SPECIFIC CONSIDERATIONS WITH THE AUTOMATIC IMPLANTABLE ATRIAL DEFIBRILLATOR

Automatic Implantable Atrial Defibrillator, Introduction: Internal atr ial defibrillation has been evaluated as an alternative approach to th e external technique for more than two decades. Previous studies in an imals and humans have shown that internal atrial defibrillation is fea sible with relatively low energies. The promising results achieved wit h internal atrial defibrillation have facilitated the development of a n implantable atrial defibrillator (IAD). Methods and Results: For any new therapy, it is imperative to demonstrate safety, efficacy, tolera bility with improvement in quality of life, and cost-effectiveness com pared with therapeutic options already available. Maintenance of sinus rhythm or prolonged duration in arrhythmia-free intervals should be d emonstrated clearly with an IAD. Initial clinical experience with the Metrix(TM) system indicates stable atrial defibrillation thresholds, a ppropriate R wave synchronization markers,no shock-induced ventricular proarrhythmia, and excellent detection of atrial fibrillation (AF) wi th a specificity of 100%. Ventricular proarrhythmia has not been repor ted for correctly R wave synchronized low-energy shocks when closely c oupled to RR intervals, and long-short cycles are avoided. Conclusion: Preliminary experience with the Metrix system suggests that the PAD m ay offer a therapeutic alternative for a subgroup of patients with dru g-refractory, symptomatic, long-lasting, and infrequent episodes of AF . Further efforts must be undertaken to reduce the patient discomfort associated with internal atrial defibrillation in an attempt to make t his new therapy acceptable to a larger patient population with AF.