Worldwide, nearly 4 million patients currently have cardiac implantable electronic devices. Due to the increasing number of candidates to receive either pacemakers or implantable cardiac defibrillators, there is no doubt that primary care physicians or anesthesiologists are very likely to interact and deal with this particular patient population. However, besides technologic advancements, several factors have been frequently reported to cause confusion regarding their perioperative care. Therefore, it has become extremely valuable to understand the basic functions and operation of these devices, as well as their functional limitations, to prevent iatrogenic complications and detect potential failure in an early stage.