An arrhythmia is a recurring deviation from the normal heart rhythm. With each heartbeat, an electrical impulse causes the heart to contract. In a normal heart rhythm, this contraction occurs at a regular rate. If there is something wrong with the formation or conduction of the electrical stimulus, the heart rhythm changes. For example, the heart may beat too fast or too slow. The heartbeat can also become irregular. Untreated arrhythmias can reduce the long-term pumping function of the heart or even lead to cardiac arrest. However, they are usually quite harmless and/or can be easily treated. The treatment chosen by the physician depends among other things on the patient's age and on the cause and severity of the disorder.