Pacemaker Tachycardia with Spike Alternans
Report:
AV sequential pacemaker tachycardia 120/min 8
Pacemaker spike alternans 2
Comment:
The patient refused to stay in Casualty and went home. He returned several days later, when his pacemaker was “interrogated”. No malfunction was found in this DDDR unit. He was sent home (presumably with normal pulse rate).
This is not an endless loop tachycardia, since the atrial component of the unit appears to be pacing (the atrial wave is best seen in V1 as a shallow negative dip after the T wave). The atrial spikes should have then been suppressed by the putative retrograde P waves mediating the endless loop reentry. By the same token, this is not an atrial (or sinus) tachycardia 120/min sensed by the pacemaker: there would be no atrial spikes then either.
What is it, then? I do not know. When that happens, I tend to ascribe the event to some (unspecified) component malfunction, reinforcing my view with the pacemaker spike alternans41. The latter was only noticed because of the forced prolonged perusal of the trace, providing a “way out” for the frustrated interpreter. It involves both the atrial and the ventricular spikes but is much more noticeable in the former. Even then, this may well be just an artefact of digital signal processing42.
The large atrial spikes reflect their unipolar lead; the ventricular lead was bipolar.
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