Narrow VEBs & Trifascicular Block

Report:

Sinus rhythm 85/min

Second degree AV block, unspecified

VEBs in bigeminy

Right axis deviation +120o

Left posterior hemiblock

Right bundle branch block

Comment:

It’s best to observe the bigeminal VEBs in the rhythm strip: no two are the same. Not only that – they look more normal than the conducted sinus beats, the latter widened by the RBBB + LPHB. Are they fusion beats?

The nature of the previous 2:1 AV block is now difficult to define, beyond the general designation of second degree AV block. The VEBs themselves can induce advanced AV block67, but that variety is beyond standard classifications. Even then, is this block advanced (less than 50% conduction)? That depends on whether there is fusion or not. If there is, there is overall 3:2 conduction!

Below (Fig 404a) is a similar trace, but with uniform, also narrow, VEBs.

If you have any suggestions for or feedback on this report, please let us know.