Aberrant conduction occurs when the length of the cardiac cycle is changed without a compensatory change in the length of the refractory period. This is explained by the changes of the refractoriness in the His-Purkinje system related to changes in the RR interval.

What is meant by SVT with Aberrancy?

Any tachycardic rhythm with a left or right bundle branch block that is NOT ventricular tachycardia is considered “supraventricular tachycardia with aberrancy”.

Why do aberrant PACS occur?

Aberrant conduction occurs simply because the right and left bundle branches have different lengths of refractory periods. In Figure 2, the shaded area is the refractory period of the left and right bundle branches. As can be seen, one bundle branch, usually the right, has a longer refractory period than the other.