Antitachycardia pacing therapies to terminate atrial tachyarrhythmias: the AT500 Italian Registry

Background Antitachycardia pacing (ATP) therapies may have a role to play in treating paroxysmal atrial tachy-arrythmias. The Medtronic AT500 is a new DDDRP pacemaker providing automatic ATP therapies and prevention algorithms. Method A total of 131 patients (age 71 +/- 9 years, 71 mate and 60 female) were enrolled in the AT500 Italian Registry after receiving the device. After implant, diagnostic features were enabled. They classify arrhythmias as atrial fibrillation (AF) or atrial tachycardia (AT) according to their rate, atrioventricular association and regularity. ATP therapies and prevention algorithms were enabled at first month follow-up visit. ATP therapies were programmed to treat episodes classified as AT at their onset or during their progression. Therapies were automatically delivered 1 min after episode detection. Results During a follow up of 3.3 +/- 2.9 months, 5593 AT/AF episodes were detected and treated in 21 patients, and 2065 (36%) were classified by the device as successfully terminated. In a subgroup of patients for whom electrogram information was available, the device classified 96 (37.4%) of the 256 recorded episodes as successfully terminated. The effect of ATP on AF burden was closely related to the efficacy of ATR A reduction in AF burden was more evident in those patients in whom ATP therapy efficacy was greater than 50% in terminating episodes. ATP efficacy was greater (52.6%) in episodes classified at onset as AT than in those classified at onset as AF (28.6%). ATP efficacy was also higher in patients with long pre-therapy P-P cycle interval and in patients with atrial lead implanted at the inter-atrial septum. Conclusion The present study demonstrates the safety and efficacy of automatic ATP therapies for terminating AT/AF with a sophisticated dual-chamber pacemaker. Atrial ATP terminated 36.9% of treated AT/AF episodes without any proarrhythmic effects in a population of patients with indications for pacemaker implantation and/or a history of AF (C) 2001 The European Society of Cardiology.