Trajectory analysis of lead impedance and capture threshold for early detection of pacemaker lead dysfunction

Introduction

Progressive or abrupt variations in lead impedance and capture threshold are recognised indicators of conductor fracture, insulation failure, or electrode–tissue interface changes. Yet, current follow-up relies on static cut-offs rather than patient-specific longitudinal behaviour. Quantifying individual trends may enable earlier detection of subclinical lead dysfunction before alarm thresholds are reached. This study evaluated whether annual trajectories of impedance and capture threshold predict electrical alerts and subsequent lead revision in permanent pacemaker patients.

To determine whether annual slopes of impedance (Ω/year) and capture threshold (V/year) independently predict electrical alerts and to assess their relationship with subsequent device revision or replacement.

Purpose

A retrospective longitudinal analysis included 1,469 pacemaker patients and 16,655 follow-up visits from 2016 to 2025. Patients with ≥3 valid controls (n=1,207; mean age 73±10 years; 58% male) were eligible for trajectory analysis. For each lead (atrial, right and left ventricular), impedance and capture threshold were standardised, and annual slopes derived by linear regression per patient. Electrical alerts were defined as impedance changes >200 Ω or threshold increases >0.4 V between consecutive visits. Event-free survival was analysed by slope tertiles with Kaplan–Meier curves and log-rank tests. A multivariable Cox model including both slopes (standardised) assessed their independent predictive value.

Results

A total of 2,842 leads (41% atrial, 52% right ventricular, 7% left ventricular) were analysed. Median slopes were −13.2 Ω/year (IQR −30.1 to −2.8) and −0.02 V/year (IQR −0.06 to 0.03). During 28 months of median follow-up (IQR 15–46), 212 patients (17.6%) experienced ≥1 electrical alert. Event-free survival declined progressively across impedance and threshold tertiles (p<0.01 for both). At 24 months, cumulative incidence was 22.9% for the highest impedance slope and 20.1% for the highest threshold slope. Patients in the upper tertiles for both parameters had a two-fold higher event rate (28.6% vs 14.9%; HR 2.07, 95% CI 1.24–3.44, p=0.004). Among those with alerts, 48% underwent device revision or generator replacement (9% of total), usually within 60 days. Both slopes remained independent predictors: impedance HR 1.41 (95% CI 1.05–1.88, p=0.02); threshold HR 1.36 (95% CI 1.02–1.80, p=0.03).

Conclusion

Longitudinal trajectories of impedance and capture threshold were independently associated with early electrical alerts and device revisions. Positive slopes identified high-risk patients even when absolute values remained within nominal ranges. Combined trajectory analysis doubled the probability of early alerts, supporting a transition from reactive to predictive device surveillance. This reproducible metric could be integrated into remote monitoring systems and warrants prospective multicentre validation.