Clinical Electrophysiology: Pacemakers Defibrillators

Pacing and rhythm-control devices, including pacemakers and implantable cardioverter defibrillators (ICDs), are used to treat arrhythmias or other disturbances of the heart's rhythm. These devices send and receive electrical signals to and from the heart, regulating heartbeat and are life saving in many situations.  

Permanent Pacemakers

These devices are used to treat slow heart rhythms (bradycardia). Permanent pacemakers are placed inside the chest through a major vein and are intended to remain in the body over a long period. The pacemaker is implanted during a procedure when the patient is under local anesthesia. A vein in the upper chest is opened so the pacemaker wires can be advanced into the heart. The wire must touch the heart to carry electrical signals back and forth between the heart and the pacemaker. The wire is then attached to the pacemaker, which is put under the skin in a pocket-like pouch under the skin.

Implantable Defibrillator

An implantable cardioverter defibrillator (ICD) is an electronic device designed to stop rapid, life threatening heart rhythms. If the heart has stopped (cardiac arrest) or is experiencing rapid, abnormal heart rhythms (life-threatening arrhythmias) that cannot be controlled by drugs or other approaches, this device may be used. It may also be used in patients with very weak heart muscle where there is an increased risk of developing dangerous heart rhythms.

The defibrillator uses two approaches to stop rapid, abnormal heart rhythms. The device can stimulate the heart to beat faster than the abnormal rate, which is called overdrive pacing, or it can deliver one or more electrical impulses directly to the heart to stop the rhythm.

The defibrillator is placed in a pocket under the skin of the chest. The device consists of leads and a pulse generator. The leads monitor the heart rhythm and deliver the energy for pacing, cardioversion and/or defibrillation. The generator contains the battery and a tiny computer that processes information to determine the heart's rhythm.

There are three types of ICDs: single, dual chamber and biventricular devices. In a single-chamber ICD, a lead is attached to the right ventricle. In a dual-chamber ICD, leads are attached to the right atrium and the right ventricle. There is also a biventricular ICD, in which leads are attached in the right atrium, the right ventricle and the left ventricle. The biventricular ICD is for patients who have had heart failure to provide cardiac resynchronization therapy.

Cardiac Resynchronization Technology

Cardiac resynchronization technology (CRT) is an innovative approach for patients with congestive heart failure. Building on the technology for pacemakers and implantable cardioverter devices, CRT uses a specialized pacemaker to re-coordinate the action of the right and left ventricles. This differs from typical pacemakers, which pace only the right ventricle. CRT seeks to coordinate the heart's contractions and improve pumping ability and overall heart function.

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