Initiation of AV node reentry (AVNRT)

on 7.12.08 with 0 comments

  • about 40% of the population has two pathways in AV node—fast pathway F and slow pathway S

  • these two pathways have all the requirements for reentry

    • fast pathway has fast conduction but very slow repolarization (criterion 1)

    • slow pathway has slow conduction (criterion 3)

    • unidirectional conduction block (criterion 2)

    • SA node fires. AP goes through fast pathway straight to ventricles. it is blocked in the slow pathway because the AP propagates so slowly through S

    • F then takes a long time to repolarize (criterion 1); the next SA node beat, which is early, can’t go down F because F is still repolarizing. so, the early beat goes down S

    • by the time F has finished repolarizing, the early beat has passed through S and now “wraps around,” retrograde, to activate F from “below”

Category: Pathology Notes



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