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In this Article

• What are implantable cardiac defibrillators (ICDs)?
• How does a normal heart function?
• How do abnormal heart rhythms decrease blood delivery by the heart?
• What is the cause of tachycardias?
• What are the symptoms of tachycardias?
• What are life-threatening tachycardias?
• What are the causes of ventricular tachycardia and ventricular fibrillation?
• How can ventricular tachycardia and fibrillation be treated and prevented?
• Who should receive an ICD?
• How are ICDs designed?
• How are ICDs implanted?
• What happens after implantation of an ICD?
• What are the complications of ICD implantation?
• What happens during a tachycardia episode after the placement of an ICD?
• Living with an ICD.
• What outside electrical sources are safe?
• What outside electrical sources can interfere with the ICD?
• What does the future hold for ICDs?
• Implantable Cardiac Defibrillators At A Glance
• Implantable Cardiac Defibrillator Index
• Find a local Cardiologist in your town

What are the complications of ICD implantation?

Common complications include pain, swelling, and minor bleeding at the implantation site. More serious complications are uncommon and typically occur less than 2% of the time. Serious complications include major bleeding requiring blood transfusions, introduction of air into the space between the lung and chest wall (pneumothorax) requiring tube drainage, perforation of the heart muscle by the leads, activation of an intractably fast heart rhythm, stroke, heart attack, need for emergency heart surgery, and death. Although there are no official guidelines, ICDs should be implanted by or in conjunction with a cardiologist specially trained in clinical cardiac electrophysiology (electrical diseases of the heart).

What happens during a tachycardia episode after implantation of an ICD?

When the heart is beating normally, the ICD remains inactive. When tachycardia occurs, the patient typically experiences the symptoms of a fast heart rate. Since tachycardia can lower blood pressure and cause dizziness or fainting spells, the person should lie down or sit down until the symptoms pass. The ICD will either send a series of pacemaker-like weak electrical signals or one or more low energy shocks to convert the tachycardia to normal rhythm. The patient may not feel the pacemaker-like signals, while the low energy shocks may feel like thumps in the chest. Terminating a tachycardia with low energy shocks is called cardioversion.

If ventricular fibrillation occurs, the patient may suddenly feel faint or lose consciousness due to lack of blood pressure and blood supply to the brain. The ICD, sensing the rapid and irregular rhythm, quickly sends a strong shock to terminate the rhythm. Terminating fibrillation with a strong electric shock is called defibrillation. Successful defibrillation promptly restores consciousness. If unconsciousness lasts longer than 30 seconds, emergency 911 should be called.

The patient, or anyone available to assist, should also call emergency (911) if any of the following occur:

1. Symptoms of tachycardia persist after feeling the shock(s);
2. Symptoms of tachycardia persist and the patient feels no shocks (possible ICD malfunction); or
3. The patient feels a series of shocks in a row (possible ICD malfunction or recurrent attacks of tachycardias). Both conditions need prompt medical attention.