Atrial ectopy originating from the posteroinferior atrium during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia

Atrial ectopy sometimes appears during RF ablation of the slow pathway in p atients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examin e these issues, we analyzed 67 consecutive patients with AVNRT (60 with slo w-fast AVNRT and 7 with fast-slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patient s. During successful RF ablation, junctional ectopy with the activation seq uence showing H-A-V at the His-bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A-H-V at the His-bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 p atients) or without junctional ectopy 15 patients). Before RF ablation, ret rograde slow pathway conduction induced during ventricular burst and/or ext rastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.002). Successful ablation site in group A was distributed between the His-bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coron ary sinus ostium. In group B, atrial ectopy also appeared in 21% of the uns uccessful RF ablations. In conclusion, atrial ectopy is relatively common d uring slow pathway ablation and observed in 8% of RF applications overall a nd 21% of RF applications that successfully eliminated inducible AVNRT. A t rial ectopy appears to be closely related to successful slow pathway ablati on among patients with manifest retrograde slow pathway function.