Interpolated VEBs & Couplets

Report:

Sinus rhythm

VEBs, some interpolated, some (bottom strip) in couplets (pairs)

Comment:

In the top strip, the first VEB blocks the ensuing sinus P wave, creating a fully compensatory pause. The other two penetrate the AV junction retrogradely (concealed retrograde conduction) and make the sinus impulses conducted with a delay – 0.32”. The cycles containing the interpolated (intercalated) VEBs have no compensatory pauses, but are prolonged to the extent the subsequent PR interval is prolonged. The next sinus R-R intervals are correspondingly shortened.

The bottom strip is more complex. The VEB pairs occupy slightly longer cycles than the single VEBs and the first in each pair contains obvious atrial activity at its J-junction; so do the single VEBs. This atrial deflections can be either blocked sinus P waves or manifestly conducted retrograde ones; mapping them confirms the latter. The retrograde conduction changes from manifest to concealed for the second VEB in each pair, prolonging – albeit less than in the top strip – the subsequent PR interval. The sinus rate is considerably faster in the bottom strip.

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