Cardiac arrhythmias are disorders associated with abnormal electrical activity of the heart. Such disorders manifest in the heart beating too fast or too slow, or might manifest in an irregular heartbeat. Arrhythmias may occur occasionally in healthy hearts but are of minor consequence. However, in other cases, arrhythmias may indicate a serious problem and lead to heart disease, stroke or sudden cardiac arrest.
Artificial Pacemaker & Implantable Cardioverter-Defibrillator
Cardiac arrhythmias can be treated with implantable medical devices that use electrical impulses to regulate the beating of the heart. Generally, two basic types of devices are distinguished: the artificial pacemaker and the implantable cardioverter-defibrillator (some devices combine defibrillation and pacing function in a single device).
Devices that correct the heart rate are traditionally called artificial pacemakers. They correct irregularities of the sinus node, the natural pacemaker tissue of the heart. Irregular activity of the sinus node might result in signals that are either too slow (sinus bradycardia) or in signals that are temporarily suspended (sinus arrest). Other irregularities might manifest in improper electrical signal transmission from the atria (the top heart chambers) to the ventricles (the bottom heart chambers). In all cases, artificial pacemakers are used to maintain an adequate heart rate.
The first implantable pacemaker (CC Professor Marko Turina, University Hospital, Zurich).
Devices that correct irregular heart rhythms (as opposed to heart rates) are called implantable cardioverter-defibrillator (ICD). They are, like pacemakers, small electrical impulse generators implanted in patients. As the name suggest, defibrillators counter the effects of fibrillation, a life-threatening event in which the heart muscle cells contract chaotically.
Pacemakers and defibrillators contain a battery, electrodes that measure the naturally occurring activity of the heart, an amplifier for these signals and an integrated circuit that computes and delivers impulse to the heart. The devices are hermetically sealed and usually made of titanium to avoid rejection by the immune system. Most commonly, the devices are placed below the fat layer of the chest wall. However, the placement may vary on a case-by-case basis. The most modern devices contain a wireless emitter that is able to send critical information to the physician. If any abnormal problems are detected, an intricate system will alert the physician at any time of the day or night.