A new generation tool that restores blood flow and mechanically removes clots from blocked blood vessels in people who have had an acute ischemic stroke, performed dramatically better in a clinical trial than the standard treatment, according to a new study reported in The Lancet this week.

Stroke, where blood supply to the brain becomes restricted, is the fourth leading cause of death in the United States, and is also a common cause of long-term disability. The loss of blood supply leaves tissue starved of oxygen and vital nutrients, and if not restored quickly, the tissue dies off, causing loss of brain function.

Doctors don’t have many tools to deal effectively with strokes, nearly 90% of which are caused by a blood clot. The most-researched treatment approved in the US is a clot-buster known as tissue plasminogen activator, but this drug has to be given within a small time window of 4.5 hours from the start of the stroke, and the window is even smaller in older patients.

If clot-busting drugs are ruled out, then the other option is mechanical retrieval (mechanical thrombectomy), for which the standard treatment uses the Merci Retrieval System.

But in the trial reported in The Lancet, the new device, called Solitaire, performed dramatically better than the Merci system, a result that the researchers describe as a “game changer” for patients who have a stroke.

Lead author Jeffrey L. Saver, director of the University of California – Los Angeles (UCLA) Stroke Center, told the press:

“This new device is significantly changing the way we can treat ischemic stroke.”

“We are going from our first generation of clot-removing procedures, which were only moderately good in reopening target arteries, to now having a highly effective tool,” said Saver, who is also a professor of neurology at the David Geffen School of Medicine at UCLA.

The new tool, called the Solitaire Flow Restoration (FR) Revascularization device, performed so well, that the safety committee overseeing the trial recommended it stop a year early.

The new device is one of a generation of new tools designed to remove blood clots from blocked brain arteries in patients with an ischemic stroke.

Solitaire is a self-expanding stent made with thin curvy wires. The procedure resembles a miniscule fishing expedition that uses the new tool like a net to capture and remove the blood clot.

The surgeon inserts the device into the blocked artery using a thin catheter tube. Once inside, the tool emerges, compresses and traps the clot, and the surgeon pulls it back through the catheter and withdraws, reopening the blocked blood vessel in the process.

Solitaire was approved by the US Food and Drug Administration in March 2012, and is also approved for use in Europe. It is made by made by Covidien, a global company with corporate headquarters in Plymouth, Minnesota, in the US.

The Lancet study reports the results of the Solitaire With the Intention for Thrombectomy (SWIFT) trial, which tested the new tool against the standard mechanical clot remover, the Merci Retrieval System.

The trial was not designed to compare Solitaire or Merci against any drug-based clot busters.

The trial participants were 113 patients with acute ischaemic stroke with moderate to severe effect on the brain. Their average age was 67 (68% males) and they were treated at 17 sites in the US and one in France.

The researchers randomly assigned patients to receive mechanical clot removal either by Solitaire or Merci within 8 hours of stroke symptom onset, between January 2010 and February 2011.

40% of the patients had been given standard clot-busting medication before joining the study, and the rest had not received it.

The time from the beginning of stroke symptoms to the start of the clot-retriever treatment averaged 5.1 hours. The results showed that:

  • Solitaire was effective in 61% of participants (ie it opened blocked vessels without causing symptomatic bleeding in or around the brain). This compares with 24% in the Merci group.

  • Surivival rate three months after a stroke was also better in the Solitaire group (17.2% mortality) than in the Merci group (38.2% mortality).

  • 2% of the Solitaire group had bleeding in the brain compared with 11% in the Merci group.

  • At the 90-day follow-up, overall rates of adverse events, including bleeding in the brain, were similar for both groups.

  • 58% of the Solitaire group had good mental and motor functioning at 90 days, compared with 33% in the Merci group.

  • The Solitaire tool also opened up more vessels when used as a first treatment: that group needed fewer further attempts with other devices or drugs.

The researchers conclude:

“The Solitaire Flow Restoration Device achieved substantially better angiographic, safety, and clinical outcomes than did the Merci Retrieval System. The Solitaire device might be a future treatment of choice for endovascular recanalisation in acute ischaemic stroke.”

The study was funded by Covidien, and two of the researchers were also paid by the company to design and carry out the trial.

Written by Catharine Paddock PhD