Title: Leadless Pacemakers in Post Operative Patients: Is It Time For the New to Become the Normal?

Invited Editorial: Manuscript ID JCE-23-0567.R2

Tyler P. Rasmussen, MD, PhD and E. Michael Powers, MD, MBA

University of Iowa Carver College of Medicine

Division of Cariology, Clinical Cardiac Electrophysiology

200 Hawkins Dr.

Iowa City, IA 52242

Edward-powers@uiowa.edu

Merchant et al. describe a single center retrospective analysis of leadless pacemaker (LP) implant following cardiac surgery or transcatheter valvular procedures that highlights the performance of LPs when implanted in patients with atrioventricular block (AVB) and either high risk features for conventional transvenous pacing or permanent atrial fibrillation (1). LPs performed well with a limited number of patients (7%) requiring conversion to transvenous pacing and only a single procedural complication. However, there was a statistically significant decline in left ventricular ejection fraction (LVEF) in the overall cohort. When subgroup analysis was performed, LVEF decline was only seen in those implanted with VVI devices but not in patients with VDD devices. Here, we discuss implications of this study.

Transcatheter aortic valve implantation (TAVI) is now more common than surgical AVR but carries a greater risk of high degree atrioventricular block (AVB) (~10%) (2,3). Cardiac surgery has been linked to a 1-3% risk of permanent pacemaker implantation with higher rates in patients undergoing valve replacement (4). Therefore, the number of patients at risk for AVB related to cardiac surgery and catheter-based valve interventions is increasing over time and warrants a critical evaluation of optimal pacing strategy.

Longitudinal registry data show that Micra (Medtronic, Minneapolis, MN) LPs have fewer required reinterventions and chronic complications compared to conventional transvenous pacing systems (5). Furthermore, mortality is comparable despite being implanted in patients with higher rates of end stage renal disease (ESRD) and medical complexity (5). LPs greatly outperform transvenous systems with respect to device related infections, as the rate of infection in LPs is trivial both short and long term (5,6). The risk of pacing induced cardiomyopathy (LVEF drop ≥ 10%) in pacemaker dependent patients is suggested to be equivalent or lower in those implanted with an LP (3%) versus those with a transvenous system (~13%) (7). A major drawback to the use of LPs is their inability to provide atrial pacing, which typically limits their use to patients without sinus node dysfunction.

The current paper demonstrates that the use of LPs is a viable strategy in post-operative patients. Their cohort included 50 patients having undergone cardiac surgery and 28 with a transcatheter valvular procedure (1). Of the 28 transcatheter procedures, 25 were TAVI. Factors prompting an LP implant versus transvenous were permanent AF, ESRD, tricuspid valve pathology, history of endovascular infection, and dermatological disease. Mean time from surgery to device implant was 7.3 ± 8.0 days, which suggests an adequate waiting period for AV conduction recovery in most circumstances. The only complication in the cohort (1.3%) was an access site hematoma requiring evacuation. Device parameters were stable at follow-up with a small but clinically insignificant decline in impedance and trivial rise in threshold, which is consistent with previously published data regarding Micra (6). The two major findings were that the pacing burden declined significantly in the follow-up period and that there was a significant reduction in the left ventricular ejection fraction (LVEF) in this cohort. Pacing percentages fell from mean 75% at implant to mean 48% at follow-up. The reduction in pacing burden suggests that many patients have late recovery in AV conduction post procedure. There was a drop in LVEF from baseline (55.0% ± 10.6%) versus follow-up (51.5% ± 11.2%, p =< 0.001), but this study is not designed to determine if the LVEF drop is because of the Micra or another unidentifiable factor. Importantly, the drop in LVEF was significant in the Micra VR group: baseline (54.1% ± 11.9%) versus follow-up (48.8% ± 11.9%, p = 0.003) but not in the Micra AV group: baseline (56.1 ± 9.0%) versus (54.6% ± 9.7%, p = 0.06). The only patient characteristic that was associated with a significant drop in LVEF (> 10%) versus those with stable EF was having a prior history of heart failure with a reduced ejection fraction. Taken together, this study showed that both Micra AV and VR can provide safe RV pacing in post-operative patients with a small, but significant risk for LVEF reduction that is likely linked to right ventricular pacing.