Longer heart monitoring can detect more A-fib, major cause of stroke: researchers

TORONTO - A heart-rhythm disorder called atrial fibrillation is on the rise among older Canadians, but standard testing often doesn't detect the condition, leaving patients untreated and prone to potentially disabling or fatal strokes.

Among those who have had a stroke, standard testing includes wearing a portable electrocardiogram for 24 hours to check for episodes of an irregular heartbeat. But often the heart monitor will turn up no anomalies, so doctors are unable to come up with a specific diagnosis.

"Atrial fibrillation can be notoriously difficult to diagnose because it is often silent and comes and goes intermittently, so it can be a hidden risk factor for stroke," said Dr. David Gladstone, director of the stroke prevention clinic at Sunnybrook Health Sciences Centre.

"Strokes related to atrial fibrillation are often devastating, causing long-term disability, dementia and death," Gladstone said Wednesday. "They tend to be more severe and disabling and deadly than strokes due to other causes."

The Toronto neurologist is principal investigator of the EMBRACE trial, one of two major studies published Thursday in the New England Journal of Medicine that found a more successful method of detecting the disorder.

Simply put, the two teams kept patients on heart monitors longer — for 30 days in the Sunnybrook-led Canadian trial, using a wearable device, and up to three years with an implantable monitor for patients in the CRYSTAL AF study, a collaboration among European, U.S. and Canadian researchers.

Gladstone's team, which included more than 50 researchers across the country, looked at 572 patients who had suffered an unexplained stroke or TIA (transient ischemic attack), half of whom were randomly assigned to wear a heart monitor for 24 hours, while the other half were kept on the device for 30 days.

"We found a five-fold increase in the detection of silent atrial fibrillation compared to the standard method," he said. Among patients in the 24-hour ECG group, three per cent were found to have atrial fibrillation, while the month-long monitoring turned up 16 per cent of participants with the fluttery-heart disorder.

In the CRYSTAL AF trial of 441 patients who had experienced a stroke with an unknown cause, the heart rhythm disorder had been detected after six months in nine per cent of patients with an implanted heart monitor, compared to two per cent in the control group. At 12 months, A-fib was found in more than 12 per cent of patients with the implanted monitor, versus two per cent in the other group.

"One in every four strokes is of unknown cause," said Gladstone. "So it has remained a mystery for years, and this research is helping to give us a better understanding about cryptogenic stroke (of unknown origin) and it suggests that atrial fibrillation may be a much more common risk factor than previously appreciated."

Stroke is the second leading cause of death worldwide, and in Canada someone has a stroke every 10 minutes, he pointed out.

"We've got to change those statistics. And one way to do that is through early detection of atrial fibrillation, which is one of the most treatable risk factors for stroke."

The disorder occurs in the upper left chamber of the heart and causes the heart to beat quickly or with an irregular pattern. That means the blood doesn't get pumped properly — and that can lead to a clot forming, which may travel to the brain, block an artery and result in a potentially neuron-destroying stroke.

Patients are treated with an anticoagulant, or blood-thinning, medication such as warfarin, which stops the formation of clots and prevents recurrent strokes.

Gladstone said the results of the EMBRACE trial have already led Sunnybrook's stroke clinic to begin changing practice by providing some patients with advanced heart-monitoring devices to wear for a prolonged period.

One of those patients is Bedros (Peter) Kashkarian, who experienced a TIA in February while in his north Toronto food store. Kashkarian, 67, had been running up and down the stairs in the store, when he tried to speak to a visiting friend.

"I was calling his name ... and then I couldn't," he said. "My speech was mumbling. It happened three times, around a minute."

His family doctor referred him to Sunnybrook, where Gladstone told the grocer he suspected he'd had a mini stroke and ordered tests.

"Everything was negative, negative, negative," Kashkarian said. "And then he put me on a monitor for two days and nothing showed, everything was good.

"The amazing thing is that Dr. Gladstone, he wanted to pinpoint (the cause) ... He wasn't satisfied ... He wanted to find out exactly, which is good."

Kashkarian was hooked up to a wireless heart monitor for two weeks — and sure enough, the device recorded a 15-hour period when his heartbeat went awry, showing he indeed had atrial fibrillation.

Now on twice-daily blood-thinner medication, Kashkarian said he feels great.

"It's like prevention, which is good. We caught it in time."

Gladstone said the next phase of the research will use advanced heart-monitoring devices in elderly people who have not had a stroke to test for A-fib.

"Ultimately we want to detect and treat atrial fibrillation before it ever leads to a stroke," he said. "And the hope is that strokes and deaths can be prevented."

In an accompanying editorial, stroke specialist Dr. Hooman Kamel of Weill Cornell Medical College in New York writes that the two patient trials show that extended heart monitoring identifies atrial fibrillation that would have otherwise gone undetected.

"The results of two studies published in this issue of the journal indicate that prolonged monitoring of heart rhythm should now become part of the standard care of patients with cryptogenic stroke."

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