Arrhythmia is an abnormal rhythm or rate of heart beat and is caused by a disturbance in the electrical nerve impulses of the heart. Tachycardia is where the rate is faster than 100 beats per minute, and bradycardias is where the rate is slower than 60 beats per minute.

In atrial flutter, the beat rate is 200 to 400 bests per minute, but not every impulse reaches the ventricles. A totally uncoordinated beating of the heart at about 300 to 500 beats per minute is called atrial fibrillation.

The most common cause of arrhythmia is arteriosclerosis where deposits narrow the blood vessels and inadequate blood supply reaches the heart muscle. Arrhythmias occur more frequently after a heart attack.

Caffeine and other drugs can also cause tachycardia. and Certain antidepressant drugs can cause serious cardiac arrhythmias if taken in high doses.