Ignored VEBs in Trigeminy

Report:

Sinus rhythm 1

VEBs, trigeminal 3

Atrial-sensing, ventricular-pacing electronic pacemaker 7

Comment:

This case is similar to No. 86, where the pacemaker leads cannot “recognise” the slowly rising ectopic R wave. Here, however, it follows the P waves throughout, through thick and thin; there is a spike even in the middle of the VEB complexes. This is the least culpable form of failure to sense.

The VEBs are all late-diastolic, an R-on-P phenomenon. They resemble WPW ‘A’ morphology due to the positive concordant precordial pattern and the P waves so close to the onset of slowly rising R wave. In fact, they could represent just that: the presumptive AV block may not be present in the anomalous pathway. This possibility is only mentioned for the sake of differential diagnosis; it remains an unlikely zebra.

The sensitivities adjusted, the VEBs were recognised by the pacemaker; the trigeminy persisted (Fig 89a).

Fig 89b is a tracing from her original admission, showing the same VEBs with junctional complexes and those of the temporary pacemaker. The sinus P waves are all dissociated and ignored by all three QRS varieties present.