Low Blood Flow May Increase Recurrent Stroke Risk

Patients who have low blood flow to the back of the brain are at higher risk for recurrent stroke, according to the results of a 6-year, multi-center trial presented earlier this month at the International Stroke Conference in Nashville, Tenn.

In addition, these high-risk patients can easily be identified using specialized software developed at the University of Illinois at Chicago (UIC) that analyzes blood flow using standard MRI technology.
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“Evaluation of blood flow in the vertebrobasilar system can distinguish those patients with symptomatic vertebrobasilar stenosis who are at very high vs. low risk of subsequent new strokes, despite medical therapies,” says principal investigator Sepideh Amin-Hanjani, MD, professor of neurological surgery at the UIC College of Medicine.

Patients with vertebrobasilar disease (VBD) have a blockage of the blood vessels that supply blood to the back of the brain. Blood flow varies according to how severe the patient’s blockage is—some patients have normal blood flow while others have blockages ranging from partial to complete.

Sponsored by the National Institutes of Health, the Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) Trial set out to determine if patients with VBD and low blood flow had a higher risk of recurrent stroke than those with normal posterior blood flow.

All together, 73 adult stroke patients—with a mean age of 66—were enrolled at 5 study sites across North America. Investigators assessed them for low posterior blood flow and followed them for an average of 22 months. For the duration of the study, all patients continued under the care of their neurologists and received standard care for their condition.

All of the study subjects had symptomatic VBD—one quarter of them were identified as having low posterior blood flow. AS the trial progressed, low blood flow emerged as an independent risk factor for recurrent stroke.

Within the first 12 months, patients with low blood flow had a 22% risk of recurrent stroke compared to just 4% in patients with normal blood flow.  At 24 months, the risk for patients with low blood flow rose to 30% vs. 13% for other patients.

Hanjani says the risk of recurrent stroke associated with VBD may be tied to several factors.

 “The primary theory would be that low blood flow creates a hemodynamically high-risk environment, which can lead to a critical lack of blood flow to an area of the brain resulting in stroke,” she explains.

The technique, based on widely available technology, could help health care providers to better determine the best course of treatment for each patient with VBD.

“The VBD patients at highest risk of recurrent stroke can be identified by undergoing the simple noninvasive quantitative MRA test—NOVA—that measures blood flow,” Hanjani says. “Those high-risk patients could be targeted for more aggressive medical therapies or ultimately, with further study, to interventions that could treat their vessel stenosis directly, such as surgical or endovascular interventions.”

On the other hand, those identified as having adequate blood flow wouldn’t need to incur the risk of undergoing additional procedures.

Hanjani and her colleagues have continued plans for research in this area. “We are interested in evaluating the interventions that may reduce the risk of stroke in these high-risk patients,” she says.

—Colleen Mullarkey

Reference

Amin-Hanjani S, Pandey DK, Rose-Finnell L, Du X, Richardson D, Thulborn KR, et al. Impact of hemodynamics on stroke risk in symptomatic vertebrobasilar disease:

results of the VERiTAS Study. Presented at: International Stroke Conference, Nashville, Tenn. Feb. 12, 2015. 15-ISC-LB-5214-AHA.