Ganglionated Plexi Ablation to Treat Patients with Refractory Neurally Mediated Syncope and Severe Vagal-Induced Bradycardia

DOI: 10.5935/abc.20190107 Neurally mediated syndrome (NMS) is the most common cause of and transient loss of consciousness and usually causes anxiety and concerns for patients and their families. Clinical investigation and explanations about benignity, in association to lifestyle modifications and teaching methods to abort the vagal reflex are the initial and effective approaches to manage the majority of patients.1-3 However, in some cases, the loss of consciousness occurs suddenly, without prodromal symptoms and the patient does not have the opportunity to prevent falls, which may lead to severe physical trauma. Specific medications have been proposed trying to control the symptoms and pacemaker implantation has been recommended in the refractory cases of cardioinhibitory reflexes.1-3 In 2005, Pachón et al.4 proposed using a catheter ablation technique to attenuate vagal activity on the sinus and AV nodes, through radiofrequency (RF) ablation of the sites related to vagal inputs to the atria. This procedure aimed to promote better quality of live for patients with refractory NMS and severe bradycardia, avoiding pacemaker implantation, especially in young individuals.4 Since that time, many reports have confirmed that atrial vagal modulation by catheter ablation is feasible in clinical settings, for patients with vagal induced marked and symptomatic bradycardia.5-20 However, those studies came from relatively few centers, such as case reports,5-13 or from non-randomized series involving a limited number of patients.14-20 Additionally, until now, there is no consensus about the criteria for patient selection, about how to perform an autonomic evaluation prior and post ablation, the best technique to be applied, the endpoints to conclude the procedure and what to expect during the outcome. These are the main reasons why vagal attenuation by catheter ablation has not been considered a possible treatment in the international guidelines of NMS management.1-3 Almost 50 years ago, experimental studies demonstrated that the sinus and atrioventricular nodes receive specific autonomic innervation, which can be surgically destroyed.21 However, current techniques to promote vagal denervation have been based on a more recent descriptions of atria innervation.22,23 It has been demonstrated that cardiac parasympathetic neurons get together with postganglionic sympathetic fibers and fat tissue (fat pads), in specific areas of the epicardium, adjacent to the posterior walls of left and right atria. Such ganglionated plexi (GP), working together, coordinate a sophisticated network that regulates cardiac functions, and more precisely the cardiac rhythm.24