Failing Pacemaker

Report:

Sinus rhythm 1

Probable third degree AV block 1

AV dissociation 1 Ventricular escape beats 1

Primary T wave changes 1

Probable old anterior infarction 1

Pacemaker rhythm 72/min 1

Intermittent failure to pace 1

Probable lead displacement 2

Comment:

The bizarre frontal plane axis and the unexpected RBBB morphology of the paced beat in V1 indicate lead displacement, possibly a perforation. Failure to pace makes it even more likely. It could, however, be an epicardial pacemaker (it was not, historically).

The first escape beat is preceded by both a P wave and a pacing spike (best seen in V1), suggesting conduction of both, with ventricular fusion. The second escape beat, however, looks identical in the L2 rhythm strip at the bottom of the trace; its PR interval is longer and there is no spike artefact at the QRS onset. This means that the first beat is of the same (ectopic ventricular) provenance as the second.

In V6, the T wave of the escape beat is unexpectedly concordant with its QS complex, denoting a myocardial pathology supported by QR complexes in V4-5 above it. Even in ventricular ectopic beats, this indicates a previous infarction37.

Fig 61. Sprightly 91 year old lady with a 16 year old VVI pacemaker implanted following episodes of atrial fibrillation (and its therapy). This trace was taken during one of her visits to Casualty for stabilisation of diabetes mellitus.