2.2 LBBAP surgery
In this study, all the pacemaker implantations were performed through the left subclavian vein or the left axillary vein. During surgery, a C315 His sheath was inserted into the tricuspid ring using a J-wire. In the right anterior oblique position (RAO), the pacemaker electrode (Model 3830, 69 cm, Medtronic Inc., Minneapolis, MN) was pushed forward through the sheath, with the distal screw located at the tip of the catheter. First, the His potential was marked, and the tip of the pacing lead was moved downward and forward in the ventricular direction for approximately 1.5-2 cm. Subsequently, the optimal pacing site was determined by the following criteria: a) the pacing QRS interval was less than 145 ms in the V1 lead, or the QRS wave had a “W” incisura in the V1 lead; b) the left anterior oblique position confirmed that the tip of the pacing lead reached the left ventricular septum intima; c) recording to the left bundle branch potential (from scratch and small to large); d) the pacing pattern gradually changes from the LBBB to the RBBB pattern[7]. Finally, the electrode was fixed and connected to the pacemaker using the screws. In this study, we detected the pacing threshold, recorded the left bundle branch potential, monitored the pacing impedance, and conducted 12-lead concurrent electrocardiography during the surgeries.