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- ↵∗Heart Institute, São Paulo University, Eneas de Carvalho Aguiar 44, Pinheiros, São Paulo 05403-900, Brazil
We read with interest the article by Qin et al. (1) and the editorial comments by Zipes (2). It is, in fact, remarkable how vagal attenuation has become an important approach to deal with functional bradycardias. Since 2005, when the ablation of ganglionated plexi (GPs) was first described (3), this evolving technique has made significant contribution in the management of symptomatic atrioventricular block, cardioinhibitory syncope, and sinus node dysfunction, especially in the young population.
We agree that an anatomically guided mapping is more appropriate than the high-frequency stimulation strategy, in the sense that it enables the operator to perform a comprehensive ablation and avoid large scars. Yet, the observation that the ablation of the left GPs has almost no electrophysiological impact as compared with the ablation of the right anterior GP and the superior vena cava GP is in good agreement with previous data that set the interatrial septum as a main target in vagal denervation procedures (4). By taking these data into consideration, the authors could have obviated the left GP ablation, reducing the procedure time and limiting the radiofrequency (RF) lesion extension. Indeed, establishing the main targets and sparing noncritical areas are most relevant aspects of this therapy.
The endpoints chosen in this study also came to our attention, as the authors preferred using ablation of local atrial electrical activity and elimination of vagal response elicited by RF applications. Given that GPs are epicardial structures, it is reasonable to assume that the blunting of endocardial atrial electrogram does not necessarily mean effective vagal modification. Elimination of the RF evoked response seems to have low sensitivity as well. Even in extensive ablation procedures, such as atrial fibrillation ablation, vagal responses evoked by RF application are expected in no more than one-third of the patients. As Zipes (2) rightly pointed out, no measures of atrioventricular conduction, or other hard indicators of denervation have been presented. The most recent articles on GP ablation therapy (4,5) preferred using hard endpoints, such as heart rate elevation, HV interval shortening, a blunted response to atropine, and negative response to extracardiac vagal stimulation, instead of surrogate indicators that often result in widespread ablation.
In conclusion, this work, in agreement with previous important articles, has presented exciting clinical results and contributed valuable information. However, as appealing as cardiac denervation may be, it still lacks standardization. A multicenter, large scale, long-term follow-up study is of the essence to address important unanswered questions and confirm preliminary data about critical targets, proper endpoints, late impact, and reinnervation phenomena.
Please note: Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- 2018 American College of Cardiology Foundation
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