Aberrant Ventricular Conduction

The CardioScan technicians recently reported this ectopic on a Holter monitor as a trial with aberrant ventricular conduction.

The responsible physician disagreed and insisted the ectopics be called ventricular.

What do you think and how do we differentiate between them?

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As this was a Holter monitor, look at the timing of the other ectopics.

The later the ectopic, the more it looked like the sinus QRS.

Also a P wave emerged (4).

Clearly the technician was correct in calling them atrial ectopics with aberrant ventricular conduction, rather than ventricular ectopics.

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What is aberration?

Aberrant conduction results from intermittent uneven physiologic refractoriness in the ventricular conducting system from an early supraventricular beat with the right bundle branch action potential being usually longer than the left bundle branch.

There is QRS widening, consequent to a delay or block in one of the bundle branches or a more peripheral branch. Because the right action potential is usually longer the appearance is usually a right bundle branch configuration.

Remember, unless you know the lead placement for the Holter monitor, you cannot tell which bundle branch block it is.

Let us look at the action potentials:

When attempting to determine the site of origin of an ectopic look for:

Aberration was first described by Gouaux and Ashman in 1947 in patients with atrial fibrillation. They also described a long cycle/short cycle phenomenon. With along cycle, the relative refractory period lengthens allowing a zone of aberrancy to emerge.

Marriott (my mentor), described the right bundle branch block “rabbit’s ears”appearance (rsR’ in V1), which is so commonly seen with the right ear higher than the left.

Why bother trying to differentiate between atrial and ventricular complexes?

When first described, it was important with atrial fibrillation as aberration denoted too fast a rhythm requiring more digoxin, whereas ventricular ectopy suggested digitalis toxicity.

Today it is more an exercise in recognising rhythm disturbances as seen in the next two illustrations.

In both of these cases, the rhythm was described as runs of ventricular tachycardia in the presence of atrial fibrillation with a rapid ventricular response.

Its all in the timing.

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