Inferior Infarction: Blocks and Arrhythmias

Report:

Sinus tachycardia 122/min

Second degree AV block, unspecified

Junctional escape beats and rhythm 46/min

Non-phasic aberrant conduction

Acute inferior infarction

Comment:

It is said that the presence of 2o AV block in inferior infarction denotes additional, independent disease of the LAD artery57. This was certainly the case here: the left circumflex (infarct-related) artery was completely occluded, with 80% lesion in the LAD artery; the RCA was small, non-dominant, and had only a 30% narrowing. This anatomy was subsequently deemed inoperable.

The AV block is reported as unspecified only because there are no consecutive conducted P waves; the three conducted (with 1o AV block) sinus beats could be described as capture beats in AV dissociation with interference. They are the interference. In this setting, however, the block is almost certainly AV nodal (rather than ventricular) and would show Wenckebach periodicity at another time. It did that, in the tracing below (Fig 80a), with bigeminy due to 3:2 conduction.

The junctional beats are slightly different (short and stubby in the rhythm strip, terminating long cycles), presumably due to a different activation front from a junctional focus. This constitutes what Schamroth called non-phasic aberrant conduction – non-phasic because it des not depend on long-short cycle sequences.

In the next 8 pages, included here for teaching purposes, the patient shows typical blocks and rhythms of inferior infarction: 3o AV block, 2:1 AV block, 1o AV block, AF and flutter with 3o AV block and conducted, and eventual sinus rhythm with only borderline 1o block.