LAUSR

Introduction Leadless pacing is an alternative to transvenous single-chamber ventricular pacing (VVI/R) with a favorable safety and efficacy profile in selected patients. Until recently, the Micra (Model MC1VR01; Medtronic Inc, Minneapolis, MN) was the only leadless pacing system approved for clinical use in the United States. The leadless pacemaker is an attractive option for patients with permanent atrial fibrillation who require infrequent ventricular back-up pacing and in those in whom atrioventricular (AV) synchrony is not pursued, especially when vascular access is limited (ie, hemodialysis patients) or the risk of intravascular infection is deemed high. The recently approvedMicra AV (Model MC1AVR1; Medtronic Inc) represents a major development in leadless pacing technology. Micra AV uses its accelerometer to sense the atrial mechanical events and deliver leadless AV-synchronous ventricular pacing (VDD). The Micra AV therefore has the potential to provide VDD pacing with a lower rate of pocket/lead-related complications vs transvenous systems. Pacing-facilitated ventricular arrhythmias have previously been reported after Micra implantation. Here, we report the first case of bradycardia-dependent polymorphic ventricular tachycardia (PMVT) caused by atrial undersensing in a patient implanted with the Micra AV leadless pacemaker.