Predictors of long-term atrioventricular synchrony with leadless Micra AV pacemaker: insights from a real-world cohort
B Jacobs, T Van Weyenbergh, A Bohyn, R Willems, A Van De Bruaene, B Vandenberk, C GarwegAbstract
Background
Ventricular leadless pacemakers reduce lead- and pocket-related complications but provide only ventricular pacing. The Micra AV extends this concept by achieving atrioventricular synchrony (AVS) through accelerometer-based sensing of atrial contractions. Real-world AVS remains variable, and the baseline predictors of atrial sensing amplitude (A4) and long-term AVS remain unclear.
Purpose
We aimed to identify clinical and echocardiographic predictors of A4 amplitude (at implantation) and 12-month AVS in patients requiring ≥80% ventricular pacing.
Methods
Baseline clinical and echocardiographic data were collected in 94 consecutive patients implanted with a Micra AV between June 2020 and November 2023. Echocardiographic parameters included mitral inflow and annular tissue Doppler, left and right atrial strain, strain rate and volumes, LV global longitudinal strain, TAPSE, and RV longitudinal strain and strain rate. A4 amplitude was measured at first device interrogation post-implant, and 12-month AVS was evaluated in the subgroup with ≥80% ventricular pacing. Predictors of A4 and AVS were identified using MI-LASSO and a forward stepwise majority-and-Wald approach with internal bootstrap validation. Predictors were categorized as "consistently-selected" (retained in both models, significant in at least one) or "model-specific" (retained and significant in only one model).
Results
Median age was 80 [78–84] years, 35% were female, and 77% had arterial hypertension (AHT). Thirty-eight patients (43%) exhibited ≥80% ventricular pacing (median AVS index 90% [IQR 80–99]). As shown in Table 1, predictors of A4 amplitude included AHT, no prior cardiac surgery, higher TAPSE (all consistently-selected), and atrial function quantified by reservoir strain and conduit strain rate (model-specific). Predictors of AVS at 12 months were age, left atrial reservoir strain rate, lower right atrial end-systolic volume index (RAVi) - all consistently-selected -, and lower E/E′ (model-specific). The final models explained up to half of the variance in A4 (R² = 0.55, 95% CI 0.41–0.68) and most of the variance in AVS (R² = 0.80, 95% CI 0.61–0.92).
Conclusion
A4 amplitude, essential for AVS, was higher in patients without prior cardiac surgery or with AHT, consistent with preserved atrial function and greater reliance on atrial contraction in early diastolic dysfunction. Higher AVS at one year in older patients, may similarly reflect greater atrial contribution with reduced ventricular compliance, together with less motion-related signal interference. Echocardiographic predictors mirrored these mechanisms: preserved left atrial strain and strain-rate indices correlated with higher A4 and AVS. In contrast, markers of elevated filling pressures (E/E′ and RAVi) correlated with lower AVS, consistent with reduced late atrial filling. Collectively, these results provide a physiological basis for identifying patients most likely to benefit from Micra AV implantation.