Stents showing promise for prevention of strokes

MEDICAL MATTERS

May 19, 2006|By JUDY FOREMAN

Stents, long famous for their success in propping open clogged arteries near the heart, are being used in neck arteries in an effort to reduce strokes, and the technique is highly promising.

So promising, in fact, that some experts fear that doctors may adopt the procedure - and patients may clamor for it - before there is enough research to support it.

With carotid stenting, doctors insert a mesh device into a clogged carotid artery in the neck to keep blood flowing to the brain. The stents can be placed in the carotid arteries without general anesthesia.

"The procedure is less invasive and recovery is faster than with endarterectomy," the traditional, surgical approach to fixing narrowed arteries, said Dr. Marc Mayberg, executive director of the Seattle Neuroscience Institute, a neurological disease research center.

But he said he worries that carotid stenting "may be over-applied in patients who actually don't need it, who don't need any treatment at all or who would do well on medications alone."

He added, "There is little scientific data yet to show that stents are an effective way to prevent strokes, while there is such data for endarterectomy," which involves cutting open the arteries and scraping out fatty debris. Every year, about 150,000 Americans undergo this procedure.

"Like any new procedure, stenting needs to be validated through scientific testing, and that scientific testing is simply not available yet," he said.

On the other hand, the new procedure has a growing number of advocates. Carotid stenting is clearly "the coming thing," said Dr. Barry T. Katzen, medical director of the Baptist Cardiac and Vascular Institute in Miami. "We are very excited about this technology."

"We now have equipment that is much smaller, much more elegant," making the procedure easier and safer, said Dr. Piotr Sobieszczyk, a cardiologist at Brigham and Women's Hospital in Boston. "In the future this may well be the preferred way of treating carotid artery blockages."

Although carotid stenting has been around since the early 1990s, it is taking off now because engineers have added filters to the stents to catch debris that can be knocked off during insertion of the stent.

Unlike experimental stents, which had no filtering devices, the new carotid stents are passed over wires that have little traps on the tip to catch this debris, which could otherwise travel to the brain and cause strokes - the thing doctors are trying to prevent. At the end of the procedure, this filter wire, with the debris inside, is withdrawn. The addition of the filtering devices has been "crucial to the rapid development of this procedure," Sobieszczyk said.

Stenting got another boost last year when Medicare agreed to pay for the procedure in certain patients.

Despite its promise, stenting will probably not be the first choice for many people at risk of stroke.

While some strokes occur because of bleeding in or near the brain, most are ischemic strokes that occur when blood supply to the brain is blocked by a blood clot or bits of fatty plaque that have broken off from artery walls. A small percentage of ischemic strokes are caused by the build-up of plaque in artery walls - carotid stents are designed to prevent these.

While there is not as much data on stenting as on surgery to prevent strokes, a major study called SAPPHIRE, published in 2004, did show that carotid stents were just as effective at reducing strokes as endarterectomy and were linked to fewer heart attacks during the procedure.

There are risks to both procedures. The risks of endarterectomy include infection and injury to nerves in the neck. The risks of stenting include heart rhythm disturbances caused by dilation of the carotid artery, which in turn affects the vagus nerve, which influences cardiac rhythms. On the plus side, there is preliminary evidence that carotid stenting may improve cognitive function, said Dr. Rod Raabe, an interventional radiologist at the Sacred Heart Medical Center in Spokane, Wash.

A study Raabe presented in March at the annual meeting of the Society of Interventional Radiology showed a statistically significant improvement in memory and other cognitive skills after stenting, even in patients who had been deemed asymptomatic, or who had not had strokes.

But the big outstanding question is this: Should stenting be used for people at moderate risk of stroke who have no overt symptoms such as TIAs, or transient ischemic attacks, also known as mini-strokes? That issue is being addressed in a study called CREST funded by the National Institutes of Health, which is still open to new patients.

Until that study is finished, the prudent course - if you are at risk for stroke because of high blood pressure, smoking, clogged carotid arteries or other risk factors - is to talk with your doctor and try medications first to reduce your risk. If these don't work and you need something more invasive to keep your carotid arteries open, carefully weigh the pros and cons of endarterectomy and stents. Ask how much training the doctor has had in these procedures. And don't be afraid to get a second opinion.

Send your questions to foreman@baltsun.com.

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