Mechanism of Acute Pacing Threshold Elevation During Simultaneous Micra
Leadless Pacemaker Implantation and AV Node Ablation
Abstract
Background In patients with refractory atrial fibrillation
(AF), atrioventricular nodal (AVN) ablation and permanent pacemaker
implantation is recommended. The Micra Transcatheter Pacing System™
(Micra) is a single chamber leadless pacemaker (LPM) and thus offers the
possibility of AV node (AVN) ablation in the same procedure. Pacing
threshold (PT) elevation after radiofrequency (RF) ablation is a
potential complication. Methods We conducted a single center
retrospective cohort study. All patients implanted with a Micra (n=84)
and concomitant or delayed AVN ablation (n=12) from 2014 to 2022 were
included. We describe two cases of acute Micra PT elevation immediately
following RF AVN ablation requiring device retrieval and implantation of
a new Micra. Procedural characteristics and electrophysiological
parameters were analyzed, and computer modelling was performed to
determine factors responsible for acute PT elevations. Results
A total of 84 patients were included. Mean age was 74±10 and 48% were
women. Twelve patients (14%) underwent AVN ablation. Two patients had
acute PT elevation requiring device retrieval despite no direct contact
of the ablation catheter with the Micra. Computer modelling shows that
significant dissipated power due to electrical field coupling can occur
at the tip or ring electrode if the catheter is not kept at a safe
distance (≥15 mm) from the Micra. Conclusion Concurrent AVN
ablation and Micra implantation is safe in most patients. To prevent
acute PT elevation, keeping a safe distance of ≥15 mm from the tip and
ring electrodes of the Micra and using lower power output may prevent
this complication.