Brain-Specific Stent Shows Promise in Preventing Strokes

A new stent designed for placement deep inside the narrow arteries of the brain has proved safe in holding blocked blood vessels open and reducing stroke survivors' risk of having another stroke, according to a study presented by Osama O. (Sam) Zaidat, MD, MSc, Medical College of Wisconsin Associate Professor of Neurology and Neurosurgery and Director of the MCW Neuro-Interventional Program.

Like stents commonly used to treat clogged arteries in the heart and leg, the "Wingspan" stent is a tiny tube used to prop open the area of blockage. But this stent is even thinner and far more flexible than the others, made of a metal alloy mesh with enough "give" to navigate the tricky fragility of brain arteries.

"When we used this newly-designed brain stent across the country in 16 major US institutions, we had a very good safety profile," said Dr. Zaidat. "That's the key finding of our study. Prior to this stent, the safety and complication rate using stents in the brain was not very good and were not very acceptable to patients or referring physicians. When we placed a stent that was not specifically designed for the brain we had to deal with a lot of technical and procedure-related issues, which have been associated in the past with a high morbidity."

The Wingspan stent is used to treat patients who have had ischemic strokes, the kind of stroke caused by a clot or other blockage in a brain artery that inhibits blood flow. Ischemic strokes are the most common type of stroke, leaving tens of thousands of patients in the US with brain damage - or killing them - each year.

Reducing Complications and Risk
Dr. Zaidat presented the Wingspan study findings at the 2007 International Stroke Conference. The study was completed in November 2006 using data from the first year after FDA approval of the stent. Before the new stent was developed, said Dr. Zaidat, attempts to deploy stents in the brain did not show good results in great part because the relatively cumbersome stents made for other parts of the body could not be accurately positioned in the brain.

Using a technique similar to other stenting procedures but refined to accommodate the physical characteristics and location of brain arteries, the Wingspan stent is "packaged/housed" within a tiny and flexible long brain catheter. The catheter is maneuvered to just the right point past the blockage, where it is pulled back to unsheath and open the stent to be deployed. The blocked area is usually pre-dilated (angioplasty) with small, specifically-designed brain balloon.

"This study shows that the newly-designed "Wingspan" stent can be placed safely with a procedure risk (for complication) of less than five percent," said Dr. Zaidat. "The 161 patients enrolled had a success rate with this stent of 95.4%, which is quite an increase in the safety as compared to the old technique and the old devices that we were using before. The risk of complication using stents that are not specifically designed for the brain can be as high as 50%."

"And, a patient with a stroke related to a blocked or narrowed artery inside the head had a very high risk of subsequent strokes despite the use of the best medical therapy available at this point (such as aspirin and blood-thinning drugs). So if you give a patient with a blocked artery in the head the best medical therapy that's out there, and they have more than 70% blockage, the risk of subsequent stroke can be up to 35% over a two-year period."

Stroke, Brain Bleed and Death
Finding ways to reduce the risk of subsequent stroke is the overall goal of the research, said Dr. Zaidat. In general terms, he said, it can be expected that 18% of ischemic stroke patients who receive only traditional drug therapy will experience another stroke or brain bleed or death within three months. According to data from the safety trials of the Wingspan stent, that number was just 12% for patients with the stent in place.

The new brain stenting technique is mostly performed by neuro-interventionalists (who are already fellowship-trained specialists in catheterizing and performing procedures on brain arteries) who must perform two such procedures under supervision before they are allowed to "go solo," said Dr. Zaidat. He is one of the proctors who travel the country training and assisting other neuro-interventionalists in use of the Wingspan device.

The next phase of study will specifically compare outcomes from brain stenting to those from optimal drug therapy in a major research effort led by academic and university centers across United States. Dr. Zaidat said he expects the need for 600 to 900 patients enrolled through about 40 medical centers nationwide to complete the future study.

"For example, and we certainly don't know this to be true yet, if this stent is proven in future studies to have a 15% risk of subsequent stroke within two years, that would be a dramatic improvement from the 35% risk with optimal medications," said Dr. Zaidat. "The risk with this disease is quite high, so it's clear that we need to do something besides the current medical therapy to try and bring that risk down."

Dan Ullrich
HealthLink Contributing Writer

For more information on this topic, see the HealthLink article Stenting Techniques and Outcomes Vary.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.