UNIPOLAR PECTORAL DEFIBRILLATION SYSTEMS

Over the past 15 years, the implantation of automatic defibrillators h as evolved from an obscure, impractical, and often morbid procedure to nearly a routine therapy. Initial large abdominally implanted generat ors with multiple epicardial leads have given way to much smaller, pec torally implanted systems utilizing only a single lead. These systems are better accepted by physicians and patients and are rival recent-ge neration pacemakers in their implantation simplicity. Outcomes with si ngle lead defibrillator implantation have been excellent. They are 99% effective at eliminating sudden death in large cohorts of patients, w ith overall survival of 94.4% at 18 months. Previously significant per ioperative complications and mortality associated with epicardial syst ems have been virtually eliminated. Transvenous single lead systems no w provide defibrillation efficacy at a level that makes epicardial lea ds unnecessary in most patients. Although inappropriate shocks are not a morbid complication, they still occur in approximately 15%-30% of p atients. This is an area for improvement in defibrillator therapy, whi ch, though invisible in total mortality statistics, is significant in terms of patient comfort and acceptance. Incremental improvements in p ulse generator design and defibrillator lead technology are being made . Perhaps the most interesting new development will be the dual chambe r device, incorporating an atrial electrode for sensing, pacing, and p erhaps, atrial defibrillation. Such improvements will continue to make device therapy of all arrhythmias more versatile and improve patient comfort both in terms of device size and inappropriate shocks. It is u nlikely, however, that further technological advances can further dimi nish the already small complication rate or improve the already excell ent efficacy of current pectoral single lead systems. Defibrillator te chnology has already reached a maturity where technological improvemen ts are less significant than efforts to better define the patient popu lation who will benefit from the therapy.