Internal atrial defibrillation and implantable atrial defibrillators

Previous studies have shown that internal atrial defibrillation has been effective for the termination of individual episodes of atrial fibrillation (AF). However, no data exist as to whether repeated internal defibrillation from an implantable atrial defibrillator (IAD) would be safe and effective in maintaining sinus rhythm (NSR) in patients. The IAD philosophy, both in design and from a clinical use perspective is very different as compared to a ventricular ICD, namely, AF is not a life threatening arrhythmia. Therefore, issues such as patient tolerance of therapy versus patient perceived benefit of arrhythmia control become critical for acceptance and use of this therapy. Additionally, for both patient acceptance and safety, an IAD must favor safe and appropriate defibrillation therapy over a very high sensitivity for the arrhythmia. The only single chamber IAD available for clinical use and its 3-leads system (right atrial and coronary sinus defibrillation leads and a right ventricular bipolar lead) has been implanted in the pectoral region in over 180 patients with symptomatic, drug refractory AF. In general, these patients were without significant structural heart disease with an ejection fraction of greater than 40%. Initially, all patients received atrial defibrillation therapy under the observation of the physician. Since completion of the initial clinical trial, patients have had the ability to receive atrial defibrillation therapy in the ambulatory setting. Over 7500 shocks have been delivered from the IAD, more than 350 in the ambulatory setting, without ventricular proarrhythmia. Shock efficacy for spontaneous AF has exceeded 95%. The IAD has been shown to exhibit a high degree of specificity (100%) while maintaining a high sensitivity to AF. Conclusion: The IAD has been operating as intended in these patients. Early clinical results with the IAD have been promising in that the majority of the patients have had multiple AF episodes that have been terminated using the device and have thereby been able to remain in sinus rhythm. Conclusion: The IAD has been operating as intended in these patients. Early clinical results with the IAD have been promising in that the majority of the patients have had multiple AF episodes that have been terminated using the device and have thereby been able to remain in sinus rhythm.