Canadians who have an irregular heartbeat problem called atrial fibrillation are at least five times more likely to have a stroke, and twice as likely to die from one -- and most don't realize it, reports the Heart and Stroke Foundation.

Atrial fibrillation can cause the heart to beat very fast, sometimes more than 150 beats per minute. While it is rare in people under 40, its prevalence increases with age, as well as with other risk factors for heart disease and stroke including high blood pressure and diabetes.

The Heart and Stroke Foundation estimates that atrial fibrillation affects about 250,000 Canadians.

Up to 15 per cent of strokes are caused by atrial fibrillation, and in people over 60, that number increases to about one-third of strokes.

During atrial fibrillation, the upper chambers of the heart, known as the atria, contract chaotically and fail to move blood properly. That allows blood to pool in the heart, where clots can form. If those clots get pumped up to the brain, a stroke can result.

Heart and Stroke Foundation spokesperson and cardiologist Dr. Paul Dorian says that while blood thinner medications have been shown to be highly effective in managing atrial fibrillation, many Canadians are not being properly treated.

Warfarin, sold under the name Coumadin, is the most commonly prescribed medication for AF patients. An anticoagulant, warfarin prevents clots from forming in the heart and travelling to the brain. Yet its use in Canada by people over 65 with the condition remains below 50 per cent, says Heart and Stroke.

"Research does show us that a large proportion of patients with atrial fibrillation who should be on Coumadin to prevent stroke are not on Coumadin, and this is something that needs to be addressed," Dorian tells CTV News.

Dr. Marco Di Buono, director of research, Heart and Stroke Foundation of Ontario, says many doctors are still unaware of how dangerous atrial fibrillation is.

"Clinical guidelines are in place but there is a need for healthcare practitioners to be aware of the condition's risks and put the treatment options into practice," says Di Buono.

"Further, people with AF should talk to their healthcare providers about their stroke risk and what they can do about it."

The Heart and Stroke Foundation says a simple tool called the CHADS2 Index can help healthcare providers to determine a patient's stroke risk. One point is given for each risk condition. The higher the score, the greater the risk of developing stroke.

• Congestive heart failure - 1 point
• Hypertension (high blood pressure) - 1 point
• Age (greater than 75 years) - 1 point
• Diabetes - 1 point
• Stroke or transient ischemic attack (TIA) - 2 points

Anyone with high blood pressure is at increased risk of developing AF and should be aware of the symptoms:

• irregular and fast heartbeat,
• heart palpitations or a rapid thumping in the chest,
• chest discomfort, chest pain or pressure,
• shortness of breath, particularly with exertion,
• anxiety, fatigue, dizziness, sweating, nausea, lightheadedness or fainting

Canadians are also advised that healthy lifestyle changes that lower blood pressure, such as maintaining a normal weight and limiting salt intake and controlling diabetes, can help reduce the chances of developing atrial fibrillation.

Di Buono adds that Canadians -- AF patients especially -- should learn how to recognize and react to stroke warning signs. They include

• Weakness - Sudden loss of strength or sudden numbness in the face, arm or leg, even if temporary.
• Trouble speaking - Sudden difficulty speaking or understanding or sudden confusion, even if temporary.
• Vision problems - Sudden trouble with vision, even if temporary.
• Headache - Sudden severe and unusual headache.
• Dizziness - Sudden loss of balance, especially with any of the above signs

Stroke is a medical emergency - if you experience any of the signs of stroke call 9-1-1 or your local emergency number.