Atrial fibrillation, commonly known as Afib or AF, is an irregular heartbeat caused by an abnormal heart rhythm that makes the upper heart chambers (the atria) quiver. While Afib itself generally is not life-threatening, the complications from Afib can be very serious. Afib can increase the risk for heart problems, including heart failure, as well as the risk for stroke. To understand Afib, including how it can be treated, it helps to learn how the heart functions normally. In this center, you'll learn about how the heart works, risk factors for atrial fibrillation as well as how Afib is diagnosed and can be treated.