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Vertebrobasilar disease, low distal flow triggers strokes

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VERiTAS shows distal flow matters

The main message from VERiTAS is that low blood flow distal to vertebrobasilar arterial stenosis matters. When a patient with a posterior-circulation stroke has an occlusion or high-grade stenosis causing poor distal flow they have an increased risk for recurrent stroke.

Mitchel L. Zoler/Frontline Medical News

Dr. Colin P. Derdeyn

The VERiTAS results move the field forward by providing another brick in the wall of evidence that reduced perfusion in patients with occlusive cerebrovascular disease identifies a group of patients who are at high risk for a future stroke. I believe that this sort of disease is fairly common, but clinicians often do not actively look for it because no treatment for it has been proven effective. Recent trial results failed to show benefit from either angioplasty or stenting.

The next step will be a trial focused on with low-flow patients that treats them with more aggressive medical management or with an intervention to try to identify some treatment that produces incremental benefit in this target population.

Until we see positive results in such a trial, the practical implications of the VERiTAS results are unclear. VERiTAS provides a good indication of the natural history of vertebrobasilar disease when patients receive today’s standard treatment. Patients with low distal flow had about a 20% rate of new strokes during 12 months of follow-up; outcomes were much better among patients with normal distal flow.

Some clinicians will see the high risk among low-flow patients as justification for some sort of intervention even though nothing has been proven to work. Others will take a more conservative approach and treat these patients with standard medical treatment for atherosclerotic disease, or enroll them into an intervention trial. Arguably, there is no reason to even measure distal flow on a routine basis right now because there is no proven way to act on this information.

The method used in VERiTAS to noninvasively measure distal flow – quantitative MR angiography with the NOVA software – is probably not widely used today, but the VERiTAS results might change that. The study’s findings show that this type of imaging can produce clinically meaningful measurements; not many other imaging technologies can say that as of now.

Dr. Colin P. Derdeyn is professor of neurology and director of the Center for Stroke and Cerebrovascular Disease at Washington University in St. Louis. He was a coinvestigator on VERiTAS. He has received research support from MicroVention and has a modest ownership interest in Pulse Therapeutics. He made these comments in an interview.


 

AT THE INTERNATIONAL STROKE CONFERENCE

References

NASHVILLE, TENN. – In patients with symptomatic vertebrobasilar disease, low distal flow measured noninvasively predicted a patient’s subsequent risk for stroke in a multicenter, prospective study of 72 patients.

The finding “has implications for investigating interventional or aggressive medical treatments,” which should be aimed at this high-risk subgroup of patients, Dr. Sepideh Amin-Hanjani said at the International Stroke Conference, sponsored by the American Heart Association.

Dr. Sepideh Amin-Hanjani Mitchel L. Zoler/Frontline Medical News

Dr. Sepideh Amin-Hanjani

Patients with “the highest risk for recurrence have the best chance to benefit from intervention,” said Dr. Amin-Hanjani, professor of neurosurgery and codirector of neurovascular surgery at the University of Illinois at Chicago. For the time being, no interventions for vertebrobasilar disease have proven efficacy and safety, but the new finding provides a way to identify the highest risk patients who stand to gain the most from intervention and should serve as the target population for future trials.

The VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) trial enrolled 72 adults at any of five U.S. centers or at one in Canada. Enrolled patients had a recent stroke or transient ischemic attack in their vertebrobasilar territory plus angiographic evidence of at least 50% stenosis in an extra- or intracranial vertebral or basilar artery. All patients underwent quantitative MR angioplasty of their large vertebrobasilar arteries using software, Noninvasive Optimal Vessel Analysis (NOVA), that measures volumetric flow rates through vessels. Eighteen patients (25%) had low distal flow, defined as a greater than 20% reduction in flow, compared with normal, and 54 patients (75%) who had normal flow.

The study’s primary endpoint was an incident ischemic stroke in the vertebrobasilar territory during 12 months of follow-up. During a median follow-up of 23 months, 10 patients had this type of new stroke.

Among the 18 low-flow patients, four (22%) had a primary endpoint after 12 months, and among the 54 normal-flow patients, 2 (4%) had a primary endpoint after 12 months, a statistically significant difference, Dr. Amin-Hanjani reported at the conference.

In a multivariate analysis, low-flow at baseline linked with a significant, ninefold increased risk for incident stroke, compared with normal-flow patients. The location of the blockage – in the basilar region, vertebral region, or both – had no apparent impact on outcome.

About 30% of ischemic strokes occur in the posterior circulation, and about a third of those are caused by vertebrobasilar disease secondary to atherosclerosis. Overall patients who have had strokes of this type face a 10%-15% rate of new stroke annually despite receiving standard medical treatment, Dr. Amin-Hanjani said.

Dr. Amin-Hanjanihas received research grants from GE Healthcare and VasSol, the company that markets the NOVA software used in VERiTAS. A coauthor on the report has a significant ownership interest in VasSol.

mzoler@frontlinemedcom.com

On Twitter @mitchelzoler

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