Echo Beats

Report:

Sinus rhythm (7 beats)

Ventricular tachycardia (4-beat run)

VEBs, couplet (two beats)

Reentry (echo) beats of ventricular origin (two beats)

Comment:

There are more QRS complexes of ventricular than supraventricular origin here - 8 vs. 7. Both episodes of ventricular ectopic activity are terminated by echo beats, marked by inverted P waves preceding them and QRS morphology identical to that of the sinus beats. If the sinus P waves are mapped forward through the ventricular ectopic rhythm, it will be easily seen that the echo P waves occur earlier than where a dissociated sinus P wave would be expected. It was a trick question57.

Two dissociated P waves are in fact obvious – one at the onset of the first broad complex and the other distorting the terminal portion of the first broad complex of the couplet.

One could not exclude junctional beats with retrograde conduction following the VEBs. But why should they follow them? Junctional premature beats are rare58. In general, regions with intrinsic automaticity, such as the AV junction or the sinus node, only infrequently produce premature beats59. God had escape beats in mind when He created them.