Figure 3. Prolonged Recording of Lead II for 60 s
The above ECG characterized by two pacemakers indicates the following:
Firstly, the patient has a dual-chamber pacemaker operating normally in
DDD or VAT mode. Secondly, the pacemaker is in the stage of battery
depletion and has automatically switched to VOO mode. Additionally, the
pacing rate alternates between 30 and 60 bpm, with intermittent
ventricle capture observed. In summary, the ventricle capture is not
related to whether the pacing spikes are odd or even, thus eliminating
the possibility that the pacemaker is reserving power for a minute due
to battery depletion. Instead, ventricular capture is associated with
the supernormal phase of myocardial activity, which can respond to
subthreshold stimuli. The ventricular supernormal interval is determined
to range from 440 ms to 520 ms.
ECG, electrocardiogram; VOO, ventricular pacing, no sensing; DDD, dual
mode, dual sensing, dual pacing; VAT, ventricular pacing, atrial
sensing, tracking; bpm, beats per minute