An implantable cardiac rhythm device is used to regulate an irregular heartbeat by sending electrical signals to the heart to alter its rhythm.
These devices are surgically implanted under the skin, typically just below the collarbone. A small, battery-operated computer generates the electrical signal (pulse generator), which is transmitted to the heart via one or more electric wires (leads).
There are three main categories of implantable cardiac rhythm device.
These deliver specifically timed, low-energy electrical impulses to the heart. Pacemakers help maintain adequate heart rate when the heart rate is not fast enough (bradycardia) or there is a block in the heart's electrical conduction system (heart block).
Also called biventricular pacemakers, these have at least two leads implanted in the heart to simultaneously stimulate both the left and right lower chambers (ventricles) to make them contract at the same time. A third lead may be implanted to coordinate the upper (atria) and lower chamber contractions.
These act as a permanent safeguard that corrects sudden, life-threatening arrhythmias with high-energy pulses (cardioversion or defibrillation). ICDs are used in people who are at high risk for having a potentially life-threatening heart rhythm (ventricular tachycardia or ventricular fibrillation) or who have survived such an event. Some CRT pacemakers have additional ICD capacity to provide additional protection if required.