Idioventricular Rhythm in Advanced AV Block

Report:

Sinus rhythm

Advanced (high-grade) second degree AV block

Left bundle branch block

Idioventricular escape rhythm

Right bundle branch block morphology

Ventricular fusion beats

Comment:

The escape rhythm originates from the distal left bundle branch, beyond the block: hence the RBBB morphology. Most escape rhythms in patients with BBB have the contralateral bundle branch block morphology. Fusion tends to normalise the QRS complexes, producing lean children of fat parents.

This patient was admitted with 2:1 AV block and LBBB, but the AV block became advanced, spontaneously, later on. It is not the presence of idioventricular escape beats that has caused it: there is still plenty of opportunity for 2:1 conduction, but it fails. On the other hand, the escape rhythm may well have increased the already advanced block. There is no saying what the conduction ratio would be without it.

169. 79 year old man with chronic IHD and COAD, on maintenance digoxin. He is having two for the price of one.