Programming VDD leadless pacemakers: relation of algorithm settings of A3 and A4 signals with atrioventricular synchrony
Authors: Estevez Paniagua A , Briongos Figuero S , Sanchez Hernandez A , Munoz Aguilera R 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
The development of VDD mode in leadless pacemakers (Micra AV) has allowed the use of leadless pacing in patients with an atrioventricular (AV) block. Keeping AV synchrony (AVS) on pacing improves cardiac output and quality of life and reduces the risk of atrial fibrillation (AF) and PM syndrome. The AVS of the pivotal study with Micra AV (MARVEL2), in a post-implant situation of low activity was 89%.

Methods
Prospective single-center study of consecutive patients who received a VDD leadless pacemaker (Micra AV), and who remained in VDD mode throughout the follow-up. The initial programming changes were conducted following the standard recommendation for problems resolution, and further changes were made based on experience. Univariate association was tested for different programming parameters with the percentage of AVS. Our goal was to find the best possible programming for the Micra AV pacemaker with the scope of achieving high percentages of AVS in real life.

Results
We included 26 patients who received a VDD leadless pacemaker (Micra AV) between Jun/20 and Nov/21 and were kept in VDD mode at least during the first month of follow-up. We made an intermediate analysis from the first 18 patients who reached the first month after implant, and a significant association was found between the adjustment of the end of the window of A3 (VE) with the percentage of AVS: in the group in which automatic VE adjustment was maintained after implantation (4 patients), the mean AVS was 76.9 ± 6.0% (VE 702± 60 ms), while in the group in which the automatic adjustment was deactivated and the VE was set at 600-650 ms (14 patients), AVS was 84.9 ± 7.2% (VE 614 ± 23 ms), p = 0.04 (Figure 1). When discriminating by AVS ≥ 85%, the deactivation of the automatic adjustment of VE had an OR of 5.6 compared to maintaining automatic adjustment (p = 0.018), with a χ2 of 4.1 (p = 0.043). Moreover, when we analyzed the data until the sixth month of follow-up for those patients in VDD mode, we found that the shorter the interval of VE window we programmed, the larger the AVS percentage was (1st month, 26 patients: VE 631±46 ms, AVS 83.8±6.9%; 3rd month, 24 patients: VE 621±35 ms, AVS 86.2±6.6%; 6th month, 19 patients: VE 614±25 ms, AVS 88.3±6.5%, p&lt;0.001; Figure 2).
On the other side, there was no significant association between the modification of the A4 threshold (p = 0.104), adjustment of the rate smoothing (p = 0.331), or signal vector change (p = 0.276) with the percentage of AVS.

Conclusions
In real life, AVS percentages can vary considerably from the data obtained in resting situations and short follow-up time. Even though our series is not extensive, the preliminary data suggest the importance of adding modifications in the standard programming, especially in the algorithm for adjusting the A3 window, altogether with the standard recommendations for problem-solving to achieve high AVS percentages.