Collateral Flow Associated with Angiographic, Clinical Outcomes in Acute Stroke Patients

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More robust collateral grade is associated with better recanalization, reperfusion, and subsequent clinical outcomes in acute stroke patients, according to a subanalysis of the IMS III trial published online January 28, 2014, ahead of print in Stroke. The researchers conclude that collecting and evaluating angiographic collateral data will be important for future trials.

Results of the Interventional Management of Stroke (IMS) III trial were presented February 7, 2013, at the International Stroke Conference in Honolulu, HI, and simultaneously published online ahead of print in the New England Journal of Medicine. The study was halted after an interim analysis found that endovascular treatment (catheter-delivered thrombolysis or a stent retrieval device) failed to improve outcomes for acute stroke patients when used as add-on therapy with tissue plasminogen activator (t-PA).

For the substudy, investigators led by David S. Liebeskind, MD, of the UCLA Stoke Center (Los Angeles, CA), reviewed angiographic collaterals of 331 patients from the endovascular therapy arm of IMS III, treated from 2006 to 2012. Adequate views of collateral circulation to the ischemic territory were available in 83% (n = 276) of patients. Collateral grade included:

• Grade 0 (no collaterals): 6.9%
• Grade 1: 19.2%
• Grade 2: 39.1%
• Grade 3: 31.9%
• Grade 4: 2.9%

Better Collaterals, Higher Success

Collateral grade was associated with the degree of recanalization of the occluded arterial segment and downstream reperfusion, as well as clinical outcomes at 3 months (table 1).

Table 1. Angiographic and Clinical Outcomes by Collateral Grade

Abbreviations: AOL, arterial occlusive lesion; mTICI, modified Thrombolysis in Cerebral Infarction; mRS, modified Rankin Scale

There was no relationship between collaterals and symptomatic hemorrhagic transformation, though this was limited by the small number of available cases.

After adjustment for systolic BP, collateral score remained significantly associated with both recanalization and reperfusion. Additionally, after adjusting for age, diabetes, NIH Stroke Scale score, and the Alberta Stroke Program Early CT (ASPECTS) score, multivariable analysis confirmed the association between angiographic collateral grade and good clinical outcome (mRS ≤ 2) at 90 days (P = 0.0353).

Important for Future Trial Design

“Our results provide definitive evidence that collateral status is closely related to revascularization success,” Dr. Liebeskind and colleagues write. “Collateral grade . . . is feasible in the vast majority of cases using routine acquisitions or injections.”

The study also confirms “that collaterals are an influential factor in the angiographic and clinical outcomes across a diverse population of cases based on the site of arterial occlusion and particular endovascular strategies, including local thrombolytic, aspiration, and mechanical thrombectomy approaches in combination with intravenous t-PA,” they add.

The authors note that future study is required to evaluate the “potential relationship of collateral grade with history of cardiovascular risk factors, such as hypertension or congestive heart failure, time from stroke onset to treatment, and ASPECTS score . . . because variables may exhibit complex interactions. Similarly, the relationship between blood pressure and collateral grade mandates further consideration.”

Although endovascular therapy does not guarantee successful outcomes in a broad population, the relationship between collateral grade and angiographic and clinical outcomes helps physicians recognize which patients are most likely to benefit from the approach, Dr. Liebeskind and colleagues write. However, they add, “collateral flow by itself is not enough to guarantee who will benefit from endovascular therapy, at least in the time window of patients treated in IMS III.”

Going forward, the authors indicate “the role of collaterals in selection criteria or to modify treatment strategies is an important consideration in the design of future endovascular trials.”

Giving Scientific Credence to the ‘Obvious’

Philip M. Meyers, MD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview that “historically, angiographers have tried to estimate cerebral blood flow based on vessel appearance at catheter angiography.” However, it was eventually determined that even the experts were not good at doing so, he added.

“Many tests have been developed to try to assess cerebral blood flow for purposes of treatment planning and outcome assessment,” Dr. Meyers continued, including CT, perfusion, and magnetic resonance-perfusion imaging. “This study is somewhat of a throwback to the idea that angiographic assessment of collaterals has some value, and the results make sense: people who have better collaterals before they undergo stroke treatment will likely have better outcomes because their brains maintained better perfusion during their strokes.”

The results support the idea that “qualitative assessment of collateral blood flow as a surrogate marker for cerebral blood flow has merit in the assessment of acute stroke patients. It's a statement of the obvious, but it lends scientific credence to the concept.”

Study Details

The time interval from stroke onset to initiation of intravenous t-PA differed by collateral grade (P = 0.0039); this time was longest for subjects with grade 0 (mean 146.9 min) and shortest for subjects with grade 1 (mean 113.2 min). History of hypertension (P = 0.0008) and history of congestive heart failure (P = 0.0411) were associated with poorer baseline collateral grade.

 

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Source:
Liebeskind DS, Tomsick TA, Foster LD, et al. Collaterals at angiography and outcomes in the interventional management of stroke (IMS) III trial. Stroke. 2014;Epub ahead of print.

 

 

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