Arrhythmia, bradycardia, tachycardia

An arrhythmia is any change in the regular, even rhythm of the heartbeat. Most arrhythmias are harmless, but some can be serious and even life-threatening. Bradycardia is a slower than normal heart rate based on age and physical condition. Tachycardia is the medical term for a heart rate over 100 beats per minute. There are many heart rhythm disorders (arrhythmias) that can cause tachycardia.