Is it truly atrial tachycardia?

We read the article by Okumura et al. [1] with great interest. The authors reported an ablation strategy applying manifest entrainment to treat adenosine triphosphate (ATP)-sensitive atrial tachycardia (AT) originating from the perinodal region. However, we have some concerns regarding the electrophysiological diagnosis of the tachycardia. The exclusion of atrioventricular nodal reentrant tachycardia (AVNRT) is essentially a prerequisite to diagnose AT. The authors excluded AVNRT based on the findings of atrioventricular dissociation during the ventricular pacing of tachycardia and a V–A–A–V activation sequence on ventricular induction of tachycardia. We do not believe that these findings exclude the diagnosis of AVNRT. Recently, we reported a novel form of fast–slow (F/S) AVNRT incorporating a “superior” slow pathway located at the top of the Koch's triangle (sup-F/S-AVNRT) [2] with electrophysiological characteristics that included a long RP interval, the earliest site of atrial activation near the His-bundle, ATP sensitivity, and the successful ablation site in the perinodal region, which were strikingly similar to those of the tachycardia in Okumura's study. Importantly, in some cases of sup-F/SAVNRT, the finding was caused by ventriculoatrial block in the lower common pathway below the atrioventricular nodal reentry circuit and was satisfied because of double atrial responses using fast and superior slow pathways. Therefore, we wonder if the