AIVR & Retrograde Conduction

Report:

Sinus arrhythmia

VEB (second complex in the top strip)

Atrial (?junctional) escape complex (9th in the top strip)

Accelerated idioventricular rhythm 86-89/min

Retrograde conduction

Fusion beats

Comment:

Typically, the retrograde 1:1 conduction is established in the second or third complex of each run of the AIVR. Prior to that, the preceding sinus impulse renders the retrograde pathway refractory. I have also seen, somewhere, a postulate that the establishment of retrograde conduction in this setting is due to the rate-dependent decrease in the refractoriness of the retrograde pathway. With the sinus P wave so close, however, it seems likely that the first mechanism wins the day (and the atria).

Atropine could be used in this setting to override the AIVR, but it is not easy to improve an asymptomatic patient. Presumably the AIVR is, in this instance, triggered by ischæmia.

The “subendocardial” infarction is in inverted comas because one cannot assign this diagnosis on the basis of the ECG any more. I like rhythm strips with writing on them, even (or especially) when incorrect. On the other hand, drawing asterisks or arrows over the ECG proper is barbaric and, worse, renders many of them unpublishable!