AVRT Reentry Circuits

So far, we have seen how an accessory pathway fulfills the three criteria for a reentry loop. These patients have an electrical circuit with at least two pathways, the two pathways have different underlying conduction properties, and there is an area of impulse slowing in one of the circuits (in the case of AVRT, the area of slowing is the AV node). By examining the anatomy of the two pathways, we see that the impulse from the atria can proceed in one of two ways: (1) The impulse can travel down the AV node and travel back up through the accessory pathway (Figure 26-3A), or (2) the impulse can travel down the accessory pathway and back up the AV node (Figure 26-3B). These two potential pathways will lead to the formation of the two electrocardiographic presentations of AVRT, orthodromic and antidromic AVRT.

Figure 26-3 Two possible reentry circuits formed in AVRT.

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