Implantable Cardioverter Defibrillator (ICD)

Your Care Explained > Devices : Implantable Cardioverter Defibrillator (ICD)

An ICD is an electronic device that constantly monitors your heart rate and rhythm and automatically corrects abnormal rhythms.

Even though ICDs are equally effective in men and women with heart failure, they have traditionally been less likely to be implanted in women. At Brigham and Women’s Hospital, we believe it’s a valuable, life-saving solution for all patients at high risk for heart attack or sudden cardiac death.

How an ICD Works

An ICD is similar to a pacemaker; it consists of a battery-powered pulse generator and leads. The pulse generator, which is about the size of a man’s wallet, is implanted in a pouch under the skin of the chest or abdomen. Wires or leads run from the pulse generator to positions on the surface of or inside the heart and deliver electrical signals between the pulse generator and the heart. A computer in the pulse generator continuously monitors heart rhythms. If it detects dangerous arrhythmias such as ventricular tachycardia or ventricular fibrillation, it sends a signal down the lead that stimulates the heart back to normal rhythm. The pulse generator records all its activity so your doctor can access the information and, if necessary, adjust its settings.

Living with an ICD

Your ICD may be programmed to correct a heart rate that is too slow or fast, as well as abnormal heart rhythms. When it detects an abnormal rate or rhythm it sends an impulse, or shock, that you probably won’t feel. If the first shock does not reset your heart rhythm, the device will send progressively stronger shocks until the heart converts to a normal rate. These stronger shocks may feel like thumps or even kicks in the chest. However, they last for only a few seconds.

Strong electric or magnetic fields can interfere with the ICD. Although most security devices don’t interfere with ICD function, the metal case may set them off. Instead of walking through, you may want to show your ICD identification card and ask the guard to use the hand scanner. The anti-theft gates in department stores may emit electronic signals. It’s a good idea to pass through them quickly and not to linger near them. Microwave ovens don’t pose any danger. Cell phones are also pretty safe, unless they are held over the heart. It may be a good idea to use an ear plug and keep the phone away from your chest while you’re talking. Certain types of hospital equipment, such as a magnetic resonance imager (MRI), can interfere with your ICD function. Remember to let the radiology staff know that you have an ICD if you’re scheduled for an imaging procedure.

Date Last Modified: January 21, 2011

Send Feedback To: BWH Women’s Health at

75 Francis Street, Boston, MA 02115 617.732.5500
harvard medical school partners healthcare © BWH 2011