The recent history of the para-hisian atrial tachycardia (PHAT) looks a lot like the older history of the atrioventricular (AV) nodal reentry tachycardia (AVNRT). The debate about precise anatomic boundaries of AV nodal reentry continues today again in the AVNRT, even 75 odd years after the first suspect that some mechanisms of supraventricular tachycardia could involve the region of the AV node. In this type of arrhythmia, the first target for the catheter ablative therapy was the fast pathway of the AV node: this approach showed a high success rate, but induction of AV block was found in more than one every five patients. After a few years, an approach was proposed from the slow pathway, that proved to be more effective and safer than the approach from the fast pathway. For some years, this new approach generated some debate in the electrophysiology (EP) community. Some authors even suggested to cross over from one technique to the other as long as AVNRT persisted. Nowadays, the approach from fast pathway is definitely abandoned and when we think of catheter ablation of AVNRT, we think only about ablation of the slow pathway.

PHAT are a group of atrial tachycardia (ATs) originating near the His-bundle (HB) region. Their prevalence is quite high in some casuistries, therefore it is important learning to recognize and to treat them. Nowadays, in the same manner of AVNRT, also for PHAT a debate is present for both the anatomic site of origin of this type of arrhythmia, both about the mechanism,^, both about the best catheter ablation approach.^– Some authors hypothesized the presence of a small re-entrant circuit adjacent to the tricuspid annulus; in contrast, other authors described PHAT as focal ATs arising from various location around the tricuspid or mitral annuli. PHAT are amenable to catheter ablation from multiple approaches including right inter-atrial septum, left inter-atrial septum by a transeptal puncture and non coronary sinus (NCS) of Valsalva of the aortic root by a transaortic approach via the femoral artery.

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