Endovascular Therapy After Acute Ischemic Stroke

MR CLEAN Study Shows Benefits of Adding Endovascular Therapy Within 6 Hours

Mark J. Alberts, MD


January 14, 2015

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Hello, and welcome to this Medscape stroke update. My name is Dr Mark Alberts, Vice Chair of Neurology at UT Southwestern Medical Center in Dallas, Texas. As I promised in a blog just a few weeks ago, the results of the MR CLEAN study were published in January of this year in the New England Journal of Medicine.[1]

MR CLEAN is an important study. It was a prospective randomized trial of interventional therapy plus intravenous (IV) recombinant tissue plasminogen activator (rt-PA) vs IV rt-PA alone for patients with acute ischemic stroke due to a large artery anterior circulation occlusion. Most patients had an middle cerebral artery (MCA) M1 occlusion.

What they did, essentially, is give the vast majority of folks in both arms of the study—about 233 in one arm and 260 in the other arm—IV rt-PA within 4.5 hours. Then, for the interventional group, they went on to some endovascular therapy, the vast majority of which was using a stentriever to remove the clot. For the control group, they just gave IV rt-PA alone.

The primary endpoint was a shift in the rank and score, as well as a rank and score of 0 to 2. Both groups were well matched in terms of age, time to treatment, and baseline risk factors. There were some minor imbalances, but nothing major.

So what was found at the end of the day? Well, there was a statistically significant shift in the modified ranking, from a 4 in the rt-PA only group to a 3 in the rt-PA plus endovascular intervention group. This was statistically significant. Furthermore, if you look at folks who were independent at 90 days to find as a modified ranking of 0 to 2, this number went from 19% in the rt-PA only group to about 33% in the rt-PA plus endovascular treatment group. This also was statistically significant.

In terms of safety—bleeding and other complications—these were relatively rare and were equal, essentially, in both groups. So this is a very good outcome.

This is the first really well-done prospective, randomized study of endovascular therapy using modern devices, such as stentrievers, that have shown both efficacy and safety.

Nonetheless, there are still some challenges. In the endovascular treatment group, between 75% and 58% of patients showed opening of the blood vessel at various times by various measures. Yet again, many of those patients did not clearly get better: Only 33% of them were independent at 90 days. Clearly, opening up the vessel in everybody does not equal a good outcome. Perhaps this is one of the deficiencies of this study: They did not do any advanced brain imaging to see who has an ischemic penumbra—who has salvageable tissue and who does not.

Another point to keep in mind is that this study is the first of many recent studies using the stentrievers that are to be published in the upcoming weeks and months. We'll have to see what they all show.

Some people have called for a halt in all further studies, thinking that this issue of endovascular therapy for acute ischemic stroke has been asked and answered with this and perhaps other studies. Werner Hacke wrote a very nice editorial to this in the New England Journal of Medicine,[2] where he essentially states that this is not necessarily the end of the story, but a very good chapter in an evolving book. I think that may be the case pending the results of other studies.

Perhaps this is a nice new year's gift that we have the first really well-done study of endovascular therapy using good baseline therapy with IV rt-PA and a 6-hour treatment window. We'll have to see how the story evolves as we go forward.

Thank you very much for joining me for this Medscape Stroke Update. Please write your comments below.


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