Strategies to improve atrioventricular synchrony in patients with a Micra AV leadless pacemaker

Abstract

The second generation of transcatheter pacing systems, called Micra AV, can provide atrioventricular (AV) synchronous pacing via a new pacing algorithm relying on sensing mechanical atrial contraction. Several novel programming parameters were introduced to enable AV synchronous pacing, including an A3 window and A4 window as well as a conduction mode switch and an activity mode switch. In addition to several automated features, manual programming optimization of some of the novel parameters is key to improving AV synchrony. A solid knowledge of the features and their programming is essential for electrophysiologists implanting or following patients with Micra AV devices. Differences in programming optimization might partially explain the high variability of AV synchrony published in real-world data reports. This article reviews the key programming parameters of Micra AV. Subsequently, optimal programming recommendations for defined patient profiles are presented. Those were established by consensus within an expert panel comprised of 11 European electrophysiologists from high-volume Micra AV centres. The patient profiles were (1) high degree AV block and slow sinus rhythm; (2) high degree AV block and fast sinus rhythm; and (3) intermittent AV block. The panel recommended to evaluate the mechanical atrial activity on transthoracic echocardiography prior to implant. It was also agreed that Auto A3 Threshold and Tracking Check should be turned off in all patients, AV conduction mode switch should be turned off in all patients with high degree AV block, and the lower rate should be programmed to 50 bpm with exceptions based on individual clinical assessment. Future studies will be useful to evaluate the strength of those recommendations to improve the AV synchrony.

Keywords: AV synchrony; Leadless pacemaker; Patient selection; VDD pacemaker.

Graphical Abstract

Figure 1

(A) The four different accelerometer signals. (B) Specific Micra AV parameters and adapted programming parameters.

Figure 2

General recommendation for Micra AV patients’ management.

Figure 3

(A) Micra AV general programming recommendations. (B) Micra AV specific programming recommendation for different patients’ profiles.

Figure 3

(A) Micra AV general programming recommendations. (B) Micra AV specific programming recommendation for different patients’ profiles.

Figure 4

Auto A3 Threshold. The auto A3 threshold adjusts its maximal value on the maximal A3 amplitude sensed across the latest 24 h. (A) At lower rates, separate A3 and A4 signals can be well-identified. (B) At higher rates (typically >85/min), the A3 and A4 signals summate creating an A7 signal. (C) Example of the undersensing that can occur when the Auto A3 Threshold adjusts the A3 threshold too high.

Figure 5

Auto A3 Window End. A Manual Atrial Mechanical test shows here an A3 window end that is set too short. This can result in oversensing the A3 signal in the A4 window.

Figure 6

Illustration of the activated ‘tracking check’ feature at fast sinus rhythm. To guard against oversensing in the A3 window, tracking check extends PVARP for 1 cycle, causing the next cycle to fall within the refractory period (arrow).