INDICATIONS FOR DUAL-CHAMBER (DDD) PACING IN IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR PATIENTS

New technologic development of implantable cardioverter-defibrillators (ICDs) keeps up with the exponential increase of their use for primar y and secondary prevention of sudden cardiac death. The first-generati on ICD with limited shock capability alone could be considered adequat e in most cardiac arrest victims, but it wets not suitable for sudden death prevention in all high-risk patients with cardiac disease. The s econd-generation ICD was comprised of hybrid pacemaker-defibrillator s ystems that provided on-demand ventricular antibradycardia pacing. The third-generation devices include additional functions, such as antita chycardia pacing for ventricular tachycardia (VT) reversion and low-en ergy ventricular cardioversion, in addition to ventricular defibrillat ion and single-chamber ventricular demand pacing. In the near future, advanced dual-chamber atrioventricular (AV) pacing and defibrillating systems will also be available. The dual chamber ICD will allow atrial inhibited/dual-chamber (AAI/DDD) rate-responsive pacing, simultaneous atrial and ventricular sensing to optimize the arrhythmia identificat ion, and ICD shock delivery In the proper arrhythmia-related chamber. Clinical benefits of these devices compared with their cost and comple xity will require careful evaluation.