The threshold question: what baseline electrical parameters could predict optimized atrial septal lead stability?
K Abdelsayed, M Kapphahn-Bergs, M Desouki, D Witt, J Sengupta, M OlsonAbstract
Background
Unlike the conventional atrial appendage leads, the lumenless atrial septal leads are narrow caliber, steroid-eluting, actively fixating leads minimizing tissue trauma. While these design differences enhance electrical stability, long-term predictors of threshold for atrial septal leads remain unclear. Progressive threshold rise expedites battery depletion and with early generator replacement or lead revision. Capture threshold and impedance are key electrical markers of electrode–myocardial interface integrity, but their baseline values and temporal trajectories, and how they jointly predict clinically meaningful threshold rise, have not been well-studied.
Objective
We aim to provide valuable data on the relationship of baseline electrical parameters to with threshold progression to inform more optimal implantation characteristics.
Methods
This retrospective study included adults ≥18 years who had atrial septal leads implanted at one of two tertiary referral centers within a large Healthcare System (January 2019-April 2024). Postimplant threshold voltage and impedance were recorded within three months and during yearly follow-up for five years. Logistic regression estimated (1) the probability of capture threshold exceeding 2.0 V and (2) the probability of ≥1.0 V increase from baseline, both within 2 years. Predicted probabilities across the spectrum of baseline parameters were visualized using color-coded probability surfaces. Longitudinal scatter plots with regression analysis evaluated the correlation between changes in impedance and threshold over time.
Results
A total of 443 patients were included (age: 76 years, 56% males, BMI: 28.7). Mean follow-up was 21.3 months. Threshold exceeded 2.0 V in 18 patients (4.1%), while 5.2% experienced a ≥1.0 V rise from baseline within 2 years. Baseline threshold voltage seemed to be the strongest predictor of clinically significant rise above 2.0 V, with risk increasing steeply beyond 1.6 V regardless of impedance. The risk still increased with lower baseline threshold values when baseline impedance was <550 Ω (Fig-1A). Conversely, threshold drift of ≥1.0 V was almost exclusively associated with a low baseline impedance (<550 Ω) (Fig-1B). Finally, the longitudinal analysis demonstrated a persistent positive correlation between impedance and threshold changes across follow-up, suggesting shared interface-related mechanisms (Fig-2).
Conclusion
Postimplant high threshold voltage >1.6V was the main predictor of major threshold escalation above 2V within two years post-implantation of atrial septal leads, while baseline impedance <550 Ω predicted smaller dynamic drifts >1V. Future studies on larger cohorts should validate the benefits of a combined post-implant threshold and impedance cutoffs of <1.6V and >550 Ω, respectively. Moreover, monitoring the longitudinal increase in impedance trends may identify patients at risk for threshold instability and guide proactive device management.Figure 1Figure 2