Pacing parameters and 12-lead ECG characteristics
The intraoperative pacing capture threshold was moderately lower in the radiography group (0.48 ± 0.17 V @0.25 ms) than in the non-radiography group (0.58 ± 0.30 V @0.24ms, P =0.046). Location-based pacing capture threshold was 0.48±0.16V@0.24ms in zone 2 of the septum, 0.62±0.19V@0.24ms in the superior septum, and 0.25±0.00V@0.24ms in the inferior septum (P =NS among three locations). Pacing impedance was 966.2 ± 260.9 in the non-radiograph group and 887.8 ± 234.6 Ω in the radiography group (P =0.169 between two groups), and sensed R-wave amplitude was 10.6 ± 4.0 mV in the non-radiography group and 10.3 ± 4.3 mV in the radiograph group (P =0.786 between two groups).
A relatively narrow paced QRS duration and short left ventricular activation time were observed in the radiography group and the non-radiography group (Table 3). Based on the location of the MicraTM pacemaker, the QRS duration and left ventricular activation time appeared slightly, but not statistically significantly, narrower and shorter for MicraTMpacemaker location in septal zone 2 (the mid-septum) than in other septal locations (Table 3). Figure 4 shows examples of the 12-lead ECG morphology in these three septal locations.