The devices are fairly similar to each other in that they both have a stent-like design, using a tiny wire cage instead of a coil. With the help of a catheter, the device is snaked up from the groin in the artery all the way to the brain. The clot is pushed up against the walls of the artery and enmeshed in the wires, allowing doctors to pull the clot back out of the groin. After the device is withdrawn, the blocked blood vessel reopened.
In two separate trials, these new devices appeared to do a better job of restoring blood flow to the brains of patients with ischemic stroke than the currently approved device, Merci Retriever, also made by Stryker.
The Swift study compared Solitaire with Merci Retriever.
Researchers randomly assigned 113 stroke patients at 18 hospitals to receive either Solitaire or Merci therapy, between January 2010 and February 2011. The patients' average age was 67, and 68% were male. The time from the beginning of stroke symptoms to the start of the clot-retriever treatment averaged 5.1 hours.
Of the 113 patients, 58% had good brain function after three months, compared with 33% of those treated with the standard Merci Retriever, as well as a lower death rate. There was a 17.2% mortality rate with the new device, compared with a 38.2% rate with the older one.
The device opened blocked vessels without causing symptomatic bleeding in or around the brain in 61% of patients. Merci was effective in 24% of cases.
The Swift trial was halted in September 2011 when pre-specified criteria for safety and efficacy were met.
The Trevo2 trial compared Trevo Pro to Merci Retriever. This study in 178 patients showed almost double the chance of living independently after treatment.
Stroke is a disaster
Every year brings nearly 800,000 new stroke patients in North America. That's one every 40 seconds.
Stroke is the largest single cause of severe neurological disability and the third-leading cause of death in the United States. Stroke accounts for an estimated $74 billion annually in related costs of treatment and additional assistance. Three out of every four stroke patients' ability is impaired to perform the activities of daily life.
Strokes are caused by a sudden drop in the flow of blood to the brain resulting from a clot or, less often, bleeding. A stroke is sometimes called a "brain attack."
One in every three stroke patients is under the age of 65. There are about 5.4 million stroke survivors in the United States and 15 million worldwide.
Once symptoms start, there's only a tiny window of time for stroke victims to get life-saving treatment.
Doctors have very few proven treatment methods. The standard for treating acute ischemic stroke is an intravenous injection of the clot buster drug tissue plasminogen activator or tPA which dissolves the blood clot. In order to get that, the patient has to get to the hospital in 4.5 hours from the start of the symptoms.
The reason for the time window is that giving a strong blood thinner like tPA during a stroke can cause bleeding inside the brain. The longer a patient waits to get treatment, the more likely that the risks of treatment will outweigh the benefits.
Patients with large vessel blockage strokes poorly respond to the drug and are candidates for treatment with the Trevo or Solitaire device. Clot-busting drugs only partially reopen 40% of large blocked arteries. The new devices partially reopen 70-90% of large blocked arteries.
Also, the devices can be used in patients in whom it is not safe to give 'clot busting' drugs, such as patients on bloodthinners, patients who had recent surgery, and patients who are between 4.5 to eight hours after stroke onset.
Merci Retriever, the only approved mechanical device in the past few years, generated a healthy skepticism among doctors about mechanical devices. The device was reasonably successful reopening vessels compared to the drug, but it failed in follow up statistics.
Analysis of the National Inpatient Sample of almost 4000 patients who received endovascular clot retrieval therapy for acute ischaemic stroke showed that about 75% had either died in hospital or were discharged to long-term care facilities. The new generation of devices substantially improve on that.
Long road ahead
In spite of the new devices, there is plenty left to do. For one, in the United States, only about 3% of stroke patients end up getting treated. Most of them are ineligible because they come to the hospital after the 4.5 time window. Even the 8 hours window is really hard to keep for most people or hospitals for that matter.
New devices, drugs and procedures are urgently needed. There is hope for new development. The clinicaltrials.gov website lists over 3,500 trials ongoing related to stroke. A small Australian drug study particularly stands out. It was a 3 year study in 75 patients and the findings were published in March 2012 in the New England Journal of Medicine.
The study tested Tenecteplase (TNK) which is an enzyme used as a thrombolytic drug, on stroke victims. Tenecteplase, a genetically engineered mutant tissue plasminogen activator, is an alternative thrombolytic agent to tPA. It is commonly used in heart patients, but researchers at Newcastle University in Australia had a significant breakthrough in treating stroke patients with it, with some people showing "Lazarus-like" recoveries. Some stroke victims using Tenecteplase made almost miraculous recoveries within days. Larger trials will follow up.
In its annual shareholder meeting in April 2012, Curt Hartman, Stryker's interim CEO, described stroke as to be considered a high-growth segment for the company.
He said that the company had entered the complete stroke care market, in which it did not participate before, through the $1.5 billion acquisition of the neurovascular business unit of Boston Scientific in 2010 followed by the acquisition of Concentric Medical (the maker of Merci Retriever and Trevo) in August 2011 for $135 million. He also said that the stroke care market is in its infancy and therefore long-term growth can be expected from it.
The Yahoo Finance website analysts valuations segment in August 2012 show for Covidien 18 buys and strong buys, two holds, with no sell recommendation, and for Stryker it shows 20 buys and strong buys, 11 holds and no sell.