Fig. 1

Electrocardiogram, hemodynamic monitoring and radiographs. A1: ECG showed ventricular tachycardia, corresponding to hemodynamic instability before temporary His bundle pacing. The paper speed was 25 mm/s; A2: ECG showed sinus arrest with ventricular escape rhythm and central venous pressure of 12 mmHg before operation. The paper speed was 25 mm/s; A3: ECG showed atrial-ventricular sequential pacing in DDD pacing mode with hemodynamics improved postoperatively. The paper speed was 25 mm/s; B1: Fluoroscopic RAO 30°and LAO 40° projection showed relative position of the pacing lead in the low right atrium (red thick arrow) and His bundle (white thick arrow) position respectively; B2: Intra-cardiac electrogram showed big His potential (blue arrow) with HV interval of 59 ms and selective HBP at 1 V/0.5 ms. The paper speed was 100 mm/s; B3: Intra-cardiac electrogram recorded on pacemaker programmer showed atrial pacing at 50 bpm could realize 1:1 atrial to ventricle conduction, while atrial pacing at 60 bpm resulted Wenckebach phenomenon of atrioventricular conduction. The paper speed was 12.5 mm/s; B4: Chest radiographs showed pulmonary congestion and cardiothoracic ratio increased to 0.63 before temporary conduction system pacing (left) while reduced to 0.59 after device implantation (right), the red arrow showed that the temporary pacemaker was fixed on the skin