Defibrillator Implantation
What is an implantable cardioverter defibrillator?
The implantable cardioverter defibrillator (ICD) is an electronic device like a large pacemaker that is implanted surgically in a pocket formed in the chest wall. It consists of a pulse generator that can deliver a powerful shock to the heart and wires to sense the heart's rhythm. Since all ICDs contain pacemakers as part of their circuitry, they are properly called defibrillator-pacemakers. The first implantable defibrillators required open-chest surgery to implant the wires. Fortunately, the present units do not require open chest surgery for implantation. The wires can be inserted through a large vein that runs beneath the collarbone and directed into the heart under x-ray guidance. The pulse generator is then buried under the skin of the chest wall. The procedure for implanting an ICD is similar to a pacemaker implant.
Why are ICDs needed and how do they work?
Some people are at very high risk for sudden death. This group includes those whose heart suddenly stops pumping blood due to loss of an organized heartbeat (ventricular fibrillation) or an excessively rapid heartbeat (ventricular tachycardia). These rhythm disturbances can result in loss of consciousness and/or death. When these rhythms occur in a hospital setting such as the coronary care unit, an electrical shock can be quickly given, restoring the heart to a normal rhythm. Most episodes, however, occur outside hospitals and the victims can die unless CPR is administered quickly and defibrillation accomplished by a medic unit. Because the resources are not always available in a timely fashion, patients at high risk for these events may receive an ICD. When a life threatening rhythm is detected, the device can deliver a powerful electrical shock to the heart restoring normal rhythm. A variety of sophisticated electrical therapies can be selected by your cardiologist depending on the type of heart rhythm being treated. The batteries are designed to last approximately 5 to 7 years and deliver about 100 shocks.
Who is a candidate for an ICD?
Today's candidates for an ICD fall into three categories. The first is someone who has recurrent ventricular tachycardia that is poorly controlled by drugs.
The second group is those patients who have survived cardiac arrest. Such people are at high risk for another episode of ventricular fibrillation. The third group is patients who have never had an abnormal heart rhythm but are thought to be at high risk. Prior to implantation of an ICD, a sophisticated test called an electrophysiological study (EPS) may be performed. This procedure measures the vulnerability of the heart for a potentially fatal event. It is used to help decide whether to use an ICD or whether to use drugs for treatment.
What are the benefits of an ICD?
Currently, available research shows that ICDs prolong life in people who have them. For many, the quality of life is much improved. Many do not need to take antiarrhythmic drugs, which often have uncomfortable side effects. Many patients greatly appreciate the peace of mind given them by the device. They no longer have to worry about spells of unconsciousness. Some can resume driving automobiles without worry.
What are the complications of an ICD?
The defibrillator unit can cause local discomfort. The most common long-term complication is the delivery of shocks when the patient does not need them. This is less of a problem with more recent devices. The patient is usually quite aware of each shock, even though it is very short in duration. The patient's doctor should be notified of every shock. When the batteries have depleted their energy, the pulse generator must be replaced. Replacement of the pulse generator requires only minor surgery.
What happens after ICD implantation?
Recovery time after implantation of newer ICD units is quite short. Hospital stays are rarely longer than 1 or 2 days and there is quick return to prior activity levels. People with ICDs must continue to follow their doctor's recommendations regarding medication, diet, and exercise.