AIVR & Quadrigeminal VEBs

Report:

Accelerated idioventricular rhythm 90/min (AIVR)

Retrograde VA conduction

Wenckebach phenomenon

VEBs in quadrigeminy

Fully compensatory pauses (in the AIVR)

Comment:

The first impression is that of dissociated sinus rhythm due to variable P-QRS intervals. The early rS complexes, with long PR intervals, would then represent sinus captures.

This is not so. The P waves are obviously related to the preceding QR complexes of the AIVR, with increasing R-P intervals until the sequence is interrupted by a broad rS complex. This is consistent with retrograde Wenckebach conduction through the AV node. If the P waves were dissociated sinus P waves, one would expect to find them 'marching through' the pauses created by the broad QR beats. They would fall on the ST segment of the QR beats, where it would be easy to see them. They are missing there because the AIVR complexes from which they originate are missing.

The rS complexes have a primary R wave 0.04" and a slurred descent - hallmarks of ectopic right ventricular origin. Below is a strip of the patient's sinus rhythm, with a VEB and another run of AIVR. Note how the retrograde conduction improves (shortens) for the last AIVR beat, due to a prolonged preceding cycle.