Patterns of radiofrequency catheter ablation of left free‐wall accessory pathways: Implications for accessory pathway anatomy

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Abstract
Despite the abundance of literature on the electrophysiology of accessory pathways, clinical data on their anatomic properties remain infrequent. The small and discrete nature of lesions generated by radiofrequency (RF) energy may allow better characterization of accessory pathway anatomy in the intact heart. RF catheter ablation was performed on 40 left free‐wall accessory pathways in 39 consecutive patients with a unipolar endocardial approach. The patterns of accessory pathway ablation were identified. Spatial‐electrophysiologic information provided by the ablation catheter at individual sites of RF application and corresponding data from the coronary sinus catheter were correlated with the effects of RF energy on accessory pathway conduction. Of 39 accessory pathways permanently (n = 37) or transiently (n = 2) ablated, 24 had “simple” ablation, with abolition of conduction by one individual RF application. In 15 of 24 pathways that could be crossed by the coronary sinus catheter, the concordance in anatomic and electrophysiologic information between the site of earliest retrograde atrial activation and the effective ablation position (ventricular approach) suggested a perpendicular fiber course. Fifteen pathways had “complex” ablations; of these, eight had spatial‐electrophysiologic discordance between the atrial and ventricular insertions, suggesting an oblique fiber orientation. Seven pathways had modification or transient suppression of conduction, with or without subsequent abolition of conduction at identical or physically disparate (1 cm apart) sites; four pathways had sequential ablation of antegrade and retrograde conduction. These raised possibilities of broad fiber span and functional longitudinal dissociation of accessory pathway conduction. Accessory pathways with simple and complex ablations did not differ in clinical and electrophysiologic parameters. Complex ablations demanded more lengthy and difficult procedures. In conclusion, 38% of left free‐wall accessory pathways in this series had complex patterns of RF ablation. The results of this study raised interesting implications in regard to accessory pathway anatomy and provided information that might facilitate electrophysiologic guidance of RF accessory pathway ablation.