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.

Fig 89a.

Fig 89b. Admission ECG in 3o AVB. The temporary pacemaker has climbed toward the RV outflow tract (lead 2 positive) and operates on a hit and miss basis. The VEBs have the same morphology as in the two previous tracings.

Fig 90. 48 year old woman readmitted 48 hours after implantation of a permanent pacemaker.