Perfusion Imaging Key to Identifying Thrombectomy Candidates

Stroke is the second leading cause of death around the world, and a leading cause of disability. For patients who have experienced a large core stroke, tissue plasminogen activator (tPA), a clot-dissolving drug that has long been the mainstay of treatment, may not work effectively, if at all. Select patients with large core strokes are candidates for mechanical thrombectomy (MT), which uses tiny wire cages called stent retrievers to remove large clots from a blocked artery in the brain;1 it has been shown to be safe and effective for those patients who have minimal damaged brain tissue.2 Despite this, patients who present with large ischemic core strokes are routinely excluded from thrombectomy treatment “due to the lack of clinical evidence and concerns for procedural safety, futility, and cost-effectiveness,” write the authors of a study published in Endovascular Today.3

Patients with large core stroke benefit from mechanical thrombectomy

Late-breaking research presented at the American Stroke Association’s International Stroke Conference in February 2019 and published in JAMA Neurology in July 2019, now suggests that mechanical clot removal for some patients with large core strokes may yield good outcomes. The study looked at 2,453 patients who were treated with mechanical clot removal, of which 221 had large core strokes. Thirty-five percent of those patients achieved functional independence at the three-month mark, which is considered a good outcome.4

In the study, longer time lapses between stroke and treatment were associated with poorer outcomes and increased complications such as brain bleeds and death. In particular, after 12 hours of stroke onset, there was a much lower likelihood that mechanical clot removal would result in a good outcome.4

Outcomes were also tied to the size of the stroke—the larger the stroke, the worse the outcome. For patients with strokes over 100 mL in volume, brain bleed occurred in up to 75 percent of patients and deaths in up to 50 percent. For those with strokes under 100 mL volume, four percent experienced brain bleeds and 12 percent died.4

This study used computed tomography (CT) imaging as well as perfusion imaging, an advanced imaging technique with contrast. The authors found that perfusion imaging may help identify those patients who are most likely to benefit from the mechanical thrombectomy procedure. The upcoming SELECT2 trial will build on the results of this study and will utilize perfusion imaging to select the best candidates for mechanical clot removal.2

CT perfusion imaging uses sequential brain imaging to evaluate the flow of contrast dye through the brain’s blood vessels, as well as total cerebral blood volume and the extent of cerebral blood flow to specific brain regions. This information allows the physician to estimate the extent of both reversible and irreversible ischemic tissue, according to a study in Clinical Medicine (London).5

New trial to use perfusion imaging to identify best candidates for thrombectomy

SELECT2 (Optimizing Patient Selection for Endovascular Treatment in Acute Ischemic Stroke) is an international, multicenter Phase III clinical trial that began enrolling in August 2019 and will enroll 560 patients at 30 comprehensive stroke centers in the United States, Canada, and Europe. It is designed to assess the potential safety and benefits of mechanical thrombectomy for larger strokes. This and other future randomized trials will help confirm this study’s result and identify which criteria are best to use when evaluating patients for mechanical thrombectomy.

Dr. Amrou Sarraj, the first author on the study and associate professor of neurology at McGovern Medical School at the University of Texas Health Science Center at Houston said, “If proven to be safe and effective, SELECT2 will extend thrombectomy indications to improve clinical outcomes in a large group of patients that does not have many treatment options at this point,” in a news story about the upcoming trial.6


1. Guidelines Urge New Approach to Treating Worst Strokes. American Heart Association News. Last accessed September 25, 2019.

2. Size and Time Impact Outcomes When Mechanical Clot Removal Used for Large Core Strokes. American Heart Association News. Last accessed September 25, 2019.

3. What We Know and What We Don’t: Mechanical Thrombectomy for Large Core Strokes. Endovascular Today. Last accessed September 25, 2019.

4. Outcomes of Endovascular Thrombectomy vs Medical Management Alone in Patients With Large Ischemic Cores. JAMA Neurology. DOI: 10.1001/jamaneurol.2019.2109 Last accessed September 25, 2019.

5. What Is New in Stroke Imaging and Intervention? Clinical Medicine (London). Last accessed September 25, 2019.

6. Clinical Trial Reveals Potential for Treating Larger Strokes With Thrombectomy. University of Texas Health Science Center at Houston. Last accessed September 25, 2019.