Medical Health Encyclopedia

Implantable cardioverter-defibrillator

Injury Disease Nutrition Poison Symptoms Surgery Test Special Topic

A B C D E F G H I J K L M N O P R S T U V W Y

Heart, section through the middle Heart, front view Normal heart rhythm Conduction system of the heart

Overview

Implantable cardioverter-defibrillator

Alternative Names:

ICD

Information:

Text Continues Below

---

An implantable cardioverter-defibrillator (ICD) is a device designed to quickly detect a life-threatening, rapid heartbeat coming from the bottom chamber of the heart. It converts the abnormal rhythm back to normal by delivering an electrical shock to the heart. An ICD can effectively prevent sudden cardiac death.

An ICD is a minicomputer that consists of:

• a pulse generator with batteries and a capacitor that can send a powerful shock to the heart
• an electronic logic circuit to tell the ICD when to discharge.
• lead electrodes placed in the heart (or, rarely, small electrodes placed under the skin), to sense the cardiac rhythm and deliver the shock to the heart muscle.

All ICDs have a built-in pacemaker. Pacing may be necessary to support the heart in some instances, for example, after a shock, or during a very slow heart beat. The pacemaker also allows the device to correct heartbeats that are too fast.

The ICD continously monitors the heartbeats for regularity. It only delivers a shock to the heart when it senses a life-threatening rhythm.

During the implantation of a pacemaker-type ICD, electrodes are inserted through the veins into the heart. The pulse generator is surgically buried under the skin of the chest, generally below the left collarbone.

Who needs an ICD?

In some people, the lower chamber of the heart either suddenly starts beating in a disorganized manner (ventricular fibrillation or VF), or it starts beating very rapidly (ventricular tachycardia or VT). Both VF and VT can make the heart stop pumping blood, leading the person to a sudden loss of consciousness or death. Abnormal rhythms, like VT and VF, require emergency treatment and are best treated in hospital coronary care units. In these units, VT and VF can be converted back to the normal rhythm by an electric shock given across the chest (external defibrillation).