Paradigm Shift for Catheter Ablation of Atypical Atrioventricular Nodal Re-Entrant Tachycardia

In current practice, the ablation target of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway region.The purposes of this study were to map the site of earliest retrograde atrial activation using electroanatomic three-dimensional mapping during atypical AVNRT and to evaluate successful ablation sites.A total of 42 patients with a total of 49 AVNRTs (slow/fast: 30; fast/slow: 15; slow/slow: 4) underwent electrophysiological study and ablation. Among them there were 14 patients (10 women; 60 ± 19 years of age) in whom 19 atypical AVNRT (fast/slow: 15; slow/slow: 4) were induced.The intracardiac electrocardiograms or three-dimensional mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension [LIE]), 3 solely in the right postero-septal tricuspid annulus (TA; right inferior extension [RIE]), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14 ± 6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o'clock in the left anterior oblique projection). Ablation targeting these exits or conventional slow pathway succeeded in long-term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications.Catheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.