The risk of stroke due to atrial fibrillationgoes up with age. Those in their 50s who don't take blood thinners have about a 1.3 percent chance of stroke every year. The risk goes up to about 5 percent per year for those in their 80s who have atrial fibrillation and don't take blood thinners.
To further personalize the risk of stroke from atrial fibrillation, doctors often use a risk calculator called CHADS2. This calculator assigns a point for each of the following:
- Heart failure
- High blood pressure
- An age of 75 or older
- A history of stroke or TIA ("transient ischemic attack", also known as "ministroke") (this causes a two-point rise)
For those with none of the above conditions and not using blood thinners, the risk of A-fib-related stroke is about 0.5 percent per year. For those with all the above conditions, the risk of stroke is about 6.9 percent per year.
Based on the point score, the risk of A-fib-related stroke in those not using blood thinners ranges from 0.5 percent per year (for those with none of the above conditions) to 6.9 percent per year (for those with all of the above conditions).
Using a strong blood thinner such as warfarin or dabigatran reduces the chance of stroke by about half.