In a recent study published by JAMA Neurology, a team of researchers analyzed how imaging techniques could inform decisions on whether to transfer stroke patients to centers capable of blood clot removal.

They found clinical severity of stroke and poor collateral circulation were most strongly associated with decaying Alberta Stroke Program Early CT Score (ASPECTS) upon arrival to a comprehensive stroke center. Poor or no leptomeningeal collateral blood flow—measured by CT angiography (CTA)—was associated with a 5.14-fold increased risk of ASPECTS worsening from six or higher to less than six, making the patient less likely to benefit from thrombectomy according to clinical guidelines.

Of the 316 patients included in the retrospective, single-center study, 19.6 percent experienced ASPECTS reduction across that threshold. That percentage increased to 89 percent for patients who showed poor collateral blood flow at the second center a median of 3.2 hours after presentation at the initial hospital.

The analysis included patients transferred from one of 30 referring hospitals to a thrombectomy-capable stroke center (TCSC). Individuals were tested via CT at the referring hospital and CTA at the destination center—suggesting earlier CTA may be necessary to provide a better risk assessment.

“In a stroke network setting, vascular imaging to identify intracranial occlusions and assess collateral blood vessels may provide an additional tool for determining triage decisions when transferring a patient to a TCSC,” wrote lead researcher Gregoire Boulouis, MD, with Massachusetts General Hospital and Harvard Medical Center, and colleagues.

“These decisions include the mode of transportation (air for patients at greatest risk of rapid ASPECTS decay), the most appropriate destination center, and the utility of transfer at all (for patients unlikely to have adequate viable tissue volume by the time they reach the destination center). … Our findings therefore support the use of CTA for selected patients at the acute phase of ischemic stroke in (referring hospitals) and community hospitals.”

The authors noted implementing these imaging techniques in patient triage would need to be tailored to each region’s resources and needs.

In an accompanying editorial, Bruce Campbell, MBBS, PhD, said it is important CTA occur immediately after noncontrast CT.

“The new era of thrombectomy in an extended time window is particularly relevant to regional centers with long transfer times, and eligibility is critically dependent on collateral imaging,” he wrote. “It makes clinical and economic sense to identify these patients at initial assessment rather than indiscriminately transferring patients who have no chance of proceeding to thrombectomy.”