TORONTO - The vast majority of patients with narrowed carotid arteries but no warning signs of an impending stroke can avoid plaque-removing surgery and be treated instead with lifestyle changes and intensive drug therapy, researchers suggest.
In a study led by the University of Western Ontario, researchers found that 95 per cent of asymptomatic patients with even severely clogged carotid arteries would not benefit from surgery to clean out plaque or from insertion of a stent to open up the vessels.
Instead, such patients can be successfully treated to prevent a stroke with "intensive medical therapy," said principal investigator Dr. David Spence, director of UWO's Stroke Prevention and Atherosclerosis Research Centre.
"It's a whole package," Spence said from London, Ont., noting that the package includes eating a cardiovascular-friendly Mediterranean diet, quitting smoking and taking certain vitamins, blood pressure medication and the maximum dose of an anti-cholesterol drug.
Spence said the study of 469 patients with narrowed carotids but no other symptoms showed that intensive medical therapy dramatically reduced the number who had tiny clots - called microemboli - developing from the plaque and travelling to the brain. Larger clots can cause a stroke.
Symptoms that would signal an increased stroke risk include having previously experienced a mini-stroke (a transient ischemic attack, or TIA) or a full-blown stroke. TIAs typically last two to 30 minutes and may produce vision problems, dizziness, weakness or trouble speaking.
Before instituting the therapy at the London stroke clinic in 2003, 12.6 per cent of patients had microscopic clots travelling to the brain, which can be detected using a helmet-like ultrasound test. Since 2003, just 3.7 per cent of patients showed such clot activity.
As well, researchers found that the risk of stroke in the patients "went way down," to less than one per cent from four per cent. Heart attack risk in the first year went from 6.5 per cent to zero.
"What that means is that among patients with asymptomatic stenosis (clogging), the preferred treatment should be intensive medical therapy," said Spence, who presented the findings Thursday at the World Stroke Congress in Vienna.
He said using the ultrasound test - called Transcranial Doppler Embolus Detection - would help doctors determine which patients have microscopic clots and would thus benefit from the carotid-cleansing surgery or stenting.
That's important to determine because patients without the telltale clots have only a one per cent risk of suffering a debilitating or fatal stroke, while the chance of stroke or death related to the surgery or stenting runs as high as five per cent of patients.
"Since the risk of surgery is four to five per cent, patients without microemboli are better off with medical therapy, including medications and lifestyle modifications," Spence said. "Only the ones with microemboli would benefit from carotid endarterectomy or stenting."
An endarterectomy is the surgery to rid the carotid arteries of plaque buildup. The procedure involves making a small incision in the neck below the jaw to expose the artery. With blood flow diverted through a tube, the surgeon opens up the carotid to remove deposits. A stent is a hollow wire-mesh tube inserted into the artery and expanded to widen the vessel and improve blood flow.
Dr. Julia Hopyan of the regional stroke prevention clinic at Toronto's Sunnybrook Health Sciences Centre said the UWO-led study confirms "that we're on the right track in terms of stroke prevention strategies, including more aggressive cholesterol and blood pressure control, in the last few years."
However, she said further studies are needed to validate the results.
Hopyan, who was not involved in the research, believes Transcranial Doppler Embolus Detection is a test that should be more widely used by doctors.
"It's a very useful tool in helping to stratify these asymptomatic patients in terms of their stroke risk and advising for or against surgery," she said.
