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Thrombectomy improved functional outcomes in severe stroke with proximal large-vessel occlusion treated up to 6 hours after stroke onset, the MR CLEAN trial showed.

in the intra-arterial treatment group after adjustment for other factors than with usual care alone (95% CI 1.21-2.30), Diederik W. Dippel, MD, PhD, of Erasmus MC University Medical Center in Rotterdam, the Netherlands, and colleagues found.

Survival with little or no disability as measured by a modified Rankin score of no more than 2 occurred in 32.6% of patients who got intra-arterial treatment compared with 19.1% who got medical treatment alone, they reported online in the .

The intra-arterial treatments used were predominantly retrievable stents (82%) atop IV thrombolytics (87%), with the rest largely accounted for by additional thrombolytics given directly into the affected artery.

Mortality came out similar between groups, and there was no excess risk of symptomatic intracranial hemorrhage with the interventional strategy in the trial.

A Society of NeuroInterventional Surgery release called it the "most significant stroke treatment clinical trial since NINDS-2," which led to approval of IV tissue plasminogen activator (tPA).

"While IV-tPA revolutionized stroke care, it must be administered within 4.5 hours," the statement pointed out. "Neurointerventional surgery can be performed up to 6 hours from the onset of stroke, significantly expanding the treatment window."

It's too soon to call this strategy the standard, though, cautioned , of Germany's University Hospital Heidelberg, in an editorial accompanying the NEJM paper.

"Several similar trials are ongoing," he wrote. "We need and will get results from other well-designed trials, not only to confirm or refute the results of MR CLEAN but also to look at effects in subgroups (according to stroke severity, occlusion site, or time to treatment initiation), for which most single trials are underpowered.

MR CLEAN is the first step in the right direction."

A Change in Direction

That direction hasn't been supported by prior thrombectomy trials.

The and trials both showed no impact of endovascular therapy on survival without disability compared with conventional treatment with IV tPA alone.

The showed no benefit of endovascular mechanical clot removal for large-vessel, anterior-circulation strokes selected by MR or CT imaging.

The reason for the different results in MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands) could have been several, Hacke suggested.

"These trials were criticized for their use of older recanalization devices," he wrote, "which were associated with lower recanalization rates than those found with newer devices such as retrievable stents; for the long interval between the onset of stroke and intervention; and for disappointingly low recruitment rates, which suggested that many suitable patients had been treated outside the trials.

Perhaps most important, two of the trials did not require evidence of an occluded vessel before randomization, thereby making intracerebral treatment futile from the start."

Addressing Quality Issues

MR CLEAN addressed those concerns by using modern thrombectomy devices -- almost all used were retrievable-stent types, which Hacke said have a track record of successful recanalization -- and by quick enrollment because the Dutch government would only pay for thrombectomy in the context of a randomized trial.

The trial required all patients to be able to initiate intra-arterial treatment within 6 hours of onset of a stroke with occlusion of the distal intracranial carotid artery, middle cerebral artery, or anterior cerebral artery proven by CT, MRI, or digital-subtraction angiography.

Of the 500 patients at 16 medical centers in the Netherlands randomized to treatment with intra-arterial treatment plus usual care or usual care alone, almost 90% received intravenous thrombolysis first.

All secondary clinical and imaging outcomes favored the interventional strategy, although Hacke noted that the recanalization rate came in a bit below expected (59% with good reperfusion score compared with 80% or higher in recent case series).

Serious adverse events were no different between groups, although the new ischemic stroke rate at 90 days was higher with intra-arterial treatment (5.6% versus 0.4% among controls).

Procedure-related complications included embolization into new territories in 8.6%, procedure-related vessel dissection in 1.7%, and vessel perforation in 0.9%.

From the American Heart Association:

• Science News from ISC 2014

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