Shift in the earliest retrograde atrial activation site during the fast-slow form of atrioventricular nodal reentrant tachycardia after the radiofrequency modification of the atrioventricular node: is the atrium a necessary link?

Whether or not the perinodal atrium forms an upper link in the tachycardia circuit of the atypical form of AV nodal reentrant tachycardia (AVNRT) is controversial. We report a case with the fast-slow form of AVNRT in whom the earliest retrograde atrial activation site during the tachycardia changed from the right inferoseptum to the right superoseptum close to the His bundle without a change in the tachycardia cycle length following the radiofrequency energy applications to the earliest retrograde atrial activation site. It was speculated that a sub-atrial reentry with multiple atrial breakthroughs was the possible tachycardia mechanism in the present case.