Advanced 2o AV Block

Report:

Sinus rhythm

Progressive first degree AV block (top)

VEBs

Advanced second degree AV block

Comment:

The 14 second pause follows the VEB, but the ground had been set even before the first VEB: a single blocked P wave is seen at the end of the top strip and the sinus cycle lengthening with increasing PR interval also preceded the VEB.

Throughout the pause, there is no sinus acceleration, expected on hæmodynamic grounds; the resumed conduction at the end of the bottom strip still includes relative bradycardia and first degree AV block. The second VEB appears to be preceded by a P’ wave, but this is merely an artefact, since the real P waves march unconcernedly throughout. Its morphology, too, would strongly suggest supraventricular origin in lead V1 – but this is standard lead 2.

Note that both VEBs are followed by 2o AV block, like in Case 132.

The patient also had episodes of sinus arrest, with junctional bigeminy (Fig 138a below). The appearances (including second degree AV block) are consistent with sick sinus syndrome.