Prevalence, characteristics and clinical implications of regular atrial tachyarrhythmias in patients with atrial fibrillation: Insights from a study using a new implantable device

Objectives This study prospectively analyzed atrial tachyarrhythmia (AT) or ganization and antitachycardia pacing (ATP) success in patients with an imp lanted device for AT therapy. Background In patients with atrial fibrillation (AF), the incidence of regu lar, slow ATs emendable by ATP is unknown. Methods Forty patients with previously documented AT (70% with AF) received a new pacemaker with atria! electrogram (AEG) storage and atrial ATP capab ilities fur standard pacing indications. The AEGs acquired during the first month (study phase 1) were classified into high (type I), intermediate (ty pe II) and low (type III) degrees of organization. Atrial ATP was then acti vated, and treated AT episodes were retrieved three and six months after im plantation (study phase 2). Results Of 824 AEGs retrieved before ATP activation (study phase 1), 351 (4 3%) were classified as type I 47% as type II and 10% as type III. Episodes of AT starting as type I (35%) and type II or III (65%) maintained their ty pe over 1 min in 73%. All patients with an exclusive history of AF also sho wed type I AEGs. In 361 subsequently treated AT episodes (study phase 2), A TP was successful in 62% of type I and 34% of type II episodes, but not in type III (p < 0.0001). Conclusions The majority of patients with a history of AF shorn not only di sorganized but also highly organized AT episodes, which can be successfully terminated by ATP. (J Am Coll Cardiol 2001;38:355-63) (C)2001 by the Ameri can College of Cardiology.