context: Treatment for abnormal heart rhythms is possible with an ICD, or implantable cardioverter defibrillator. An ICD is an electronic device that constantly monitors your heart rate and rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle. This causes the heart to beat in a normal rhythm again. The ICD has two parts: the lead(s) and a pulse generator. The lead(s) are made up of wires and sensors that monitor the heart rhythm and deliver energy used for pacing and/or defibrillation (see below for definitions). The generator houses the battery and a tiny computer. Energy is stored in the battery until it is needed. The computer receives information from the leads to determine how the heart is beating. There are different types of ICDs, including: Single-chamber ICD. A lead is attached in the right ventricle. If needed, energy is delivered to the ventricle to restore a normal heart rhythm. Dual-chamber ICD. Leads are attached in the right atrium and the right ventricle. Energy can be delivered to the right atrium and then to the right ventricle, helping your heart to be paced in a normal sequence. Biventricular ICD. Leads are attached in the right atrium, the right ventricle and the coronary sinus, adjacent to the left ventricle. This technique helps the heart beat in a more efficient way and is specifically used for patients with heart failure. Your doctor will determine which type of ICD is best for you. The ICD monitors the heart rhythm, identifies abnormal heart rhythms, and determines the appropriate therapy to return your heartbeat to a normal rhythm. Your doctor programs the ICD to include one or all of the following functions: Antitachycardia Pacing ( ATP). When the heart beats too fast, a series of small electrical impulses are delivered to the heart muscle to restore a normal heart rate and rhythm. Cardioversion. A low-energy shock is delivered to restore a normal heart rhythm. Defibrillation. When the heart is beating dangerously fast, a high-energy shock is delivered to the heart muscle to restore a normal rhythm. Bradycardia pacing. When the heart beats too slow, small electrical impulses stimulate the heart muscle to maintain a suitable heart rate. ICDs are used for: People who have had an episode of sudden cardiac arrest or ventricular fibrillation. People who have had a heart attack and are at high risk for sudden cardiac arrest. People who have hypertrophic cardiomyopathy and are at high risk for sudden cardiac arrest. People who have dilated cardiomyopathy with severely reduced heart function and are at high risk for sudden cardiac arrest. People who have had at least one episode of ventricular tachycardia, an abnormal heart rhythm. Before you have your ICD implanted, ask your doctor what medications you are allowed to take. Your doctor may ask you to stop taking certain medications before the procedure. You will receive specific instructions. If you have diabetes, ask your doctor how you should adjust your diabetes medications. Do not eat or drink anything after midnight the evening before the procedure. If you must take medications, drink only with a sip of water. When you come to the hospital, wear comfortable clothes. You will change into a hospital gown for the procedure. Leave all jewelry and valuables at home. When you have an ICD implanted, you will start by lying on a bed and the nurse will place an intravenous line ( IV) into your arm or hand. This is so you may receive medications and fluids during the procedure. You will be given an antibiotic to prevent infection and a medication through your IV to relax you and make you drowsy, but it may not put you to sleep. The nurse will connect you to several monitors. The monitors allow the doctor and nurse to check your heart rhythm, blood pressure, oxygen level of your blood, and other measurements during the procedure. The left or right side of your chest, from your neck to your groin will be shaved and cleansed with a special soap. Sterile drapes are used to cover you from your neck to your feet. A soft strap will be placed across your waist and arms to prevent your hands from coming in to contact with the sterile field. The ICD may be implanted in two ways, but the endocardial (transvenous) approach is most common. A small incision is made under the collarbone. The lead is placed into a vein and guided inside your heart chamber. The generator is placed under skin in your upper chest and attached to the lead(s). On rare occasion, it may be necessary for your doctor to implant your ICD using the epicardial approach (outside your heart). This requires open-heart surgery. Instead of placing the lead through a vein and guiding it to the heart, it is sewn onto the heart. Minimally invasive approaches, such as robotic-assisted surgery, are available to lessen the trauma associated with this type of surgery. Your doctor will decide if this approach is necessary for you. The ICD implantation procedure takes about two to five hours to perform. You will normally be admitted to the hospital overnight after your ICD is implanted. The morning after your implant, you will have a chest X-ray to make sure the ICD leads are in the proper position and your ICD will be programmed to ensure it is functioning properly. You will receive information about the type of ICD and leads you have, the date of implantation, and the name of the doctor who performed the procedure. In about three months after the procedure, you will receive a permanent identification card with this information. It is important that you carry this card with you at all times in case you need medical attention. For the first six weeks after the procedure, avoid lifting, pushing, or pulling objects that weigh more than 10 pounds. If you had open-heart surgery, it may take longer for you to get back to some activities. Your doctor or nurse will discuss specific activity guidelines with you before you leave the hospital. Keep the wound clean and dry. Look at your wound every day to make sure it is healing. It will take a few weeks to heal completely. Call your doctor if you notice: Unusual redness Swelling Drainage from the wound Fever Chills You will have a slight bulge under the skin where the generator is located. It will not be noticeable under clothes. Avoid wearing tight fitting clothing so your incision will not be irritated. Most electrical devices, such as microwave ovens, do not interfere with ICD function. You need to avoid strong electric or magnetic fields, such as some industrial equipment, MRI machines, high-output ham radios, high-intensity radio waves (found near large electrical generators, power plants, or radio frequency transmission towers), and arc or resistance welders. Stay at arm's length from less powerful electric or magnetic fields, such as large magnets, stereo speakers, airport security wands, and antennas used in ham or CB radios. If you are in stronger electrical or magnetic fields, the ICD may stop monitoring your heart rhythm. Once you are out of these fields, normal ICD function should resume. No permanent damage should be done to the ICD. Cellular phones should be kept at least 6 inches from your ICD. Do not store cell phones in a pocket over the device. If you must pass through entrances where theft devices are being used, walk quickly through them. Your doctor may tell you not to undergo tests that require magnetic resonance imaging ( MRI). You may have CT scans done if necessary. If you have concerns about your job or activities, ask your doctor. You may or may not be aware of when your ICD detects and corrects your heart rhythm. Often it depends on the type of therapy you receive. Pacing. You may or may not feel the impulses -- usually they are not detectable. Defibrillation. The shock feels like a kick in the chest but only lasts for a moment. Some patients describe the sensation as feeling like a shock from an electrical outlet. Most times, you will be awake when the shock is delivered, but on occasion, you may lose consciousness before the therapy is delivered. If you get shocked by your ICD: Stay calm. Sit or lie down. Ask someone to stay with you. If you do not feel well after the shock, call your doctor or an ambulance (dial 911 in most areas). If you feel fine after the shock, you do not need to seek immediate medical attention. Call your doctor within 24 hours. If someone is touching you when the ICD fires, they may feel a tingling sensation; this is not harmful to them. Call your doctor about your ICD if: You receive 2 or more shocks in a 48-hour period. You lose consciousness before receiving a shock. You have swelling, bleeding, redness, warmth, or drainage at the implant site. You have numbness or tingling of the arm closest to your ICD. Any part of the device or leads is visible or protruding through the skin. You have a fever or chills within 6 weeks to 8 weeks after the implant procedure. Regular follow-up is important after an ICD implant. Your doctor will tell you how often you will need to have the ICD checked. During ICD checks, the doctor will determine if the ICD has detected or treated any abnormal heart rhythms and will check the ICD battery. These visits are very important. You will also need to see a cardiologist at least once a year. A defibrillator lasts five to ten years, depending on how often it delivers a shock. When you need your ICD changed, you will be admitted to the hospital for the procedure. An incision is made above the ICD and the ICD is removed. The leads are tested. If the function of the leads is acceptable, they will be attached to a new generator. Otherwise, new leads may be inserted.