An arrhythmia is any disorder of your heart rate or rhythm. It means that your heart beats too quickly, too slowly or with an irregular pattern. When the heart beats faster than normal, it is called tachycardia. When the heart beats too slowly, it is called bradycardia.
Many factors can affect your heart's rhythm, such as having had a heart attack, blood chemistry imbalances or abnormal hormone levels. Some substances or medicines may also cause arrhythmias.
Sources
MedlinePlus - Arrhythmia
