Fixed-Rate Pacemaker

Report:

Sinus rhythm 1

Left bundle branch block 3

Fixed-rate (asynchronous) ventricular pacemaker 39/min 6

Comment:

Large spikes denote a unipolar pacemaker, a feature not seen in temporary pacemakers. The slow rate would normally imply the battery depletion, but in this case the rate was slowed down by the ECG technicians in order to minimise competition and R-on-T pacing.

This is not a real asynchronous pacemaker (I have not seen one for many years); it’s a demand one with failure to sense. There is no failure to pace: all the “empty” spikes fall during the ventricular refractory period. It behaves exactly like a ventricular parasystole. If there was no pacing, one would not know for sure whether the pacemaker is atrial of ventricular.

The unit was replaced.

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