A heartbeat can become irregular at any heart rate, which is the number of times the heart beats in a minute, ranging from 50 to 100 bpm; in normal conditions, it should be between 60 to 75 bpm. Arrhythmia can occur at slow heart rates, i.e. less than 60 bpm, or at high heart rates, i.e. more than 100 bpm. The former is called bradyarrhythmia or bradycardia, while the latter is known as tachyarrhythmia or tachycardia.