Proarrhythmic effects from competitive atrial pacing and potential programming solutions.

BACKGROUND Programmed long AV delays and intrinsic long first degree AV block may increase risk for competitive atrial pacing (CAP) in devices without CAP avoidance algorithms. METHODS Patients identified with CAP-induced mode switch episodes were followed clinically from 9/2013 to 08/2019. Attempts to avoid CAP included shortening of post-ventricular atrial refractory period (PVARP) or post ventricular atrial blanking period (PVAB), or change to AAI or DDI modes. After observing associations with sensor-driven pacing, rate-response was inactivated in a subset. RESULTS Among 23 patients identified with CAP (22 St. Jude Medical [Abbott]; 1 Boston Scientific Corporation devices), atrial fibrillation (AF) was induced in 12 (52%), lasting 10 seconds to 28 hours and 32 minutes. In one patient with an ICD CAP induced AF with rapid ventricular rates that triggered a shock, inducing ventricular fibrillation, syncope and another shock. Changing AV delays and shortening of PVARP failed to resolve CAP. After noting that all had CAP during sensor-driven pacing, rate response was inactivated in 7, resolving further device-induced AF in the 3 of 7 that had prior CAP-induced AF. In 2 patients with intact AV conduction, AAI(R) pacing resolved further documentation of CAP. CONCLUSIONS CAP predominantly occurs during sensor-driven atrial pacing that competes with intrinsic atrial events falling in PVARP. Inactivation of the activity sensor or change to atrial-based pacing modes (AAI/R) appears to effectively prevent induction of device-induced atrial proarrhythmia. Ultimately a corrective algorithm is needed to avoid CAP-induced proarrhythmia. This article is protected by copyright. All rights reserved.