Optimizing atrial sensing parameters in leadless pacemakers: main findings of the OptiVALL study
Authors: Briongos Figuero S , Estevez Paniagua A , Sanchez A , Gomez Mariscal E , Jimenez Loeches S , Vaqueriza D , Munoz-Aguilera R 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.
Backgroung: The MARVEL2 study demonstrated the feasibility of leadless pacemakers in delivering atrioventricular (AV) synchronous pacing with an accelerometer-based algorithm, for up to 5 h.

Purpose
To assess the AV synchrony (AVS) the device can provide under daily activities and across different heart rate (HR) ranges, and to describe what programming changes are needed to achieve proper atrial tracking and AVS.

Methods
The OptiVALL study is a single-centre and prospective study of consecutive patients implanted with MICRA AV. Follow-up was routinely performed at 24 hours and at 1, 3, 6 and 12 months. The pacing mode was programmed to VDD in all patients and AV conduction mode switch (VVI +) was deactivated.
In each visit a device check was carried out and reprogramming of the atrial sensing parameters was performed according to the manual atrial mechanical tests, as well as information from device counters and rate histograms.
A 24-h Holter monitoring was placed at 3-months follow-up and ECG recorded tracings were automatically and blindly analyzed with an ECG delineation system. Cardiac cycles were defined as synchronous if a ventricular event followed the P-wave by ≤300 ms. AVS was calculated by dividing the number of synchronous cycles by the total number of cardiac cycles.
The primary efficacy endpoint was defined as AVS≥ 85% of total cardiac cycles during the 24-h Holter-ECG monitor. AVS was also calculated for each HR range of 10 bpm.

Results
Thirty-two patients (18 males, mean age 78.8 ±15.1, 16 patients with 3rd degree AV block, 15 patients with 2nd degree AV block, 1 patient with bifascicular block) underwent successful Micra AV implant, of whom 31 remained in VDD mode at some visit throughout the follow-up, and 26 remained in VDD mode at 3 months follow-up.
Device reprogramming of nominal parameters was needed in all patients at follow-up (table). The automatic A3 window end was disabled, and a fixed and short value was set in 100% of patients. Lower HR was set to 40 bpm in 88.5% (n=23) of patients. Auto A4 threshold and auto A3 threshold were modified in 6 and 3 patients respectively and vector was changed in 3 patients.
An ambulatory 24-h Holter monitor was performed 112.8±37.5 days after the implant in the 26 patients who remained in VDD. A comparison between nominal parameters and programming at ambulatory 24-h Holter monitoring is displayed in the table. Total ECG recorded time was 550.8 hours and 2,291,953 cardiac cycles were analyzed. Average ambulatory AVS was 87.3±6.3% (median: 87.6%) and 20 out of 26 patients showed an AVS≥85% of cardiac cycles.
AVS across the different heart rate ranges was good and remained ≥85% until 90 bpm (figure) with a substantial drop only with HR over 110 bpm.

Conclusions
High ambulatory AVS in outpatients with leadless pacemakers can be feasible, although may require manual reprogramming of atrial sensing parameters, especially the A3 window end setting.