Irregular heart rhythm a major clue to unexplained strokes, Canadian study finds

30-day home-based monitoring key to detection of hidden risk factor

HONOLULU, Hawaii, February 7, 2013 /Canada NewsWire/ - A significant portion of people with unexplained strokes has silent atrial fibrillation, researchers in 16 Canadian stroke centres discovered as part of the largest study and first randomized clinical trial of heart monitoring in stroke patients. Atrial fibrillation, an irregular heart rhythm, is known to cause some of the most disabling, deadliest, and most costly types of strokes, but it can be a silent risk factor that evades detection.

The three-year EMBRACE trial involving 572 patients was presented today at the International Stroke Conference by lead researcher Dr. David Gladstone of the University of Toronto Department of Medicine. He reported that with a new strategy of advanced heart monitoring, one in six people with an unexplained stroke or transient ischemic attack (TIA) were found to have silent atrial fibrillation that would have otherwise gone undiagnosed and untreated by standard methods.

"This study provides the strongest evidence to date to support intensive heart monitoring in patients with unexplained strokes or mini-strokes," according to the American Stroke Association, which highlighted the Canadian research as a late-breaking research development at the meeting.

Atrial fibrillation is a risk factor for stroke because it can promote the formation of blood clots in the heart that can travel to the brain. It is important to detect because it can be effectively treated with certain anti-clotting medications, which cut the risk of clots and strokes by two-thirds or more.

Dr. Gladstone, based at Toronto's Sunnybrook Research Institute and Sunnybrook Health Sciences Centre, said the Canadian Stroke Network-funded study has implications for improving stroke prevention.

"The hope is that earlier detection and treatment of atrial fibrillation may lead to more strokes prevented and more lives saved."

The challenge has been that atrial fibrillation is often hard to detect because the irregular heartbeat may last for just a few minutes at a time, after which the heart reverts back to its normal rhythm. Unless an individual is wearing a heart monitor at the time it occurs, the diagnosis is usually missed. In practice, stroke patients have traditionally received short-duration heart monitoring for 24 or 48 hours to screen for atrial fibrillation. However, advances in heart monitoring technology now make it possible for patients to be screened at home for much longer periods.

The trial studied patients who had a recent stroke or mini-stroke of unknown cause and in whom standard heart monitoring failed to detect atrial fibrillation. Participants were randomized into two groups: the first received an additional 24 hours of monitoring, and the second received continuous monitoring for 30 days at home using a new technology chest electrode belt that automatically detects episodes of atrial fibrillation.

In the study, prolonged monitoring picked up a new diagnosis of atrial fibrillation in 16 per cent of patients, compared to three per cent of those who only received an additional 24 hours of monitoring. The enhanced detection led to significantly more patients being prescribed stronger anti-clotting medications to prevent recurrent strokes.

This research is relevant to an estimated three million people worldwide every year who suffer strokes of unknown cause. It will force experts to rethink the diagnostic and treatment approaches for such patients with so-called 'cryptogenic' strokes, which have remained a medical conundrum for years. The implication is that a half-million stroke patients each year may have untreated atrial fibrillation and not know it.

"These results are practice-changing," says Dr. Antoine Hakim, CEO and Scientific Director of the Canadian Stroke Network. "This study really shows that the harder you look, the more atrial fibrillation you will find."

The Canadian Stroke Network ( is a national research network headquartered at the University of Ottawa. It includes scientists, clinicians and health-policy experts committed to reducing the impact of stroke.