Heart disease - atrial fibrillation

Atrial fibrillation (AF) is a condition involving an irregular heart rhythm, known as an arrhythmia. It is the most common type of arrhythmia, affecting approximately 250,000 Canadians. While it is rare in people under 40, its prevalence increases with age. About 3 per cent of the population over the age of 45, and 6 per cent over age 65, have atrial fibrillation. After the age of 55, the incidence of AF doubles with each decade of life.

Generally the risk of developing AF increases with age and with other risk factors such as diabetes, high blood pressure, and underlying heart disease. One of the main complications of atrial fibrillation is that it may result in a stroke. Individuals with atrial fibrillation have a 3 to 5 times greater risk for stroke than those without AF.

Atrial fibrillation and stroke

AF increases your risk of stroke. It is estimated that up to 15 per cent of all strokes are caused by atrial fibrillation. This risk increases with age, so that after age 60, one-third of all strokes are caused by atrial fibrillation. Also, individuals with atrial fibrillation have 3 to 5 times greater risk for ischemic stroke.

With a normal heart rhythm, the heart receives electrical signals from the brain via the sinoatrial (SA) node. The SA node sends impulses to the atria which instructs them to beat. The impulses then make their way to the lower chambers of the heart (the ventricles), which pump blood to the rest of the body.

During atrial fibrillation, the atria contract chaotically and in a disorganized manner. Because the atria don’t move blood properly, blood pools and gets stuck in the grooves of the heart. This may result in the formation of blood clots, which could get pumped to the brain and result in an ischemic stroke. An ischemic stroke is caused when blood flow to the brain is interrupted by a clot in one of the blood vessels within, or leading to, the brain. Studies show that long-term use of the blood thinner warfarin in patients with AF can reduce the risk of stroke by 70 to 80 per cent.

For more information on atrial fibrillation.

Last reviewed February 2009.