Can you do too much to prevent a stroke?
Personal Health: Too many people who are free of symptoms associated with stroke are undergoing surgery to clear carotid arteries, or are having stents inserted, than is justified by available evidence, experts say.
The New York Times
Stroke is the fourth-leading cause of death among Americans, and a much larger contributor to chronic disability and health care costs than this ranking suggests. There's no question that preventing strokes is important. But a big question is how best to do so and in whom.
Currently, some experts say, far too many people who are free of symptoms that might herald a stroke are undergoing surgery to ream out carotid arteries that feed the brain, or are having stents inserted in these arteries, than is justified by available evidence.
Critics say these invasive procedures on asymptomatic patients are unnecessary, creating a risk of serious complications like heart attack or, ironically, stroke itself, even death, and driving up health care costs.
Based on the latest research, they maintain, most patients without symptoms like a mild stroke or transient ischemic attack do as well — or nearly as well — with intensive medical therapy to control blood pressure, cholesterol and diabetes.
"Intensive medical therapy is a much safer way to prevent strokes caused by clots than either surgery or stenting," said Dr. David Spence, a stroke prevention specialist at the University of Western Ontario.
But surgeons, even those who acknowledge the limits of current research, nonetheless say carotid endarterectomy, as the reaming operation is called, is the treatment of choice for many patients with serious blockages. That sentiment also is reflected in guidelines from the Society of Vascular Surgeons and the American Heart Association.
Dr. Michael Belkin, the chief of vascular and endovascular surgery at Brigham and Women's Hospital in Boston, who performs scores of endarterectomies each year, said, "In asymptomatic patients with high-grade carotid stenosis, meaning a blockage of 70 percent or greater, surgical therapy is better than medical therapy."
But he emphasized that good surgical results depend on selecting patients who have at least a five-year life expectancy and are healthy enough to tolerate the operation. He also said the procedure should be done only by a surgeon with a good track record and lots of experience.
"This is an elective procedure," Belkin said. "Patients should be well-informed about the benefits and risks."
To stent or not
Experts are less sanguine about inserting stents in asymptomatic patients. They said pressure was being exerted by stent manufacturers, who would like to see them used as widely as possible. Stents, which are threaded through a catheter from the groin to the carotid arteries in the neck, are used to keep an artery open after a balloon presses the plaque against the artery's walls.
"Stents are pretty good, but not as good as surgery for asymptomatic disease," Belkin said.
Still, many cardiologists who insert stents into coronary arteries to prevent heart attacks are now stenting partly blocked carotids in hopes of preventing strokes in patients otherwise free of symptoms.
Dr. Frank J. Veith, a vascular surgeon affiliated with New York University, called carotid stenting in asymptomatic patients by interventional cardiologists "a moneymaking free-for-all" that doesn't take into account vital differences between arteries to the heart and those to the brain, which has more vessels feeding it.
Spence said, "Cardiologists have no business messing with carotid arteries."
There is "a natural bypass called the Circle of Willis at the base of the brain to which all four arteries that feed the brain are connected," he said. "If one artery is blocked, blood gets to the brain through the other three."
Despite pleas from interventional cardiologists, Medicare has thus far declined to cover the costs of carotid stents in low-risk patients without better evidence of their benefit.
Complicating the issue is that only about one-quarter of strokes result from carotid disease. The rest are caused by problems like clots coming from the heart and ruptured blood vessels in the brain. So treating carotid arteries surgically or with stents is no guarantee against a stroke.
Another problem is identifying patients without symptoms of carotid disease who do face a high stroke risk, Veith said. About 50 of his patients with severe carotid disease have been free of strokes for years, he said.
Ultrasound is most often used to screen for carotid disease, which may also be suggested by a whooshing sound in the neck, called a bruit, heard through a stethoscope.
Reducing the risks
No one questions that surgery or stenting is advisable for patients with symptoms if they are healthy enough to undergo the procedure. But for patients who lack symptoms, all sides agree that a trial comparing the benefits and risks of surgery, stenting and modern medical therapy is sorely needed.
Until that study is done, the controversy will continue over how to best treat carotid disease in patients without symptoms.
For example, Harvard Medical School experts recently stated that before carotid surgery or stenting is recommended, doctors should consider that "medical treatment is preferred for symptomatic patients with mild narrowing and also for many asymptomatic patients with moderate or even severe narrowing. And even patients who undergo artery-opening procedures need long-term medical therapy."
Spence, noting that the main study used to justify invasive treatment, called ACAS, enrolled patients in 1995, said, "Interventionists are using old data to justify procedures now not warranted because the risk of stroke in asymptomatic patients has changed dramatically since then."
These reductions in stroke risk, he said, are from better drugs to treat high blood pressure, lower cholesterol and prevent clots; stopping smoking; and improved control of blood sugar in people with diabetes.
Veith said statin therapy is primarily responsible for reducing the risk of stroke in asymptomatic patients to a level equivalent to the benefits of surgery or stenting. Statins are mainly used to lower artery-damaging cholesterol, but the drugs also stabilize arterial plaque, preventing pieces from breaking off and blocking small blood vessels in the brain, where they would cause a stroke.
Spence is a strong advocate of a traditional Mediterranean diet, high in whole grains, fruits and vegetables, lentils and beans, olive oil and canola oil and low in cholesterol and animal fats.
"I recommend that my patients go vegetarian every other day," he said, "and when they eat meat, chicken or fish on the days in between, the portion should be the size of the palm of their hand."
Information in this article, originally published Oct. 16, 2012, was corrected Oct. 16, 2012. A previous version of this story misidentified the main study used to justify invasive treatment of blockages in the carotid arteries to prevent stroke in people who have no symptoms. The study is known as the ACAS trial, not the CREST trial.