Abstract 13903: Pacemaker Mediated Arrhythmia Following AV Synchronous Leadless Pacemaker Implantation

Abstract

Background: Leadless pacemakers have gained popularity in providing permanent pacing in select patient populations. Pacemaker mediated tachycardia and arrhythmias have been well described in patients with dual chamber pacemakers, but up to this point not in leadless pacing. Case Description: A 91-year-old female with symptomatic bradycardia and 2:1 AV block underwent implantation of a Micra AV pacemaker programmed VDD 60-100 bpm. Five months later, she presented with decompensated heart failure with a heart rate of 88 bpm and a newly reduced left ventricular ejection fraction of 30%. Device interrogation showed 95% ventricular pacing, with 91% AV synchrony. The Micra was found to be tracking an atrial rhythm between 80-100 bpm more than 80% of the time (Figure 1A). RV pacing induced cardiomyopathy was suspected and she underwent placement of a bi-ventricular pacemaker. During implant, a short VA time was noted and changes in the V-V cycle length predicted changes in the A-A cycle length (Figure 1B). Micra ventricular pacing was held resulting in an AV paced rhythm from the CRT system and a drop in rate to 60 bpm (Figure 1C). These results indicate that the Micra pacemaker was tracking the atrial mechanical contraction (AM) from a retrograde conducted P-wave resulting in elevated heart rates from a pacemaker-driven arrhythmia. Discussion: In patients with poor AV conduction, intact VA conduction, and SA node dysfunction, Micra AV may create pacemaker mediated arrhythmia by tracking the AM of the retrograde conducted P-wave. Careful patient selection to avoid Micra AV placement in patients with SA node dysfunction, and close attention to the rate histogram on device interrogation may prevent development and facilitate recognition of this unique cause of pacemaker-mediated arrhythmia.