Heart disease - atrial fibrillation

Atrial fibrillation 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% of the population over the age of 45 and 6% 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 and 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 3 to 5 times greater risk for stroke than those without AF.

Atrial fibrillation and stroke

AF increases your risk of stroke and it is estimated that up to 15% of all strokes are due to atrial fibrillation. This risk increases with age, so that after age 60, one-third of strokes are due to AF. It is estimated that individuals with atrial fibrillation have 3 to 5 times greater risk for ischemic stroke (see here for more information).

Here’s what can happen: Normally the heart receives electrical signals from the brain via the sinoatrial (SA) node, which regulates heart rhythm. The SA node sends impulses through the atria to tell them to beat. The impulses then makes 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. Instead of beating normally and efficiently, the atria quiver. Because the atria don’t move blood properly, blood pools and gets stuck in the grooves of the heart. Clots can form from this pooled blood, which may finally get pumped up to the brain and result in a stroke. An ischemic stroke is caused when blood flow to the brain is interrupted by a clot in one of the blood vessels leading to or in 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%

For more information on atrial fibrillation.

Last reviewed February 2009.