, collateral blood vessel status had the highest adjusted odds ratio of 5.14 (95%CI, 2.20-12.70; p<0.001). The results were similar when the researchers extended the sample of patients with ASPECTS decay to include patients who had initially unfavorable imaging profiles.

In an accompanying editorial, Bruce C. V. Campbell, MBBS(Hons), BMedSc, PhD, FRACP, head of hyperacute stroke in the department of neurology at the Royal Melbourne Hospital in Melbourne, Australia, praised the  study, noting that the importance of cerebral blood flow means "the success of extended window trials [for thrombectomy] should not distract from the 'time is brain' imperative to achieve reperfusion as fast as possible in each patient."

The researchers noted several limitations to their study. Among them, the study was conducted at a single academic center, which may limit the generalizability of the findings; and imaging readings were done in an optimal research environment, rather than in a realistic acute care setting, although the study showed good interrater agreement.

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