Reappraisal and new observations on atrial tachycardia ablated from the non-coronary aortic sinus of Valsalva

We read with great interest the work published by Bohora et al.1 and we agree that in the vast majority of cases it is possible to eliminate this subgroup of atrial tachycardias (ATs) with early activation close to the His-bundle from the aortic root and in particular from the non-coronary aortic cusp (NCC). This has an anatomical explanation: the NCC in fact delineates the superior aspect of the paraseptal region, lying on the epicardial tissue between the right and left septum, and thus provides access to this area. Bohora et al. reported a 100% success in eliminating these ATs by radiofrequency (RF) energy application in the NCC only. However, as reported in two recent large series,2,3 although ablation from the aortic root, frequently chosen as the first site, is often successful in eliminating the AT, in some cases mapping and ablating the left septum is needed. In addition, as described by Wong et al.,4 when the left septum was the initial strategy to treat these ATs, this approach was also successful in most patients without the need of mapping the aortic root. We agree with the analysis done by Markowitz5, and when treating these ATs, we should keep in mind the complex anatomy of the para-Hisian region and consider that there are three potential locations to achieve success from: the right septum, the left septum, and the NCC. In contrast to Bohora et al., we and others3 described very similar local activation time in these three structures. In our opinion, when dealing with this subgroup of ATs we are in front of a puzzle, where the main pieces, the right and left atrial septum and the aortic root, all play an important role. Therefore, we believe that these ATs would be better defined as ‘para-Hisian’ ATs, giving better insight into the substrate and thus, the appropriate ablation strategy. This term would fit better than the one describing the ATs as successfully eliminated from the NCC which does not represent a pathophysiological entity but just one of the three possible approaches to achieve success. Often, para-Hisian ATs require mapping from several structures to exactly determine early local activation time, since the substrate is delineated by epicardial tissue in the para-Hisian region. Finally, para-Hisian ATs still represent a challenge and source of some debate in the electrophysiology community. Although there is agreement on some aspects, like the ‘nodal-like’ response to adenosine, and the narrow P-wave during AT, there is a lot of disagreement about the characteristic P-wave morphology during AT. We observed a peculiar narrow biphasic (−/+) or triphasic (+/−/+) P-wave in the inferior and precordial leads (especially V4–V6) in most of the cases2. However, this observation was not reproduced in the recent series. Therefore, we believe that an effort to better characterize the P-wave during these ATs would be of great advantage.