An incidental diagnosis of intracranial atherosclerotic stenosis in stroke-free individuals should trigger a thorough assessment of vascular health, according to the authors of a study identifying risk factors and vascular event risk in asymptomatic ICAS.

That conclusion emerged from data collected on more than 1,000 stroke-free participants in NOMAS (Northern Manhattan Study), a trial that prospectively followed participants who underwent a brain magnetic resonance angiogram (MRA) during 2003-2008.

In ICAS patients with stenosis of at least 70%, even with aggressive medical therapy, the annual stroke recurrence rate is 10%-20% in those with occlusions and at least three or more vascular risk factors. This high rate of recurrent vascular events in patients with stroke caused by ICAS warrants greater focus on primary prevention and targeted interventions for stroke-free individuals at highest risk for ICAS-related events, the investigators concluded.

Identify High-Risk ICAS

Using NOMAS data, the investigators, led by Jose Gutierrez, MD, MPH, tested the hypothesis that stroke-free subjects at high risk of stroke and vascular events could be identified through the presence of asymptomatic ICAS. NOMAS is an ongoing, population-based epidemiologic study among randomly selected people with home telephones living in northern Manhattan.

During 2003-2008, investigators invited participants who were at least 50 years old, stroke free, and without contraindications to undergo brain MRA. The 1,211 study members were followed annually via telephone and in-person adjudication of events. A control group of 79 patients with no MRA was also identified with similar rates of hypertension, diabetes, hypercholesterolemia and current smoking.

Mean age was about 71 years (59% female, 65% Hispanic, 45% any stenosis). At the time of MRA, 78% had hypertension, 25% had diabetes, 81% had hypercholesterolemia, and 11% were current smokers.

Researchers rated stenoses in 11 brain arteries as 0, with no stenosis; 1, with less than 50% stenosis or luminal irregularities; 2, 50%-69% stenosis; and 3, at least 70% stenosis or flow gap. Outcomes included vascular death, myocardial infarction, ischemic stroke, cardioembolic stroke, intracranial artery disease stroke (which combined intracranial small and large artery disease strokes), and any vascular events (defined as a composite of vascular death, any stroke, or MI).

Greater Stenosis Denotes Higher Risk

Analysis found ICAS to be associated with older age (odds ratio, 1.02 per year; 95% confidence interval, 1.01-1.04), hypertension duration (OR, 1.01 per year; 95% CI, 1.00-1.02), higher number of glucose-lowering drugs (OR, 1.64 per each medication; 95% CI, 1.24-2.15), and HDL cholesterol(OR, 0.96 per mg/dL; 95% CI, 0.92-0.99). Event risk was greater among participants with ICAS of at least 70% (5.5% annual risk of vascular events; HR, 2.1; 95% CI, 1.4-3.2; compared with those with no ICAS), the investigators reported in the Journal of the American College of Cardiology.

Furthermore, 80% of incident strokes initially classified as small artery disease occurred among individuals with evidence of any degree of ICAS at their baseline MRI, the investigators noted. They found also that individuals with ICAS who had a primary care physician at the time of their initial MRI had a lower risk of events. Frequent primary care visits, they observed, might imply greater control of risk factors and other unmeasured confounders, such as health literacy, health care trust, access, and availability.

Incidental ICAS Should Trigger Vascular Assessment

An incidental diagnosis of ICAS in stroke-free subjects should trigger a thorough assessment of vascular health, the investigators concluded. They commented also that prophylaxis of first-ever stroke at this asymptomatic stage “may magnify the societal benefits of vascular prevention and decrease stroke-related disability and vascular death in our communities.”

“The big gap in our knowledge,” Tanya N. Turan, MD, professor of neurology at Medical University of South Carolina, Charleston, wrote in an accompanying editorial “is understanding the pathophysiological triggers for an asymptomatic stenosis to become a high-risk symptomatic stenosis. Until that question is answered, screening for asymptomatic ICAS is unlikely to change management among patients with known vascular risk factors.” In an interview, she observed further that “MRI plaque imaging could be a useful research tool to see if certain plaque features in an asymptomatic lesion are high risk for causing stroke. If that were proven, then it would make more sense to screen for ICAS and develop specific therapeutic strategies targeting high-risk asymptomatic plaque.”

Focus on Recurrent Stroke Misplaced

Gutierrez said in an interview: “In the stroke world, most of what we do focuses on preventing recurrent stroke. Nonetheless, three-fourths of strokes in this country are new strokes, so to me it doesn’t make much sense to spend most of our efforts and attention to prevent the smallest fractions of strokes that occur in our society.”

He stressed that “the first immediate application of our results is that if people having a brain MRA for other reasons are found to have incidental, and therefore asymptomatic, ICAS, then they should be aggressively treated for vascular risk factors.” Secondly, “we hope to identify the patients at the highest risk of prevalent ICAS before they have a stroke. Among them, a brain MRI/MRA evaluating the phenotype would determine how aggressively to treat LDL.”

Gutierrez, professor of neurology at Columbia University Irving Medical Center, New York, noted that educating patients of their underlying high risk of events may have the effect of engaging them more in their own care. “There is evidence that actually showing people scans increases compliance and health literacy. It’s not yet standard of care, but we hope our future projects will help advance the field in the primary prevention direction,” he said.

This work was supported by the National Institutes of Health. The authors reported that they had no relevant financial disclosures.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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