MR CLEAN Substudy Shows Benefit of Larger Thrombi Retrieval During Intra-Arterial Treatment

September 1, 2015—The European Society of Cardiology (ESC) announced that findings from a substudy of the MR CLEAN trial demonstrated that retrieval of larger thrombi during intra-arterial treatment (IAT) is associated with improved neurological recovery after acute ischemic stroke. The MR CLEAN substudy data were presented by Anouchska Autar, MD, from the Erasmus Medical Center in Rotterdam, the Netherlands, at the ESC Congress 2015 held August 20 to September 2 in London, United Kingdom.

MR CLEAN, a randomized trial of IAT for acute ischemic stroke, was published in January 2015 by Olvert A. Berkhemer, MD, et al in The New England Journal of Medicine (2015;372:11–20). The MR CLEAN investigators concluded that in patients with acute ischemic stroke caused by a proximal intracranial occlusion of the anterior circulation, IAT administered within 6 hours after stroke onset was effective and safe.

In the ESC announcement, Dr. Autar commented, “MR CLEAN was the first trial to show the benefit of IAT to remove blood clots within 6 hours after a stroke. IAT, which was given against a background of standard care including intravenous tissue plasminogen activator if indicated, led to better restoration of blood flow and improved functional outcome when compared to no IAT.”

As noted in the ESC press release, thrombi retrieved during the MR CLEAN trial were collected for the current substudy to investigate the relationship between the macroscopic appearance of thrombi retrieved during IAT, cause of stroke, and clinical outcome. Measures of macroscopic appearance included length, width, area, and numbers of particles the thrombus had broken into. Neurological recovery was assessed using the National Institutes of Health Stroke Severity Scale.

The study included 35 collections of thrombi from 35 patients who had undergone IAT after an acute ischemic stroke. Most of the patients had a severe stroke, of which 49% were of cardiac origin and 20% were due to atherosclerosis.

The investigators reported that patients whose stroke was caused by atherosclerosis had significantly longer and larger thrombi (P = .0035 and P = .045, respectively) than those with stroke from other causes. “This could be because patients with atherosclerosis have more diseased arteries and this may influence thrombus size,” stated Dr. Autar.

The investigators also found that patients from whom longer and wider thrombi were retrieved had significantly improved neurological recovery at discharge after IAT, compared to those with smaller thrombi (P = .03 and P = .04, respectively). Dr. Autar advised, “This finding is particularly important because it indicates that the larger the pieces that you retrieve, the better this is for your patient.”

An increased number of particles retrieved during IAT showed a trend towards a worse neurological recovery at discharge, although the association was not significant (P = .079). Dr. Autar noted, “Together, this suggests that some emboli are more likely to disintegrate and the smaller particles may embolize and obstruct the microvasculature of the brain, leading to incomplete recovery.”

In the ESC announcement, Dr. Autar concluded, “Our study shows that retrieval of larger thrombi during IAT is associated with improved neurological recovery at discharge in patients with acute ischemic stroke. The findings indicate that a simple parameter such as thrombus size might influence the decision to give or refrain from additional thrombolysis. This needs to be verified of course in larger trials.”