Stanford Cardiac Arrhythmia Service

Implantable Cardioverter-Defibrillator (ICD)

Some patients are felt to be at increased risk of having life-threatening arrhythmias.  These patients may have had an episode of ventricular tachycardia or a cardiac arrest and were resuscitated.  Other patients have evidence of impaired pumping function of the heart and are felt to be at risk for life-threatening ventricular arrhythmias. 

What does an ICD do?

The main role of an ICD is to detect and rapidly convert a life-threatening ventricular arrhythmia.  The ICD works by providing a shock to the heart or by pacing the heart rapidly. 

There are a number of categories of patients with indications for ICD implantation.

  1. Patients with prior cardiac arrest
  2. Sustained ventricular tachycardia in the setting of structural abnormalities of the heart
  3. Decreased Ejection Fraction  (35% or less) and impaired exercise capacity
  4. Decreased Ejection Fraction (30% or less) and coronary artery disease
  5. Hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, and long QT with risk factors for sudden cardiac death


The procedure is performed in the electrophysiology laboratory. The patient may be given either sedation or general anesthesia.  The physician will inject a local anesthetic in  the upper chest area to numb the skin and tissue which is where the device will be placed.  Access to the vein under the collar bone is obtained and one or more leads (thin wire-like tubes) are advanced to the heart. The leads are connected to the ICD and closed up under the skin.  In most cases, testing of the ICD will be performed consisting of producing a serious ventricular arrhythmia called ventricular fibrillation and observing the ICD detect and convert it with a shock. 


There is about a 1-2% risk of stroke, heart attack, death, damage to the heart or lungs requiring surgery, including puncturing the heart but this risk may vary based on the patient’s condition.  There is a risk of bleeding and bruising, damage to the artery, nerves, and veins requiring surgery or transfusions, blood clots and swelling and infection.   There is about a 5% chance of the lead dislodging requiring reoperation.  There is about a 1% risk of failure of the device before the usual 4-7 year replacement duration.  For about 4 weeks it is important to avoid lifting the arm on the side of the ICD above the level of the shoulder to decrease the risk of dislodging the leads.  There is a risk of damage to the lead so repetitive motion on the side of the ICD should be avoided long-term.

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