Arrhythmia (uh-RITH-mee-uh) is a condition in which the heartbeats are irregular, too slow, or too fast. If the heart rate is over 100 beats per minute, it's called tachycardia (tak-ee-CARD-ee-ah).

Your heart beats according to a specific patterned flow of electrical impulses. An abnormally slow or fast pattern can generally be detected by any one of several tests that study this electrical flow.

Premature heartbeats are a form of cardiac arrhythmia (uh-RITH-mee-uh), or heartbeat rhythm irregularity. There are two kinds of premature heartbeat conditions, both of which are caused by mistiming of the electrical signals sent through the heart muscle.