Post-Ectopic SA Depression Mime of SA Wenckebach

Report:

Sinus rhythm 87/min

SVEBs, blocked

First degree AV block

Right bundle branch block

Comment:

Acceleration before pauses is the hallmark of SA Wenckebach exit block. This would be a good example if the pauses were not generated by premature blocked P’ waves, easily seen notching the ST segment just before the T wave in each long cycle.

The PR interval in each long cycle is slightly shorted than the others, but there is no progressive prolongation – this is not an AV Wenckebach, either. It is permissible for the first PR interval in a group to be shorter than others – there’s more time for AV nodal recovery. This is always more apparent with pre-existing 1o AV block, as in this case.

The AV block was present preoperatively and got worse immediately after the MVR four days previously (Fig 153a below).

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