METHODS
We conducted the differential diagnoses including CRT, His bundle pacing, and left bundle branch pacing. In order to obtain exact diagnosis, we arranged this patient a bedside chest X-ray. From the chest X-ray, we failed to find relevant pacing electrode placed in the field of left ventricle, His bundle and left bundle branch. The pacemaker on the right side is a 15-year-old single-chamber pacemaker, with its electrode lead located at the right ventricular apex(Figure 4a). The pacemaker on the left side is a one-week-old dual-chamber pacemaker with pacing electrodes situated in the right atrial appendage and the proximal septum (Figure 4a).
Moreover, three spike signals are observed during stable pacing periods, with fixed spikes occurring during in AV delay at 180 ms intervals, excluding other operation types such as CRT and His bundle pacing.