Harvard's Dr. Brian Walcott Summarizes a Landmark Trial in Neurology

November 19, 2014

brian walcott, harvard, neurology, reseearch, docphin

Brian Walcott is a senior resident in neurological surgery at the Massachusetts General Hospital/Harvard Medical School, where he specializes in the care of patients suffering from diseases of the brain, cerebral blood vessels, skull base, and spine. His research interest is in vascular biology and he has developed various zebrafish models to study vascular malformations and the vascularity of cancer. He is the author of more than 75 papers in international peer reviewed journals.  He is passionate about medical education and was recently awarded the resident teacher of the year award from the Harvard Medical School class of 2012.  Brian is a Docphin Ambassador. 

Trial: Trevo versus Merci retrievers for thrombectomy revascularisation of large vessel occlusions in acute ischaemic stroke (TREVO 2): a randomised trial.

Authors: Raul G Nogueira, Helmi L Lutsep, Rishi Gupta, Tudor G Jovin, Gregory W Albers, Gary A Walker, David S Liebeskind and Wade S Smith

Journal: Lancet

Date: August 2012

Study relevance

Acute cerebral ischemia (stroke) is a major cause of morbidity and mortality worldwide.  The mainstay of medical therapy is with intravenous administration of recombinant tissue plasminogen activator (rt-PA) to establish revascularization (reperfusion). Despite this, the use of rt-PA is successful in less than half of cases when administered intravenously. For patients that do not qualify for rt-PA, or for whom it is not successful, endovascular therapy can be considered.

Traditional techniques to perform thrombectomy include the Merci Retriever (Merci; Concentric Medical, CA, USA) and the Penumbra System (Penumbra; Penumbra, CA, USA). Though revascularization rates with these devices are excellent, clinical outcomes have been discordant.  While revascularization rates of 48% can be achieved with the Merci device, a modified Rankin scale (mRS) score of ≤ 2 is observed for only 28% of patients at 90 days. Similarly, the Penumbra device yields a revascularization rate of 82%, but only 25% of patients have a mRS ≤ 2 at 90 days.

This randomized trial highlights the next generation of endovascular stroke therapy devices known as “stentrievers” that are poised to revolutionize the treatment of severe strokes.

Results

In this study 178 patients with severe acute stroke (mean National Institutes of Health Stroke Scale score = 18) were randomly assigned to endovascular stroke treatment either with the Trevo Pro Retrieval System (Trevo; Stryker, Kalamazoo, MI, USA) or the Merci device.  Major findings of the study included:

  • No significant difference between the two groups in terms of the primary safety endpoints
  • Trevo group achieved significantly better reperfusion (86% vs 60%) and higher rates of long-term functional independence (40% vs 22%) when compared to the Merci device
  • No difference in mean time to reperfusion between the two treatment arms

Discussion

Retrievable stents, known as stentrievers, are a novel FDA approved technology used to perform mechanical thrombectomy.  Unlike prior devices that required clot extraction to achieve reperfusion, stentrievers facilitate the immediate restoration of blood flow via expansion of a stent within the clot.  The stent integration into the clot also allows for subsequent clot and stent extraction, without any need for permanent device implantation. 

This study is one of two large randomized trials published in the Lancet in 2012 that suggest the superiority of the stentriever technology over its predecessor, the Merci device.  Fundamentally, it is advantageous to utilize thrombectomy devices with faster revascularization times, as the old adage “time is brain” is important when maximizing clinical outcomes.  However, despite the popular perception that the Trevo device is technically easier to use, there was not a statistical difference in the time to reperfusion between the groups.  It is likely that the better outcomes at 24 hours, shorter hospital stays, and improved independence are associated with the increased frequency and extent of reperfusion found with the Trevo device. 

While the results of this study are promising, cautious optimism must be exercised with any proposed radical change in clinical management.  It is increasingly being recognized that any single source, no matter the quality of the study, should not be used to guide clinical management.  The “gold standard” for clinical efficacy is really the reproducibility of any comparison between groups.  With this in mind, stentrievers are on a trajectory to result in paradigm change in the treatment of stroke.

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