Atrial fibrillation (AF) is an abnormal fast irregular heartbeat. An abnormal heartbeat rhythm is called an arrhythmia. A normal heart rate is between 60 and 100 beats a minute (bpm) when you're resting. In AF the heart rate can sometimes be very fast (often between 140 and 180 bpm) as well as being irregular.

What does FAST AF mean?

In atrial fibrillation, the heart's upper chambers (atria) contract randomly and sometimes so fast that the heart muscle cannot relax properly between contractions. This reduces the heart's efficiency and performance. Atrial fibrillation happens when abnormal electrical impulses suddenly start firing in the atria.

What rate is fast AF?

AF is most commonly associated with a ventricular rate ~ 110 – 160. AF is often described as having 'rapid ventricular response' once the ventricular rate is > 100 bpm. 'Slow' AF is a term often used to describe AF with a ventricular rate < 60 bpm.