Is This Ventricular Tachycardia?

I reported this Holter this week.

The report said ventricular tachycardia (red highlight). What do you think?

Most of you will say atrial fibrillation with a rapid ventricular response and intermittent aberrant ventricular conduction and you will be correct.

We covered the topic a couple of weeks ago (Fun with ECGs 16).

There is, however, a major difference from the usual aberration! Can you pick it?

Firstly, let us briefly review aberration again:

• Aberrant conduction results from intermittent uneven physiologic refractoriness in the ventricular conducting system from an early supraventricular beat.  
• There is QRS widening, consequent to a delay or block in one of the bundle branches or a more peripheral branch.

A feature of the right bundle branch block are“rabbit’s” ears; rsR’ in V1:

This was coined by the great teacher of ECGs; Henry “Barny” Marriott in St Petersburg, Florida. He is in the top hat with his ever-devoted fellow on the left.

Why then is the aberration in the first illustration different?

Firstly, there is one bundle branch block (yellow highlight):

Then another (red highlight):

Or both together (red and yellow highlight):

Thus there is aberration involving both bundle branches.

Although right bundle branch block is usually associated with aberration, left bundle branch block can also occur, even in the same patient. This was determined in the early days of electrophysiology studies in the US at a time when half of the published manuscripts in all the cardiology journals were ECG/EP related.

The finding of both bundle branch blocks in the same patient is probably rare, but may not be so, if you look for it.

A final point often asked is whether you can tell the bundle branch block site with a Holter monitor. We always say no, but there are clues.

There are two ways of attaching leads for Holter monitoring with both having some advantages:

On the right is the way CardioScan recommends.

The middle lead is V1 and should be negative or at least isoelectric.

Knowing that we can return to our case study and the yellow highlight is a right bundle branch block with rabbit’s ears.

Once again it is all in the timing.

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