Implantable Cardioverter Defibrillator

What Is an ICD

An ICD, short for implantable cardioverter defibrillator, is a battery-powered device implanted under the skin of the chest to prevent sudden cardiac death. Sudden death is usually caused by a very fast or chaotic rhythm in the ventricles, namely ventricular tachycardia or ventricular fibrillation, so the heart can no longer pump blood. An ICD recognizes these rhythms within seconds and tries to stop them. This condition is covered on the Sudden Cardiac Death page.

How It Works in Brief

The generator contains a battery and electronic circuitry, while the lead (wire), whose tip sits in the right ventricle, records every heartbeat. If a fast ventricular rhythm is detected, the ICD can first try rapid pacing, which is usually painless. If this does not work or the rhythm is very chaotic, the ICD delivers an electrical shock to restore a normal rhythm. An ICD also paces the heart when the heartbeat is too slow and stores rhythm recordings for the doctor to review.

Who Needs an ICD

There are two groups. First, people who have survived cardiac arrest or had severe ventricular tachycardia without a reversible cause; this is called secondary prevention. Second, people who have never had these events but are at high risk, especially if the heart's pumping strength, called the ejection fraction, remains 35 percent or less after about 3 months of guideline-based heart failure treatment; this is called primary prevention. Some inherited heart diseases, such as high-risk hypertrophic cardiomyopathy, long QT syndrome, or Brugada syndrome, can also be a reason.

Types of ICDs

A transvenous ICD uses a lead inserted through a vein into the right ventricle. A subcutaneous (under-the-skin) ICD uses a lead placed under the skin beside the breastbone, with no lead inside the heart, but it cannot pace the heart over the long term. In heart failure with certain conduction disorders, an ICD can be combined with a resynchronization device into a CRT-D, which is covered on the Cardiac Resynchronization Therapy (CRT) page.

What You Should Know

An ICD does not prevent arrhythmias from occurring and does not cure the underlying heart disease. Heart failure medicines and rhythm medicines are still needed, as covered on the Heart Failure Management page. The decision to implant an ICD should be made together, including discussing shocks, driving rules, and your overall health.

Patients usually stay one night. Before you go home, the device is checked, a chest X-ray is taken, and you receive a device identification card.

Wound and arm. Keep the wound dry for about 1 week. Avoid raising the arm on the device side above your shoulder and avoid heavy lifting for about 4 to 6 weeks.

If you receive a shock. A shock feels like a strong jolt in the chest for an instant. If it happens only once and you feel well, contact the team to schedule a device check.

Driving. The waiting period differs depending on the reason for implantation, usually about 1 week for primary prevention and about 3 months after cardiac arrest or after receiving a shock. Rules for public transport drivers are stricter.

Device checks. Regular checks at the clinic and from home, which are covered on the Remote Heart Monitoring page. The battery usually lasts about 6 to 10 years.

Emotional support. Feeling anxious after implantation or after a shock is normal. Talk with the team; support from family and counseling can help.

Warning signs to watch for. Go to the emergency room right away if you experience:

• Two or more shocks within 24 hours
• A shock with chest pain, shortness of breath, or fainting
• A wound that is red, swollen, or oozing pus, or accompanied by fever
• Swelling at the device pocket that keeps getting bigger
• Sudden shortness of breath or chest pain