Real-world data suggests that successful VDD pacing during higher sinus rates in the outpatient setting was more difficult than results of initial feasibility studies indicated. These findings were published in Heart Rhythm.

This investigator-initiated observational study was conducted in 2020 and 2021 at the Bern University Hospital in Switzerland. Patients (N=20) with a pacemaker (PM) indication in sinus rhythm without need for atrial pacing who received a leadless PM programmed to VDD mode (MicraÔ AV, Medtronic) were included in this study. Atrioventricular (AV) synchrony, defined as QRS complex preceded by a p-wave within 300 ms, was evaluated by Holter electrocardiography up to 3 months after implantation.

Patients were aged median 80 (IQR, 76-86) years, 55% were women, BMI was 25.7 (IQR, 24.5-30.3), 75% had arterial hypertension, and left ventricular ejection fraction was 60% (IQR, 55%-64%).


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The indications for PM were intermittent third-degree atrioventricular block (AVB; 55%), permanent third-degree AVB (15%), symptomatic second-degree AVB (10%), left bundle branch block with first-degree AVB (10%), intermittent high-degree AVB (5%), and carotid sinus syndrome (5%).

Ventricular pacing was relatively low (mean, 21.6%; median, 0%). At the first postoperative follow-up, the median AV synchrony (³80% ventricular pacing) was 29%, increasing to 40% at the second optimization session (P =.038).

AV synchrony was negatively correlated with the intrinsic sinus rate during predominantly paced episodes (P <.001), in which when sinus rates were 50 to 80 per minute median AV synchrony was 91% and at over 80 per minute, it was 33%.

Loss of AV synchrony was observed during premature beats, intermittent p-wave, undersensing, reverse AV conduction mode switch, tracking check function, and sinus rates lower than programmed rate events.

Predictors for high AV synchrony included minimum A4 threshold (b, -5.235; 95% CI, -7.285 to -3.185; P <.001), maximum A3 window end (b, -0.002; 95% CI, -0.004 to -0.001; P <.001), and A3 threshold (b, -0.044; 95% CI, -0.088 to -0.001; P =.046).

The self-diagnostic data from the PMs indicated that AV synchrony correlated with a high rate of ‘AMVS’ (T, 0.12; P <.001), ‘VS only’ (T, 0.32; P <.001), ‘VP only’ (T, -0.38; P <.001), and ‘AMVP’ (T, -0.33; P <.001).

The findings in this study may have been biased by not considering patient health or adaptation to drug regimen.

“AV synchrony in outpatients with leadless VDD PMs who require a relevant amount of pacing is substantially lower than might have been expected from early feasibility studies on leadless VDD pacing,” the study authors wrote. “Leadless VDD PMs often require multiple reprogramming to maximize AV sequential VDD pacing and yet still may have a low percentage of AV synchrony, especially with increased heart rates.”

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Neugebauer F, Noti F, van Gool S, et al. Leadless atrioventricular synchronous pacing in an outpatient setting: Early lessons learned on factors affecting atrioventricular synchrony. Heart Rhythm. Published online December 28, 2021. doi:10.1016/j.hrthm.2021.12.025