PseudoWenckebach in Ventricular Pacemaker

Report:

Sinus tachycardia 122/min. 1

Möbitz 1 AV block, 5:4 and 4:3 conduction. 2

Atrial-sensing ventricular pacemaker (probably a DDD pacemaker). 3

Pseudo-Wenckebach. 4

Comment:

The ventricular complexes are all paced and all identical, indicating no atrial contribution (i.e., fusion) at any of the conducted PR intervals. They show the expected LBBB morphology with LAD (result of right ventricular apical pacing). Like the right ventricular VEBs - but unlike the true LBBB - they show a slurred descent in lead V1. They are also, at the rate 122/min, sensing the sinus P waves.

Art imitates nature. The mechanism of ventricular pacing (and failure to pace) replicating “natural” Wenckebach, with P wave as the proximal and paced QRS as the distal component, involves an independent electronic function which limits the upper ventricular rate by progressive increments in AV interval until a P wave is not sensed. This is known as pseudoWenckebach17.

A 1:1 conduction at the rate of 110/min is shown below (Fig 23a).

As often happens, no cause was found for the patient’s pain and he was sent home. One should look at the PR segments for evidence of pericarditis, but this trace is too wobbly for that.

Fig 23a.

Fig 24. Two weeks post-implantation of a permanent pacemaker, this patient’s ECG was neither here nor there.