Low Blood Flow in Back of Brain Increases Risk of Recurrent Stroke

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Patients who have had a stroke in the back of the brain are at greater risk of having another within 2 years if blood flow to the region is diminished, according to a study published in JAMA Neurology.
These patients are the most likely to benefit from risky intervention to unblock arteries, and they can be identified using a new magnetic resonance imaging (MRI)-based technology developed at the University of Illinois at Chicago, Chicago, Illinois.
“Having a blockage present in a blood vessel doesn’t always correlate to low blood flow,” said principal investigator Sepideh Amin-Hanjani, MD, University of Illinois at Chicago College of Medicine. “There can be a blockage and flow can be normal, if other nearby blood vessels are able to compensate.”
The researchers wanted to try to identify which patients who had experienced a stroke were at highest risk for further strokes and so might benefit from angioplasty despite the risks of the procedure.
They followed 72 adult patients who had a stroke or a transient ischemic attack (TIA) in the back of the brain and who also had at least 50% blockage of the arteries in that part of the brain. The patients were followed for an average of 22 months at 5 academic medical centres as they continued receiving standard care for their condition from their neurologists.
Patients were evaluated for reduced blood flow in the back of the brain using Non-Invasive Optimal Vessel Analysis (NOVA), a software program that can quantify the volume, velocity, and direction of blood flowing through any major vessel in the brain using standard MRI equipment.
One-fourth of the patients were found to have diminished blood flow in the back of the brain, which turned out to be a significant predictor of subsequent stroke. These patients had 12- and 24-month stroke-free survival rates of 78% and 70%, respectively, compared to 96 percent and 87 percent for patients with normal blood flow.
“At 1 year, the risk for patients with low blood flow was about 5 times as high as risk for patients without low flow in the back of the brain,” said Dr. Hanjani.
For these patients, the benefits of angioplasty probably outweigh the risks.
“About three-quarters of patients didn't have low blood flow in the vertebrobasilar region and these patients would not benefit from treatments aimed at opening the vessels, such as angioplasty,” said Dr. Hanjani. “In fact, the procedure would put these patients at unnecessary risk.”
The ultimate goal is to find what treatments might be most effective for each patient, he added.
The researchers hope that the ease of identifying the high-risk group using NOVA will enable further study of the condition and the evaluation of new therapies to further reduce the risk of recurrent stroke.
SOURCE: University of Illinois at Chicago