Efficacy of bundle ablation for cavotricuspid isthmus-dependent atrial flutter: Combination of the maximum voltage-guided ablation technique and high-density electro-anatomical mapping

Introduction Pathological studies have demonstrated that the cavotricuspid isthmus (CTI) is often composed of discrete muscle bundles, which are thought to be represented electrically as high-amplitude electrograms. Based on this observation, we visualized the bundles using an electro-anatomical mapping system (EAMS) and investigate the efficacy of bundle ablation which is an ablation method for selectively targeting high-voltage sites obtained by high-density electro-anatomical mapping along the CTI. Methods Sixty patients with atrial flutter were randomly assigned to cavotricuspid isthmus ablation using a conventional anatomical approach (Group 1) or bundle ablation approach (Group 2). In Group 2, CTI was mapped in detail with EAMS, and we visualized the bundles that were 1.5 mV or more on a bipolar voltage map. Radiofrequency (RF) ablation was delivered sequentially from the maximum voltage site at the shortest distance of the bundle until bidirectional block was achieved. Results Bidirectional block was achieved in all patients. Mean ablation times (Group 1, 1,392±960 s; Group 2, 638±342 s, p<0.01), the mean number of RF applications (Group 1, 31.7±23.6; Group 2, 13.0±7.0, p<0.01), and fluoroscopy times (Group 1, 50.4±28.3 min; Group 2, 42.3±21.3 min, p< 0.01) were significantly shorter in Group 2 than those in Group 1. Conclusion Bundle ablation at CTI is highly effective for achieving a bidirectional block requiring shorter ablation times, shorter fluoroscopy times, and fewer RF applications.