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NEW ORLEANS -- CT angiography (CTA) imaging should be included with brain CT for early detection of severe arterial stenosis in patients presenting with transient ischemic attack or minor stroke, researchers suggested.

Of 491 patients with transient ischemic attack (TIA) or minor stroke, the median time to a recurrent stroke was one day, Shelagh B. Coutts, MD, ChB, from Foothills Hospital in Calgary, Alberta, Canada and colleagues found.

However, the median time from stroke onset to CTA imaging was 5.5 hours versus 17.5 hours for diffusion-weighted MRI, Coutts reported at the American Stroke Association's International Stroke Conference and simultaneously published online in Stroke: Journal of the American Heart Association.

Coutts and colleagues pointed out that because the majority of these recurrent strokes occur within 48 hours after TIA, a quick assessment of the risk is imperative. Imaging is one way to stratify that risk.

Diffusion-weighted MRI is the gold standard for diagnosing acute stroke. In fact, an American Heart Association/American Stroke Association scientific statement in 2009 stated that MRI is preferred for evaluating TIA patients within 24 hours of symptom onset.

However, CT scanners are much more widely available in emergency departments in the U.S., Coutts said. And when evaluating these patients very early in their presentation, the distinction between TIA and minor ischemic stroke is "largely irrelevant."

She said that new treatments are needed for these "unstable" patients and "waiting for these patients to stabilize over the next 24 hours misses the patients at highest risk."

The researchers suggested that reliance on motor or speech symptoms to define TIA could be antiquated. The 2009 AHA/ASA scientific statement "redefined the definition of TIA based on MRI imaging results," Mark Alberts, MD, the medical director of the stroke program at Northwestern Memorial Hospital in Chicago, told 乌鸦传媒. Alberts was a co-author of the statement.

CTA, which uses contrast media to image the vasculature, adds less than five minutes to a brain CT scan, which is typically used to rule out hemorrhagic stroke. And CTA can easily identify large artery disease, which is "the stroke mechanism with the highest risk of early stroke recurrence," the investigators wrote.

The current study was undertaken to determine whether CTA could predict recurrent stroke and to compare it with diffusion-weighted MRI.

Eligibility criteria included a high-risk TIA focal weakness or speech disturbance lasting more than five minutes or minor ischemic stroke (National Institute of Health Stroke Scale score <3). All 491 patients were referred to Foothills Medical Center during a period of 29 months.

The mean age of the patients was 69 and those who had a positive CT/CTA scan were significantly older than those who had negative scans (age 76 versus 66, P=0.015).

Other significantly distinguishing baseline characteristics for those with positive CT/CTA scans included:

• Ongoing symptoms at first assessment (P=0.007)
• Clopidogrel treatment (P<0.0001)
• Combined aspirin and clopidogrel treatment (P<0.0001)
• Statin treatment (P<0.0001)

"It was not protective for these patients to be treated with aspirin, clopidogrel, or both," Coutts said.

She noted that about 85% of patients were treated with aspirin for more than one day, and that everybody received at least one dose of an antiplatelet drug in the emergency department.

Just about half the patients were diagnosed with TIA and half with ischemic stroke. Six percent of patients underwent carotid stenting or endarterectomy, and none of them had a recurrent stroke.

In the rest of the patients, there were 36 primary outcome events. More than half of these (53%) were categorized as "progression of the presenting event" and 17 as "distinct recurrent strokes."

Another 53% of these primary outcome events resulted in a modified Rankin Scale score of 2 or greater at 90 days.

The various clinical and imaging parameters that were significant for recurrent stroke were:

• Ongoing symptoms at first assessment (HR 2.2)
• Intracranial occlusion or stenosis ≥50% (HR 5.1)
• Intracranial occlusion (HR 6.1)
• Extracranial carotid occlusion or stenosis ≥50% (HR 2.4)
• Positive CT/CTA (HR 4.0)
• Positive diffusion-weighted MRI (HR 2.2)

However, in the multivariable analysis, only a positive CT/CTA scan remained a predictor of recurrent stroke.

Using receiver operating characteristic analysis, CT/CTA and diffusion-weighted MRI were not significantly different in their discriminative value in predicting stroke.

The study was limited because not everybody underwent MR imaging and researchers imputed results, but they said the imputation did not "substantially change the conclusion, only the precision of the point estimate." Also, the results cannot be extrapolated to transient sensory events.

From the American Heart Association: