EP Findings Supporting the Need for Aberrancy
When BBB was improved, advanced wavefront encountered refractory period
of AP or normal AV conduction system via different mechanism which
validated the need for aberration (Central illustration).
In case 1, a His-refractory PVC advanced the subsequent A and His
through the AP. Meanwhile, it peeled back the refractoriness of the left
bundle by “pre-exciting” it from retrograde direction, which narrowed
the next QRS. The 2 effects above advanced the ventricular signal at
anterolateral mitral annulus (VCS1-2) by 60msec, which
was in the refractory period of AP. Case 2 had similar mechanism as case
1, while resolution of block was spontaneous. The local V and following
A on the left side were advanced in this beat which made the wavefront
reaching the atrioventricular junction (could be AV node or His-Purkinje
system) during refractoriness.
In case 3, stable tachycardia could only be induced when RBBB was
created together with slow pathway conduction. With isoproterenol given,
slow pathway was replaced by fast pathway to participate in reentry,
followed by improvement of aberration resulting in premature
depolarization of AP, which afterwards advanced the input into AV
junction and again blocked the fast pathway. It suggested both infra-His
block and slow pathway conduction contributed to maintaining reentrant
activation. Interestingly, the narrow QRS tachycardia had a longer TCL
than the wide complex owing to marked increase in AV interval,
demonstrating a reversed finding to the “Coumel’s
law”[5].