Study participant Bob Luck, left, and research assistant Haris Vaid while testing a Braemar cardiac event monitor and electrode belt at Toronto’s Sunnybrook hospital, Feb. 5, 2013.Fernando Morales/The Globe and Mail
Canadian researchers believe they have found a better way of identifying patients who have an irregular heartbeat, which is a leading cause of strokes. And the key is new technology – a wearable device that allows patients to be monitored for prolonged periods.
Known medically as atrial fibrillation, an irregular heartbeat is one of the most treatable risk factors for strokes. The condition causes blood to pool temporarily in the heart, potentially leading to the formation of clots that can travel to the brain and block blood flow to part of the vital organ.
Patients diagnosed with atrial fibrillation are usually prescribed powerful blood-thinning medications that dramatically reduce their chances of a clot lodging in the brain. The problem, however, is that atrial fibrillation can often be extremely difficult to detect. In some patients the irregular beat may last for just a few minutes before reverting to its regular rhythm.
Under current medical practices, high-risk individuals – those who have already suffered a stroke or a transient ischemic attack (TIA or mini-stroke) – will wear an electronic heart monitor for 24 hours. But the new study, presented Thursday in Hawaii at a scientific meeting of the American Stroke Association, suggests one day may not be enough time to identify all cases of atrial fibrillation.
"The harder we look, the greater the chance of finding this hidden risk factor – it's like medical detective work," explained the lead researcher, Dr. David Gladstone, director of the Regional Stroke Prevention Clinic at Sunnybrook Health Sciences Centre and an associate professor in the Department of Medicine at the University of Toronto.
The trial involved 572 patients who recently suffered a stroke or TIA but the underlying cause of the clot had not been identified. In particular, they didn't have the normal risk factors for stroke, such as plaque build-up in their arteries. What's more, the standard heart monitor test failed to find atrial fibrillation.
For the study, one group of participants was given a 24-hour heart-monitor test. The other group received 30 days of continuous assessment using new technology that permits long-term monitoring at home.
The study revealed that 30-day monitoring detected atrial fibrillation in 16 per cent of patients. By contrast, the 24-hour test picked up an irregular heart beat in just 3 per cent of those studied.
"That means one in six patients who underwent 30 days of monitoring were found to have a new diagnosis of atrial fibrillation that otherwise would have gone undetected and it resulted in a significant increase in patients receiving treatment with stronger anti-clotting medications for stroke prevention," said Gladstone.
"This study provides the strongest evidence to date for supporting a prolonged heart-monitoring strategy," he added.
Of course, a longer monitoring period will be more expensive than a one-day test. The high-tech monitors alone cost hundreds of dollars each. But Gladstone believes the increased cost of testing could be more than offset by reducing the number of people who experience catastrophic strokes.
"With early detection and treatment, we hope that more strokes and deaths can be prevented," he said. Atrial fibrillation is often responsible for causing the most severe strokes, which are associated with greater cost to the health-care system in terms of long hospital stays, nursing-home admissions and treating the resulting disabilities.
He noted that an estimated three million people worldwide each year suffer from a stroke of unknown cause. Based on the findings from his study, half a million of these patients could have untreated atrial fibrillation. Even so, this doesn't mean that the entire adult population should be screened for atrial fibrillation using high-tech 30-day monitors. This type of costly testing should be reserved for patients deemed at high risk – and that usually means elderly people who have already had one stroke or those troubled by frequent TIAs without a clear cause.
"A third of the patients in our study had TIAs – and those are ideal candidates for aggressive diagnostic investigation because you want to prevent the big stroke that could happen next."
The $1.5-million Canadian study involved researchers and patients at 16 stroke centres across the country. It was funded by the Canadian Stroke Network and co-ordinated through the Li Ka Shing Knowledge Institute of St. Michael's Hospital in Toronto.