Does Atrial Fibrillation Increase Stroke Risk?

A fellow caregiver asked...

If someone has atrial fibrillation and takes medication for it, is he still at increased risk for a stroke?

Expert Answer

Carolyn Strimike, N.P. and Margie Latrella, N.P. are cardiac nurse practitioners specializing in the prevention of heart disease and stroke. They have over 40 years of nursing experience in Cardiology between them. The main goal of their work is to counsel, motivate and empower women to adopt healthy lifestyle choices.

People with atrial fibrillation who take medication for their condition still have a slightly increased risk of stroke compared with people without this condition. But effective treatment can cut that risk by more than half.

The risk of stroke is not from the fibrillation itself, but from clotting. What happens is that blood can pool in the atria -- the upper chambers of the heart -- because the atria are fibrillating, or vibrating, instead of pumping effectively. And when blood pools, this increases the risk of clotting. So treatment focuses on preventing the blood from pooling.

Standard treatment is to thin the blood and prevent it from clotting. Medications used for this purpose are warfarin (Coumadin), an anticoagulant that prevents the blood from clotting; and aspirin, which thins the blood. Regular blood tests can show how well this treatment is working. If treatment is effective, ensuring that blood is being pumped completely out of the atria, then the risk of stroke shouldn't be seriously increased.

Additional treatment for atrial fibrillation focuses on reestablishing normal heart rate and rhythm, but it's important to understand that arrhythmia itself does not cause stroke. Medications are prescribed to slow down a rapid heart rate, and treatments such as electrical cardioversion and radiofrequency ablation are used to restore normal heart rhythm.

But it's the anticlotting treatment that prevents stroke, not the treatment for arrhythmia.