Misleading Leads

Report:

Sinus rhythm 1

Left atrial abnormality (LAA) 1

LVH with ST/T changes (incomplete left bundle branch block) 2

Electronic pacemaker, probably atrium-sensing; failure to pace 5

Unusual (bamboo) spike morphology 1

Comment:

The distance between the onset of P wave and the pacing spike is only about 3mm – 0.12”; it is still a possible programmed value. The distance between the spike and the onset of the QRS complex is another 3mm; this segment is a flat line in all the leads. There is therefore no basis for belief that the QRS complexes may be paced, with a flat, isoelectric, initial segment.

The pacemaker artefact has a thickened segment in all the leads, like a river bamboo on its stick. There could be two leads firing simultaneously.

An hour later (below), the pacing spike moved spontaneously behind the QRS complex, still bearing a constant relationship to the native complexes, being approximately 4mm behind each QRS complex. This was unusual enough for an X-ray to be taken. It revealed both A and V leads in the right atrium!

Presumably the small cavity of the ventricle militated against a successful lead placement at the apex of the right ventricle and the lead was squeezed back into the right atrium. It is likely that both leads are firing – one tracking the P wave or the QRS complex, the other perhaps just “catching fire” from the tracking lead. Most likely both leads are tracking the QRS: the P wave is too far away.

Fig 75a.

Fig 76. 69 year old lady two days following CABGs.