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Endovascular clot removal within 8 hours of onset improved outcomes for certain acute ischemic strokes in the REVASCAT trial, although not quite as much as with earlier thrombectomy in several recent trials.

Stent retriever use in small-to-moderate ischemic core anterior circulation strokes , with a 70% higher adjusted odds of a 1 point better score on the modified Rankin scale (mRS) at 90 days, compared with medical treatment alone.

The likelihood of functional independence indicated by a mRS score of 0 to 2 at 90 days more than doubled, with a rate of 43.7% compared with 28.2%, Antoni Davalos, MD, of the Hospital Germans Trias I Pujol in Barcelona, and colleagues found.

Their findings from the trial embedded within a population-based registry were reported online in the New England Journal of Medicine in conjunction with presentation at the European Stroke Organisation conference in Glasgow.

The treatment effect was lower than seen in the SWIFT PRIME, ESCAPE, and EXTEND IA studies reported out of the International Stroke Conference in February, Davalos' group noted.

In the SWIFT PRIME trial, for example, the rate of functional independence with an mRS score of 0 to 2 was (P<0.001). The full results were published alongside REVASCAT in NEJM and at the European stroke meeting, confirming the preliminary findings presented at the earlier conference.

One reason may have been that imaging was not centrally adjudicated, which appeared to have allowed in a number of patients who met exclusion criteria because they didn't have the kind of large-vessel but not large core strokes most likely to benefit, they explained.

"This factor, in conjunction with longer times from symptom onset to reperfusion, centrally adjudicated outcomes, and imbalances in the proportion of patients with extracranial occlusion of the internal carotid artery, may explain the lower treatment effect seen in our study," they wrote.

However, "the magnitude of benefit that we saw in our study was similar to that observed in MR CLEAN, with which our study shared many features," they added.

MR CLEAN, the first positive trial for thrombectomy after a spate of negative trials in 2013, didn't require much by way of imaging to confirm small core infarct and had about half the impact as seen in the more recent trials that did use well-defined CT selection criteria.

Technology and patient selection have been key reasons for the "sea change," , chair of neurology at University Hospitals Case Medical Center in Cleveland, wrote in an .

"Stent-retriever device technology results in faster, more complete recanalization ... as compared with intravenous t-PA alone or earlier- generation thrombectomy devices," he noted.

All four trials randomized patients to medical therapy alone (largely with alteplase [Activase] thrombolysis) or with endovascular treatment. Thrombectomy ranged from any available technology in MR CLEAN to only the Solitare FR or newer generation Solitare 2 device in SWIFT PRIME.

All the trials showed no excess mortality and no increase in symptomatic intracranial hemorrhage. In the 206-patient REVASCAT trial, symptomatic intracranial hemorrhage occurred in 1.9% of patients in both treatment groups.

Exactly what the best imaging criteria are for selection in clinical practice isn't yet settled, but "the rapid demonstration of large-vessel occlusion must now become part of the standard evaluation of acute stroke," he wrote.

Another crucial shift has been bringing in the "time is brain" emphasis on speed in thrombolysis, Furlan noted.

The vast majority of patients in these five trials were randomized within 6 hours of onset. SWIFT PRIME even achieved an emergency department door-to-groin puncture time of 90 minutes.

"This goal requires stroke-workflow efficiencies not yet in place in many hospitals," Furlan noted. Emergency response systems will also need to address triage and transport, he pointed out.

"How far the time window for endovascular treatment can be extended with the use of imaging selection criteria is also unclear," he wrote. "Regardless, earlier is always better, because time is brain. Pending the resolution of this issue, it is probably best to avoid initiating endovascular therapy in patients with large (>50 to 70 ml) infarct cores as assessed by means of CT or MRI or an ASPECTS of 4 or less, beyond 6 hours from stroke onset."

From the American Heart Association