The re-entry circuit is formed either by the functionally discrete pathways within the AV node and the perinodal region, as discussed on pages 7.1.26 and 7.1.27; or by the pathways created by an AV nodal bypass tract. The P waves that occur during the tachycardia may be difficult to identify because they frequently fall within the QRS complex or the early portion of the ST segment.
These arrhythmias are commonly referred to as paroxysmal supraventricular tachycardias (PSVT) and/or as “reciprocating tachycardias.” They are further defined as an AV nodal re-entrant tachycardia (AVNRT) when the re-entry circuit is within the AV node and perinodal tissues, or as an AV re-entrant tachycardia (AVRT), when one pathway of the circuit is an AV nodal bypass tract.