Safety and efficacy of advanced atrial pacing therapies for atrial tachyarrhythmias in patients with a new implantable dual chamber cardioverter-defibrillator.

OBJECTIVES: This study evaluated the safety and efficacy of atrial pacing therapies for the treatment and prevention of atrial tachycardia (AT) or atrial fibrillation (AF) in a new dual chamber implantable cardioverter defibrillator (ICD).
BACKGROUND: Patients with an ICD may also experience AT or AF that is amenable to pace termination.
METHODS: The efficacy of atrial antitachycardia pacing (ATP) therapies for atrial tachycardia or atrial fibrillation (AT/AF) was determined in 151 patients after implantation of a GEM III AT ICD (Medtronic Inc., Minneapolis, Minnesota). The percentage of episodes successfully terminated was adjusted for multiple episodes per patient.
RESULTS: A total of 717 of 728 (96%) episodes classified as AT or AF were judged to be appropriate detections. By device classification, atrial ATP terminated 187 of 383 (40% adjusted) episodes classified as AT compared with 65 of 240 episodes classified as AF (26% adjusted, p = 0.013). Atrial Ramp or Burst+ ATP terminated 184 of 378 episodes of AT (39% adjusted), whereas 50-Hz Burst pacing therapy terminated only 12 of 109 episodes of AT (12% adjusted) and 65 of 240 episodes of AF (26% adjusted). If efficacy was defined as termination of AT/AF within 20 s of delivery of the pacing therapy, ATP therapies terminated 139 of 383 (32% adjusted) episodes of AT compared with 34 of 240 episodes of AF (15% adjusted, p = 0.003). Efficacy was dependent on AT cycle length. Frequent transitions between AT and AF predicted inefficacy of atrial ATP (p < 0.001). Ventricular proarrhythmia secondary to atrial ATP was not observed.
CONCLUSIONS: Atrial ATP therapies terminate many episodes of AT without ventricular proarrhythmia. The addition of 50-Hz Burst pacing has minimal efficacy for AT/AF.