Defibrillation, or shock, can be the only way to stop certain heart arrhythmias, or irregular heartbeats, before they kill. If the heart beats too quickly, the chambers, or ventricles, will not have enough time to fill with blood and pump blood to the rest of the body, which can cause death. For people at high risk for the deadliest forms of arrhythmias – called ventricular tachycardia and ventricular fibrillation – an internal “shocking” device may be the best protection against sudden cardiac arrest (SCA).
Implantable cardioverter defibrillators (ICDs) are used to detect dangerously fast heartbeats and give a lifesaving shock to correct the heart’s rhythm. A person with an ICD has the equivalent of a paramedic sitting on his shoulder, always watching and ready to give the heart “the paddles,” as seen on many hospital and emergency television shows.
ICDs are devices that are about the size of a business card and implanted below the collarbone in a pocket
under the skin. Like pacemakers, ICDs contain a generator containing a computer, battery, and wires called “leads” that usually go through a vein into the heart. The leads stay in contact with the heart muscle on one end, while the other end is connected to the generator. The battery in the generator lasts 5-8 years and must be replaced when it runs out.
The ICD is pre-programmed to send signals to the heart. ICDs can be “talked to” with a device that gives doctors information about the person’s heart rhythms and the overall condition of the ICD. This follow up is very important to make sure the ICD is working for each patient.
Today, all ICDs also act as pacemakers and can prevent slow heart rhythms as well. Pacing signals from the ICD are not felt by the patient, but the shock signal delivered by an ICD has been described as a “kick in the chest.” Medication or other treatments may be given to try to reduce any pain from ICD shocks.
People with heart muscle damage or heart failure have a greater chance of having dangerously fast heart rhythms. ICDs are often recommended for people who have this problem even if they have not yet had an abnormal heart rhythm.
ICDs do not prevent heart attacks, which are caused by blockages in the heart’s arteries, but do treat abnormal rhythms sometimes associated with heart attacks. ICDs do not keep people alive forever. People with ICDs can die of causes other than heart rhythm problems.