Is aberrancy same as functional bundle branch block ? Some electrophysiological entities are used too liberally without much meaning . The terms functional bundle branch block or rate dependant bundle branch block is actually used interchangably with aberrant conduction .It should be noted aberrant conduction can occur at extremes of heart rate .Even though tachycardia is expected to produce aberrant conduction extreme bradycardia as it can also make the cardiac conduction turbulent . Why aberrant conduction happens ? The his purkinje system expects some discipline and order from the SA node. Abnormal fluctuations in sinus heart rate keeps the downstream cardiac conduction system guessing and confused. The antegrade impulse penetrate to various levels and get struck with different refractory periods. In this scenario , if suddenly the basal heart rate swings further to different rates , the new incoming impulse finds , the preceding impulse has produced a functional block /barrier at the his purkinje level . (Note it should be called functional delay in conduction rather than a block as every impulse gets conducted ultimately with a widened qrs complex ).
- This type of conduction velocity mismatch between atrium and ventricle occurs in many of the SVTs and also in AF.
- It is found , aberrancy occur more commonly in the right bundle.
- It is usual for the aberrancy to disappear after the rate correction . Some times there could be a temporal delay . The conduction system might have gone for prolonged stunning . Some times this is referred to as ” memory blocks”
- Underlying heart disease, ischemia , degenerative heart disease may amplify this aberrancy or convert this transient aberrancy into a permanent block .
- It is also possible even a ventricular tacycardia might conduct with aberrancy , widening the already wide qrs tachycardia .(Refer this blog 🙂
Dr.S.Venkatesan MD 