Canadian researchers close in on ‘silent killer’
Study finds new medical options for stroke victims
Canadian researchers, in the world’s largest heart monitoring study of stroke patients, have found a novel way to better detect abnormal and erratic heart rhythms in stroke survivors that increase their risk for a second and potentially lethal brain attack.
Published this week in the New England Journal of Medicine, the finding is expected to change the standard of care for thousands of Canadians who suffer unexplained strokes every year.
The 16-centre study found that a new strategy involving continuous, 30-day heart monitoring finds five times as many cases of atrial fibrillation than the standard 24hour test.
With atrial fibrillation, or AF, the heart quivers and beats chaotically. Blood can pool in the upper left chamber of the heart, allowing clots to form and travel through the circulation into the brain.
People with AF have a stroke risk three to five times higher than those without the heart condition, and their strokes are often more devastating and deadly than strokes due to other causes: 70 to 80 per cent of people who suffer an AF-related stroke die or become disabled. Some result in “instantaneous dementia,” researchers say.
“These are often tragic strokes that can impair memory, language and other cognitive functions and result in permanent disability,” said the study’s lead author, Dr. David Gladstone, an associate professor in the department of medicine at the University of Toronto.
“We want to do the utmost to improve stroke prevention, and one way to do that is by early detection and treatment of atrial fibrillation.”
Yet AF is often “silent,” making it notoriously difficult to detect. Unless people experience telltale symptoms such as fluttering of the heart, skipped heartbeats or shortness of breath, the condition is often missed.
“We regularly see patients with warning strokes or transient ischemic attacks — mini strokes — for which there is no obvious cause found,” said Gladstone, director of the Regional Stroke Prevention Clinic at Toronto’s Sunnybrook Health Sciences Centre. “Patients undergo all the standard diagnostic tests and they all come back ‘normal.’ The underlying cause of the stroke remains a mystery.”
The standard treatment for these so-called “cryptogenic” strokes is usually low-dose Aspirin to prevent a second stroke.
“But if the person has AF that might not be strong enough,” Gladstone said. Stronger anti-clotting drugs can lower the risk of a second stroke by half or more.
The new study involved 572 patients aged 55 and older, and without known AF. All underwent conventional 24-hour monitoring that didn’t reveal AF.
Next, the patients were randomized into two groups: One received an additional 24 hours of the usual monitoring using a small device that clips on a belt with wires taped to the torso; the other received prolonged monitoring using an electrode belt worn around the chest. Patients were asked to wear the monitor as much as possible for 30 consecutive days.
AF was detected in 16 per cent of the patients in the 30-day group versus three per cent in the 24hour group. As a result, nearly twice as many patients could be switched to stronger medications.