Atrial fibrillation (AF) is an abnormal rhythm of the heart. The heart muscle cells contract (beats) and pumps the blood with a regular rhythm. During AF, the sinus rate 350 to 600 beats per minute, faster than the normal sinus rate (60 to 100 beats per minute). Fortunately, the AV node cannot conduct all of these impulses which results in blood pumping out with rapid or irregular (abnormal) rhythm. Atrial fibrillation is more common in men than women, who are more than 65 years of age. 

Types: there are three types

1. Lone atrial fibrillation (LAF)
2. Nonvalvular AF
3. Secondary AF