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