The catheters are threaded through veins to their permanent positions in the heart. Complications of implanting defibrillators are rare but serious and include bleeding, infections, and perforation of the heart. Implanted defibrillators monitor the heart rhythm and automatically treat, with electrical stimuli or shocks, rhythms recognized as abnormal. Newer devices also can record and store data of the electrical activity of the heart that doctors can later download and evaluate for arrhythmias. The data also can be used to perform electrophysiologic testing.
Implanted defibrillators can often stem ventricular arrhythmias with low-energy shocks.
Sometimes, however, high-energy shocks are needed. The generators in implanted defibrillators usually last three to five years and can be replaced with a surgical procedure that usually requires only local anesthesia. The electrode leads tend to last longer, although they can develop cracks or component failures that require their replacement. Medical Center found implantable defibrillators cut survivors' risk of death in half. A National Heart, Lung, and Blood Institute study under way is assessing whether implanted defibrillators or drug therapy is more effective in extending the lives of patients with ventricular arrhythmias.