Conference Coverage

Three trials cement embolectomy for acute ischemic stroke

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Results warrant embolectomy scale-up

Many U.S. centers have interventionalists who already perform endovascular treatments within intracerebral arteries, but the issue is can they do this form of embolectomy in the high-quality, highly-reliable, rapid way that it was done in these trials? Stent-retriever catheters are relatively straightforward to use by operators who are experienced doing vascular procedures in the brain, but they don’t deliver this treatment by themselves. You need a team that is focused on doing it quickly, and that will be the kind of training we’ll need to roll out this treatment broadly. We achieved it for stroke thrombolytic treatment through the Target Stroke program (JAMA 2014;311:1632-40), so we know that we can achieve this sort of goal. Delivering embolectomy requires more people and more technology than thrombolysis, but it is not rocket science; it just needs a system.

Dr. Lee H. Schwamm

Embolectomy will not replace routine thrombolysis treatment; it will piggyback on top of it. The percentage of patients with a proximal occlusion in a large artery is relatively small. The results we have seen suggest that using embolectomy plus thrombolysis has no adverse-effect downside, compared with thrombolysis alone. Once routine use of embolectomy becomes established, we can directly compare catheter treatment only against combined embolectomy and thrombolysis. My impression today is that what we’d compare is transporting stroke patients directly to a center that can perform embolectomy against taking patients to the closest center that can treat them with thrombolysis and then transporting them to the center that performs embolectomy.

The results of these three new studies plus the previously-reported results from MR CLEAN are not exactly a game changer, because many centers were already performing embolectomy but in a limited way. Now we have the data to give us confidence to do it routinely and to know which patients to select for embolectomy. Because many centers are already doing this, it will not take 5 years to diffuse the technology.

Embolectomy is already a treatment cited in the guidelines, but now it will be a level 1A recommendation.
The significance of the new reports is that they will have a dramatic impact on public health systems and in the triage of patients with stroke. It will affect how patients get triaged, and will allow us to identify which patients should go to which centers. I believe we will soon develop clinical examination tools that will allow prehospital providers to discern patients with mild strokes who can go to the nearest center that can administer thrombolysis and which patients need to go to comprehensive centers that can perform embolectomy. We now need to do what we did for thrombolysis, and help centers develop the expertise to do embolectomy as a team and to shave minutes off the delivery at every step of the process. It’s clear that it is the time from stroke onset to getting the artery open that is the key to improved patient outcomes.

If I have my way, we will launch later this year a big effort to focus on improving embolectomy delivery. Now that we know for certain that it works we need to turn the crank and make sure that as many patients as possible who qualify get this treatment.

Dr. Lee H. Schwamm is professor of neurology at Harvard Medical School, and director of acute stroke services at Massachusetts General Hospital, both in Boston. He is a consultant to Penumbra and has received research support from Genentech. He made these comments in an interview.


 

AT THE INTERNATIONAL STROKE CONFERENCE

References

NASHVILLE, TENN. – Treatment of selected patients with acute ischemic stroke underwent a dramatic, sudden shift with reports from three randomized, controlled trials that showed substantial added benefit and no incremental risk with the use of catheter-based embolic retrieval to open blocked intracerebral arteries when performed on top of standard thrombolytic therapy.

The three studies, each run independently and based in different countries, supported the results first reported last October and published online in December (N. Engl. J. Med. 2015;372:11-20) from the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) study. These were the first contemporary trial results to show a jump in functional outcomes with use of a stent retriever catheter to pluck out the occluding embolus from an artery in the stroke patient’s brain to restore normal blood flow.

All three of the newly-reported studies stopped before reaching their prespecified enrollment levels because of overwhelming evidence for embolectomy’s incremental efficacy.

With four reports from prospective, randomized trials showing similar benefits and no added harm to patients, experts at the International Stroke Conference uniformly anointed catheter-based embolectomy the new standard of care for the small percentage of acute, ischemic-stroke patients who present with proximal, large-artery obstructions and also match the other strict clinical and imaging inclusion and exclusion criteria used in the studies.

Dr. Mayank Goyal Mitchel L. Zoler/Frontline Medical News

Dr. Mayank Goyal

“Starting now, in patients with an acute ischemic stroke due to proximal vessel occlusion, rapid endovascular treatment using a retrieval stent is the standard of care,” Dr. Mayank Goyal declared from the plenary-session podium. He is a professor of diagnostic imaging at the University of Calgary (Canada) and an investigator in two of the three trials presented at the conference, which was sponsored by the American Heart Association.

“Today the world changed. We are now in a new era, the era of highly-effective intravascular recanalization therapy,” said Dr. Jeffrey L. Saver, professor of neurology and director of the Stroke Center at the University of California, Los Angeles, and lead investigator for one of the new studies.

In three of the four studies, the researchers did not report specific numbers on how selective they were in focusing in on the ischemic stroke patients most likely to benefit from this treatment, but the one study that did, EXTEND-IA (Extending the Time for Thrombolysis in Emergency Neurological Deficits – Intra-Arterial), run at nine Australian centers and one in New Zealand, showed the extensive winnowing that occurred. Of 7,796 patients with an acute ischemic stroke who initially presented, 1,044 (13%) were eligible to receive thrombolytic therapy (alteplase in this study). And from among these 1,044 patients, a mere 70 – less than 1% of the initial group – were deemed eligible for randomization into the embolectomy trial. The top three reasons for exclusion of patients who qualified for thrombolytic treatment from the trial was an absence of a major-vessel occlusion (45% of the excluded patients), presentation outside of the times when enrollment personnel were available (22%), and poor premorbid function (16%).

Dr. Jeffrey L. Saver Mitchel L. Zoler/Frontline Medical News

Dr. Jeffrey L. Saver

But subgroup analyses in three of the four studies (EXTEND-IA with a total of 70 patients was too small for subgroup analyses) showed no subgroup of patients who failed to benefit from embolectomy, including elderly patients who in some cases were nonagenarians.

The unusual confluence of having four major trials showing remarkably consistent results meant that the stroke experts gathered at the meeting focused their attention not on whether stent retrievers should now be widely and routinely used in appropriate patients but instead on how this technology will roll out worldwide.

“From here on out we are obligated to treat patients with this technology at centers that can do this, and we are obligated to have more centers that can provide it,” said Dr. Kyra J. Becker, professor of neurology and neurological surgery and codirector of the Stroke Center at the University of Washington, Seattle. Dr. Becker had no involvement in any of the stent retriever trials. “I had been a doubter of this technology,” primarily because results reported at the International Stroke Conference a couple of years ago failed to prove the efficacy of clot retrieval in ischemic stroke patients, she noted. “Our ability to select appropriate patients and do it in a timely fashion hadn’t gotten to where it had to be until now,” Dr. Becker said in an interview.

“We only enrolled patients with blockages, we treated them quickly, and we used much better devices to open their arteries,” Dr. Saver added, explaining why the new studies succeeded when earlier studies had not.

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