Figure 1. Cabrera Sequence Recording

The above pacing ECG shows sequential capture of the atrium and ventricle, with dominant spikes at the beginning of the P wave and an aberrant QRS complex, maintaining a basic cycle of 1000 ms. The ECG reveals right atrial appendage pacing with a positive P wave in leads I, II, III, and aVF, a negative P wave in lead aVR, and a biphasic P wave in lead V1, with a PtfV1 of 0.05 mm/s. The ventricular electrode is positioned in the right ventricular outflow tract, indicated by a left bundle branch morphology in lead V1, a QS complex in leads I and aVL, and a tall R wave in leads II, III, and aVF. Additionally, 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. Upon encountering this ECG, a pacemaker interrogation was performed immediately.

ECG, electrocardiogram; AV, atrioventricular; CRT, cardiac resynchronization therapy