Figure 3: A: Pacing from the EIS catheter demonstrating a “w” pattern with a notch at the nadir of the QRS in lead V1, and discordant QRS morphology in the inferior leads (R in II taller than III), and in leads aVR/aVL(negative in aVR, positive in aVL). B: Unipolar recording of Left Bundle Branch potential in the lead (Po LBB). C: Stimulus-peak Left Ventricular Activation Time (Stim-LVAT) of 67 ms is constant at both high and low outputs. D: V6-V1 interpeak interval of 35 ms is recorded during non-selective LBB capture6. E: Left Anterior Oblique view (LAO 30°) septogram demonstrating depth of septal penetration of the lead. F: Final Anterior-Posterior (AP) view of the right atrial and LBB pacing leads.