October 01. 2012 9:00AM

New medical device prevents strokes

Innovations

By Erica Breunlin

  
When Greeta Cherayil Hoffbauer started feeling tired during a weekend getaway to Okauchee Lake in 2010, she hardly expected a stroke to be the culprit.
Zaidat

But when Dr. Thomas Connor, an ophthalmologist at Froedtert & The Medical College of Wisconsin who was among Hoffbauer's friends at the lake, noticed her speech slurring for no apparent reason and her eye reflexes abnormal, he suggested they head to the emergency room.

There at Oconomowoc Memorial Hospital, after confirmation of a stroke, the middle-aged Brookfield resident was administered a clot-busting drug. Once physicians determined a piece of the clot was blocking all blood flow to the brain through the basilar artery, however, they realized the clot would have to be removed.

Without the capabilities to do so at that hospital, they airlifted Hoffbauer, who was losing consciousness, to Froedtert.

"The last thing I remember was a nurse at Oconomowoc hospital saying to me, 'You're going on a helicopter ride,'" Hoffbauer said.

At Froedtert, Dr. Osama Zaidat, a neuro-interventionalist, operated on Hoffbauer without delay. Using the Solitaire Flow Restoration Device, a stent retriever designed and manufactured by Dublin, Ireland-based Covidien, Zaidat safely abstracted the clot by threading the device from the femoral artery near the groin all the way up to the brain.

Since Hoffbauer had been given clot-busting drugs, which thin blood, Zaidat had to be particularly careful during the surgical procedure. One accidental poke in the wrong place like a vein or artery could easily have resulted in her bleeding to death.

"Luckily for me he had a steady hand, and they got the clot out within 15 minutes of starting the procedure," Hoffbauer said.

"I think that's why I was not brain damaged – because they did it so quickly," she said.

The Solitaire device, approved by the U.S. Food and Drug Administration (FDA) in March of this year, has "a self-expanding, stent-like design," according to an article published in the medical journal Lancet in August. During a procedure, a physician admits it into a blocked artery with a small catheter tube. The device attaches to the clot and effectively traps it. According to Zaidat, the physician must hold the device steadily on the clot for at least five minutes "to engage the clot."

"That interaction between the device and the clot is what makes it efficacious," Zaidat said.

The physician then carefully retracts the device from the body with the clot attached, so that the affected blood vessel is reopened.

A typical procedure lasts between 45 minutes and an hour, Zaidat said.

The device was approved by the FDA after a 10-month clinical trial that ended almost a year earlier than planned at the recommendation of a safety monitoring committee. The premature ending came as a result of significant positive outcomes of the study.

Zaidat was one of the primary investigators in the Midwest during the study. Hoffbauer was a trial patient.

Zaidat also wrote a paper about the device that helped lead to its approval. The paper was published separately in Lancet in September.

Among the trial's most notable findings was the Solitaire stent retriever's success in performing without causing bleeding. It opened vessels blocked by clots without leading to symptomatic bleeding in or around the brain in 61 percent of patients, according to the August Lancet article. The previously approved mechanical tool used to remove stroke-causing blood clots, a corkscrew-like device known as the Merci Retriever, opened block vessels without subsequent bleeding in 24 percent of patients.

Within the study, Solitaire also produced a better survival rate three months after a stroke. While the Solitaire device had a 17.2 percent mortality rate, its predecessor had a 38.2 percent mortality rate.

Zaidat believes the effectiveness of the Solitaire device can largely be credited to its design. The design of the older devices used to remove clots made it more difficult for physicians to grab clots in their entirety, he said. The older devices also had substantial learning curves and were very operator dependent.

"It takes long to really master the technique and to tweak it for each operator to reach the desired effectiveness," Zaidat said. "There was variability in the results because of that."

As efficacious as the Solitaire device has been in removing stroke-causing blood clots, Covidien initially intended it to be a junctive device used in treating aneurisms. Covidien submitted the device as a tool to treat aneurisms to regulatory agencies in Europe before the United States. Researchers in Europe inadvertently realized its design could also address stroke-causing blood clots, and the device was tweaked to attend to clots.

Depending on how long a patient receives care after having a stroke, the Solitaire device can be administered in conjunction with clot-busting drugs. Drugs can assist in breaking up a clot up to 4.5 hours after a stroke patient has suffered the initial symptoms. After 4.5 hours has passed, it's best to turn immediately to the device.

Zaidat emphasizes the critical role time plays in recovering a stroke patient's deficit.

"The sooner you get to the hospital, the more likely you're going to have chances of reversing the stroke," he said.

Hoffbauer said she feels lucky that the device, the facilities and the expertise to remove her clot and reverse her stroke were all available to her immediately at Froedtert.

"Without Dr. Zaidat's expertise and the device to take out the clot, I could have had much worse outcomes – the worst being that I would not be alive," she said.
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