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Can AV Node Ablation Help Save AV Conduction?

One of the most feared complications for patients undergoing ablation of supraventricular arrhythmias is need for permanent pacing. Injury to the cardiac conduction system resulting in atrioventricular (AV) block occurs in about 1% of patients with AV nodal reentrant tachycardia (AVNRT),1,2 as well as a small percentage of patients with septal AV accessory pathways or paraHisian atrial tachycardia. Somewhat conflicting predictors of AV block with AVNRT ablation have been reported by several small observational retrospective studies. In this issue of PACE, Gondo et al. take a novel approach to identification of predictors of AV block.3 They report on 10 successful AV node ablation procedures performed for drug refractory supraventricular tachyarrhythmia. Radio frequency (RF) energy was applied in a stepwise approach from the posterior region of the septal annulus of the tricuspid valve to the His bundle potential (HBP) recording site. They recorded anatomical and electrophysiologic characteristics of each ablation site—atrial/ventricle potential amplitude ratio (A/V ratio), fluoroscopic distance between the ablation site and the HBP recording site (H–ABL distance) and the interval from the atrial signal on the His catheter to that on the ablation catheter (H–ABL interval)—as well as response to ablation, in terms of the presence and rate of ensuing junctional ectopy (JE). Creation of AV block can be difficult. Two of their original 12 patients were excluded from the study because of lack of success. Even when a HBP was present, fewer than half of all RF applications resulted in any degree of even transient AV block. Lesions close to the His catheter (H–ABL distance of <12–15 mm) and with a tight HABL interval (<10 milliseconds) produced AV block only about a half and a third of the time, respectively.