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.

Permanent pacemakers 

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).

Cardiac resynchronization therapy (CRT) pacemakers 

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.

Implantable cardioverter-defibrillators (ICD) 

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.

Catheter ablation is an invasive procedure that targets faulty electrical tissue in the heart. It is used primarily to treat people with atrial fibrillation or rapid heartbeat. In most cases, the diagnostic test (electrophysiology study) and the treatment (cardiac ablation) are performed as part of the same procedure.

During the diagnostic electrophysiology study, special catheters (thin flexible tubes) are inserted through a vein in your arm, groin or neck and guided to your heart. The procedure involves triggering certain heart rhythms and mapping the electrical activity of the heart cells. This helps pinpoint the abnormal tissue causing the arrhythmia. Based on this information, doctors will decide whether catheter ablation would be useful to treat the arrhythmia. If so, the treatment will proceed immediately.

During catheter ablation treatment, a special catheter is placed in the dysfunctional area identified by the electrophysiology study. The catheter then uses heat or cold to damage the tissue. The resulting scar (ablation) creates a barrier that isolates the faulty electrical section from healthy heart tissue. This prevents abnormal electrical signals from traveling to the rest of the heart and causing arrhythmias.