Radiofrequency ablation (RFA) of cardiac parasympathetic ganglionated plexi (GPs), termed cardioneural ablation (CNA), has been shown to successfully treat vasovagal syncope (VVS). Sinus (SN) and atrioventricular (AVN) nodes are innervated by distinct GPs in the epicardial fat pads of both atria. We present a case of CNA of SN-specific GPs for VVS eliminating sinus arrest, but recurrent syncope with AV block.
A 36 year-old man with frequent VVS with sinus arrest documented on implantable loop recorder (ILR) was referred for CNA. Intervals at baseline: PR 208 ms, AH 137 ms, HV 50 ms. Bi-atrial mapping was followed by RFA at the anatomic sites of the Marshall Tract, left superior, right superior, and Aortic-SVC GPs. Vagal responses (sinus arrest and AV block) were seen during ablation of the left-sided GPs while his sinus rate increase observed during ablation of the right sided GPs. The posteromedial GP and right inferior GP were not ablated. Follow up ILR recordings showed reduced heart rate variability and increased sinus rates. Five months post-ablation another syncopal event occurred. ILR revealed 11 seconds of ventricular asystole due to complete AV block at unchanged sinus rate. Repeat CNA with RFA of the right inferior and posteromedial GPs resulted in decrease in PR from 213 to 176ms, AVN Wenckebach cycle length from 500 ms to 450 ms, AVN effective refractory period from 600/450 ms to 600/370 ms, and progressive decrease in AH interval with decreasing pacing cycle length (700 ms: from 101-> 93 ms , 600 ms: 142-> 120ms, 550 ms: 163 ->129 ms, and 500 ms: 193 -> 142 ms) with no further change after atropine challenge. The patient has had no further syncopal events.
CNA can reduce VVS burden. Isolated ablation of the GPs providing SN innervation does not prevent VVS caused by AV block due to the distinct GP innervation of the AV node. Patients with VVS due to a SN cardioinhibitory response should be considered for CNA of AVN-innervating GPs since vagal AVN response can be initially masked by SN arrest. Changes in AH interval response curves at different paced cycle lengths provide a clearer endpoint for AVN modification than comparing intervals during sinus rhythm before and after ablation.