A pacemaker is a device implanted in the chest through surgery and helps control irregular heartbeat (Arrhythmia), usually preventing the heart from beating too slowly. Depending on the condition a patient can have either a single-chamber pacemaker, dual-chamber pacemaker, or biventricular pacemaker.
Implantable Cardioverter Defibrillator (ICD) also serves as a pacemaker and is helpful in preventing sudden death. ICD continuously tracks the heartbeat pattern, if an abnormal pattern is detected it gives an electric shock to restore the normal heartbeat.
Cardiac Resynchronization Therapy (CRT) is for patients who are more prone to heart failure and arrhythmia.