A peer-reviewed study published in Radiology this month concludes that computed tomography angiography (CTA) may be used to identify stroke victims who may still benefit from an endovascular thrombectomy even after 24 hours have passed since the initial blockage.

A large vessel occlusion stroke occurs when a blood clot becomes lodged in one of the large arteries resulting in interruption of the flow of blood to the brain. Such strokes are typically the most serious, and make up the largest share of stroke-related deaths and long-term disability.

Endovascular thrombectomy is a treatment in which a tube is inserted into the affected artery and used to neutralize the blockage, allowing the normal flow of oxygenated blood to the brain to resume. Albeit extremely effective at reducing the incidence of death and severe long term disability in stroke victims, until somewhat recently it was only considered effective if administered very soon after the initial onset, preferably within six to eight hours.
A study published in 2017 found that patients who had the benefit of a thrombectomy had significantly better outcomes after 90 days compared to patients who were only treated with medication.

Building on prior research published in Scientific Reports, that identified a significant class of stroke victims that may benefit from a thrombectomy up to and beyond 24 hours since the initial blockage, Dr. Gilberto Gonzalez, along with co-author Dr. Robert Regenhardt, reviewed imaging and reports of 31 stroke patients in order to determine how such patients may be more easily identified.

“Thrombectomy is over 90% effective if we get to the patient in time,” stated Gonzalez, “The problem is, we’re only treating less than 10% of the people who might benefit.”

The authors’ research revealed that nearly half of stroke patients may have sufficiently slow growing ischemic cores, i.e., growth in the severity of the arterial blockage, such that that they may remain good candidates for a thrombectomy up to and beyond 24 hours since the initial interruption of blood flow.

“Our data shows that in almost half of patients, the core grows very slowly ... That’s a huge number of people who are potentially treatable,” stated Dr. Gonzalez.

More importantly, they found that the rate of ischemic core growth correlates strongly with the rate of flow through collateral blood vessels, as the body attempts to compensate for the arterial blockage by delivering more oxygenated blood to the brain via alternative routes.

Although prior research has determined that both simple and complex imaging can be effective at determining whether a stroke patient is a good candidate for a thrombectomy, these new findings indicate that such patients may be able to be identified by CTA alone.

According to the study’s authors, CTA is widely available in most hospitals, and with these new findings and additional research, could be used for early identification of prospective thrombectomy patients in hospitals that otherwise lack CT perfusion and MR imaging systems.

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