Upgrading a single-chamber leadless pacemaker to a dual-chamber leadless pacemaker system
Authors: Bongiorni M G , Reddy V Y , Ip J E , Doshi R , Exner D V , Defaye P , Canby R , Shoda M , Hindricks G , Rashtian M , Neuzil P , Ganz L , Harbert N D , Bulusu A , Knops R E 
Published: May 2024

Abstract

Background/Introduction
The first global dual-chamber leadless pacemaker (DR-LP) study included a group of subjects with a pre-existing upgradeable ventricular single chamber leadless pacemaker (VR-LP) in whom the addition of an atrial leadless pacemaker (AR-LP) was undertaken to allow upgrading to a dual chamber leadless pacing (DR-LP) system.

Purpose
Summarize success rates of single to dual chamber leadless pacemaker upgrades, as well as device and i2i throughput measurements, serious adverse device effects (SADEs) and mortality in this cohort.

Methods
Subjects with a pre-existing VR-LP who were indicated for a dual-chamber pacemaker were included. Upgrade procedures included downloading firmware to existing VR-LP, placing AR-LP, and pairing the devices to operate in a DR-LP mode. Electrical and i2i throughput measurements were collected at implant, pre-discharge, 1-mo, 3-mo, 6-mo, and 12-mo. Upgrade success rate was defined as an AR-LP upgrade procedure that resulted in a functional DR-LP system. SADEs included all reported events that were adjudicated as serious and possibly, probably or causally related to the procedure or system. SADEs and deaths were adjudicated by an independent clinical events committee.

Results
Out of 36 enrolled subjects (61.1% male, 70.4 ± 13.8 yrs., 55.6% sinus node dysfunction, 38.9% AV block), 35 had an attempted implant, and 32 of these were successful (91.4%). The 3 unsuccessful upgrade attempts were related to unsuccessful placement of the AR-LP due to complications during the procedure (n = 2) or an inability to implant an AR-LP (n = 1). Figure 1 illustrates a declining early mean pacing capture threshold, rising early P-wave amplitudes, and stable impedance for the AR-LP over the 12 months. Mean i2i throughput for communication from the RV to RA and the RA to RV improved from pre-discharge to 3 months and remained stable through the subsequent 9 months (Figure 2). A total of 5 subjects (5 of 36; 13.9%) experienced 7 SADEs (all procedure-related; 2 related to the AR-LP and 2 to the delivery catheter). One non-cardiovascular, non-device, non-procedure related death occurred in the upgrade population.

Conclusions
The single to dual-chamber upgrade cohort demonstrated a high upgrade success rate (91.4%), stable atrial and ventricular electrical measurements and consistently high i2i communication throughout the 12 months. AV synchrony (AVS) was not specifically measured in this upgrade cohort, but data from the main DR-LP study suggest that i2i throughput correlates with, but significantly underestimates AVS. Further, the rate of complications was acceptable (13.9%) and limited to the procedure. These data confirm the feasibility, safety and longer-term effectiveness of adding an atrial LP in patients with a pre-existing ventricular LP order to achieve effective dual chamber pacing.Fig. 1: Upgrade Electrical measurementsFig. 2: i2i communication for Upgrades