Figure 2. Cabrera Sequence Recording
The above ECG characterized by two pacemakers indicates the following: Firstly, the patient has a dual-chamber pacemaker operating in DDD or VAT mode, with both sensing and pacing functions being normal. Secondly, the pacemaker is in the stage of battery depletion and has automatically switched to VOO mode. Additionally, the pacing rate alternates between 30 bpm and 60 bpm, with a few unipolar pacing spikes successfully capturing the ventricle (as seen in the second and last aberrant QRS complexes). Lastly, the QS complexes in the inferior and precordial leads, as well as the R wave in leads I and aVL, align with the pacing characteristics of the right ventricular apex. Meanwhile, a chest X-ray confirms the anatomical locations of the electrodes. This ECG demonstrates the characteristics of both pacemakers, leading us to recommend extracting the old pacemaker generator (Figure 4b).
ECG, electrocardiogram; VOO, ventricular pacing, no sensing; DDD, dual mode, dual sensing, dual pacing; VAT, ventricular pacing, atrial sensing, tracking; bpm, beats per minute