What are abnormal heart rhythms called?

Arrhythmia: An irregular heartbeat is an arrhythmia or also know as dysrhythmia.

Arrythmias: This term is often used to describe heart rhythms different from a normal sinus rhythm.

An arrhythmia: Abnormal heart rhythms (arrhythmias) are caused by problems with the electrical system that regulates the steady, rhythmic beat of the heart. The heartbeat may be too slow (bradycardia) or too fast (tachycardia); it may remain steady or become chaotic. Some arrhythmias are dangerous and cause sudden cardiac death, while others may be bothersome but are not life threatening. See PCP ASAP.