Association Between Current of Injury Magnitude and Intraoperative R-Wave Amplitude Fluctuation After Pacing Lead Implantation

BACKGROUND: Pacing threshold adequacy and lead stability can be predicted from the magnitude of the current of injury (COI) immediately after active fixation. However, intraoperative R-wave amplitude often fluctuates despite sufficient COI. OBJECTIVES: The authors aimed to assess whether R-wave amplitude fluctuations are associated with the COI magnitude and can be predicted from early electrogram (EGM) patterns. METHODS: EGMs of 109 cases of right ventricular pacing on the septum were continuously recorded from implantation to generator connection. R-wave amplitude fluctuation patterns were categorized as Dipper type (transient decrease followed by an increase), Riser type (continuous increase), and Other type. The primary outcome was a favorable R-wave amplitude increase, defined as the final value exceeding the initial value. RESULTS: Among the 109 cases, 65 (60%) exhibited Dipper-type and 41 (38%) showed Riser-type R-wave fluctuation patterns. In the Dipper-type patterns, initial EGMs showed R-wave amplitude < COI, which subsequently shifted to R-wave amplitude > COI patterns. Favorable amplitude increases occurred in 34 (52%) of the Dipper-type cases and were associated with shorter times to the lowest R-wave amplitude, with 6 minutes being identified as optimal for prediction (sensitivity: 0.82, specificity: 0.61). All the Riser-type patterns exhibited favorable amplitude increases, with consistent R-wave amplitude > COI patterns. CONCLUSIONS: Most intraoperative R-wave amplitude fluctuations in successful lead implantations follow Dipper- or Riser-type patterns. Favorable R-wave amplitude increases can be predicted within 6 minutes post fixation using early EGM patterns.