Proportion of ORTs Relying on Aberrancy
From our 95 cases of ORT with aberrancy, only 3 showed solid evidence proving BBB was indispensable. The others included ORTs with pre-existing BBB, concomitant wide and narrow QRS, and those only showing wide QRS. In the latter situation, sensed extrastimuli with different prematurity have been attempted in straightforward cases but failed to reactivate the blocked bundle. Therefore, it remains unknown whether those cases were relying on aberration or not. Additionally, the conduction velocity and refractory period of AV node and AP can be altered by medications and autonomic nerve activity, which may influence the dependence of aberrancy during EP study.