2.2. Lead implantation

LBBP was achieved by a transventricular septal method in the basal ventricular septum as described elsewhere. 7 Briefly, the Select Secure (model 3830, 69 cm, Medtronic Inc, Minneapolis, MN) pacing lead was introduced through a fixed curve sheath (C315 HIS, Medtronic Inc) toward the right ventricle beyond the tricuspid annulus. During the procedure, the His bundle region was identified as an anatomic marker before further advancing the lead toward the cardiac apex by 1.0 to 2.0 cm. Once the paced QRS morphology showed a “W” pattern in V1, the lead was perpendicularly screwed in. When screwing, the unipolar electrode pacing pattern and impedance were consecutively monitored. The lead was finally fixed when the paced QRS morphology showed a “QR/Qr” pattern in V1, and the stimulus to left ventricular activation time (stim‐LVAT) was the shortest and consistent during high and low outputs in V5 or V6. 8 The right atrial lead was implanted in the right atrial appendage and connected to the atrial port. The LBBP lead was connected to the ventricular port if a dual‐chamber pacemaker was implanted. For patients who failed in LBBP, right ventricular septal pacing (RVSP) was performed as an alternative. The LV leads were implanted in the lateral or postlateral left ventricular vein if possible as mentioned elsewhere. 9 In patients with normal sinus rhythm undergoing CRT‐pacemakers(P), the LBBP lead was connected to the right ventricular (RV) port and the left ventricular (LV) lead to the LV port. In patients with normal sinus rhythm undergoing CRT‐defibrillators(D), the LBBP lead was connected to the LV port and an implantable cardioverter‐defibrillator lead was implanted in the RVA and connected to RV port.