Concealed Retrograde Conduction

Report:

Sinus rhythm 65/min

VEBs, mostly interpolated

Nonspecific ST/T changes

Comment:

For comparison, the last VEB blocks the ensuing P wave completely, producing a fully compensatory pause. Other VEBs merely prolong the subsequent PR interval, though concealed retrograde conduction – visible only by inference, by its effect on the next beat. Manifest retrograde conduction would have retrograde P waves instead. If there was no interpolation and all the VEBs caused AV block for the next P wave, the rhythm would be VEBs in trigeminy.

Below (Fig 150a) , the same VEBs are bigeminal. It’s easy to see that, were they to be interpolated, the interpolation would be in alternate cycles, again producing a form of trigeminy.

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