Tachycardia & Bradycardia are the two very basic forms of Arrhythmia. Tachycardia is the medical condition in which the heart rate is faster than normal. The heart rate in the upper chambers or lower chambers of the heart, or both is increases.
In bradycardia the heart rate is slower than normal. The condition can be serious if the heart fails to pump enough oxygen-rich blood to the body.