Association between current of injury and intraoperative R wave amplitude fluctuation immediately after active fixation pacing lead implantation

Abstract Background Active fixation lead stability and pacing threshold adequacy are predictable from assessment of current of injury (COI) prevalence. However, time courses of R wave amplitude value immediately after implantation varies despite of COI prevalence. Objective This study aims to clarify whether intraoperative R wave amplitude fluctuation is associated with COI, and the adequacy assessment is possible. Methods Consecutive recipients of active fixation lead implanted to right ventricular (RV) septum from April to November 2023 were enrolled. R wave amplitude values automatically measured by programmer were continuously recorded from immediately after implantation to generator connection. The final R wave amplitude value greater than 4 mV was determined as implantation success. The successful implantation time courses of R wave amplitude value classified into following three types (Figure 1): (1) the Dipper type; R wave amplitude transiently decreases to the bottom value and then increases, (2) the Riser type; R wave amplitude shows a upward trend (no decline) for the first 5 minutes after active fixation, and (3) the other type. The primary outcome was prevalence of favorable amplitude increase defined as the final R wave amplitude value exceeding that of immediately after the active fixation. Results Among 106 of RV lead implantations in 78 consecutive pacemaker recipients, 73 successful implantation records were evaluated (5 missing data and 28 unsuccess implantations). According to the continuous R wave amplitude records, 51 and 19 successful implantation time courses could be classified into the Dipper and Riser types, respectively. In the Dipper type, the median screw-in to bottom time (SBT) was 5 (interquartile range: 5–12) minutes, and then R wave amplitude improved to mean of 1.7 ± 0.6 times higher than the bottom value. The electrogram (EGM) immediately after active fixation showed R wave < COI pattern, and gradually changed to R wave > COI pattern by the withdrawal of COI over time. Among them, 26 implantations showed favorable amplitude increases and significantly shorter SBT than the remaining implantations (6 ± 4 minutes vs. 10 ± 5 minutes, P=0.03). The ROC analysis showed the predictive cut-off value of SBT for favorable amplitude increase was 6 minutes (AUC:0.73, sensitivity:0.81, specificity:0.60). In the Riser type, acceptable R wave amplitude and R wave > COI pattern EGM were consistently recorded, and finally obtained the favorable amplitude increase in all implantations. Conclusion More than 95% of R wave amplitude fluctuation patterns immediately after successful lead implantation could be classified as the Dipper or Riser types. The mechanism might be associated with a competition among R wave amplitude and COI magnitude, and the prediction of favorable R wave amplitude increase might be possible by the EGM patterns obtained immediately after active lead fixation and the subsequent 5–6 minutes of observation.Success implantation time coursesClinical implication