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. 2021 Jun 14;8:674452. doi: 10.3389/fcvm.2021.674452

Figure 1.

Figure 1

Twelve-lead ECG and intracardiac electrogram (EGM) in a patient. The native cardiac rhythm (A); twelve-lead ECG by right ventricular pacing (RVP) (B); the ECG by left bundle branch pacing (LBBP) (C); narrow ECG QRS with LBB potential in intracardiac electrograms (EGM at the bottom) in a infranodal atrioventricular block (AVB) patient (D). His bundle pacing (HBP) could not pace beyond the block site (2.5 V at 0.4 ms) (E). Selective (0.6 V at 0.4 ms) and non-selective (0.5 V at 0.4 ms) LBBP (F) and the angiogram of the sheath to assess the depth of the LBB LBBP lead (G) are shown. Echocardiography showed the lead was fixed in the left ventricular septum (H), and LBBP but not HBP could pace beyond the block site in one patient of AVB with infranodal block. HBP at 2.5 V/0.4 ms could induce the loss of capture (2:1) (E), while LBBP could induce pacing (1:1) (F), indicating LBBP but not HBP could pace beyond the block site in infranodal AVB patients. His and LBB potential were seen in the pacing location (D).