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].