The most common treatment for stroke involves taking a drug that dissolves the blood clot, causing the artery to reopen. However, such drug treatment is substantially effective only within three hours after the onset of stroke, and is not suitable for all patients. Moreover, this type of treatment frequently fails to dissolve the larger blood clots which more often cause the disabling strokes.
These problems have led clinicians to try a different approach to stroke treatment, whereby the blood clot is removed by a mechanical device inserted through the groin into the blood vessel, which opens the blockage and restores blood flow to the brain. The device is subsequently removed from the body, along with the blood clot.
In 2004, a corkscrew-shaped flow restoration device called the Merci retriever was approved by the FDA for use in the US, and has since been used in thousands of stroke patients worldwide for whom traditional drug treatment has failed or would not be suitable. The two new Lancet papers reveal that scientists have now developed the next generation of mechanical clot retrievers, which have the potential to offer huge improvements in restoring blood flow, and consequent improvements in patient outcomes.
One of the trials (SWIFT), was led by Dr Jeffrey Saver of the UCLA Stroke Center in Los Angeles, USA, and tested the efficacy of a flow restoration device called Solitaire. When deployed, the device – which consists of a self-expanding wire mesh, guided to the relevant blood vessel via a catheter – traps the blood clot in its structure, and can then be removed, taking the blood clot with it.
In the double-blind, randomised trial of 113 patients, the researchers compared the performance of the Solitaire device to the Merci retriever. Patient outcomes were significantly improved in the group who had been treated with the Solitaire device, with 58% being assessed as having a good neurological outcome after three months, compared to 33% of those treated with the Merci retriever; patient deaths were also reduced, from 38% with Merci to 17% with Solitaire.
In the other trial (TREVO 2), a team of scientists led by Raul Nogueira of the Marcus Stroke and Neuroscience Center in Atlanta, USA, compared the effectiveness of a device called Trevo – which works in a broadly similar way to the Solitaire device – to that of the Merci retriever. The chance of having a fully independent life after the stroke was significantly higher with the Trevo (40%) as compared to the Merci (22%) treatment.
Both Trevo and Solitaire devices were significantly better at restoring blood flow (reperfusion) in affected arteries when compared to the Merci device, although the two trials used different definitions of reperfusion and good neurological outcomes, precluding any direct comparison between the Trevo and Solitaire devices on the basis of these studies.
Critically, both devices appear to have a similar or better safety profile when compared to the Merci retriever. Both devices have been cleared for general clinical use in the US and Europe, and the results suggest that if the findings are confirmed by further studies, significant improvements could be forthcoming in stroke patients for whom drug treatment is ineffective.
In a linked Comment published alongside both papers, Philip Gorelick of the Hauenstein Neuroscience Centre in Grand Rapids, USA, remarks that: "SWIFT and TREVO 2 are major steps forward in the successful treatment of acute ischaemic stroke, and pave the way for new treatment options and further validation by additional trials."
Dr Jeffrey Saver, UCLA Stroke Center, Los Angeles, USA
T) +1 310 794 6379 E) jsaver@ucla.edu
Dr Raul Nogueira, Marcus Stroke and Neuroscience Center, Emory University School of Medicine, Atlanta, USA
T) +1 404 616 4013 E) rnoguei@emory.edu
Dr Philip Gorelick, Hauenstein Neuroscience Centre, Grand Rapids, USA
T) +1 616 685 6455 E) pgorelic@trinity-health.org
Journal
The Lancet