Elimination of cavotricuspid isthmus conduction by a single ablation lesion: observations from a maximum voltage-guided ablation technique.

AIMS: The architecture of the cavotricuspid isthmus has been shown to be highly variable made of a large number of interspersed bundles in the majority. Targeting high-amplitude signals has resulted in short-ablation times, likely due to the selective ablation of such bundles. We report a series of cases where a single site ablation resulted in bidirectional block, supporting the hypothesis that conduction can occur over a discrete portion of the isthmus. METHODS AND
RESULTS: Sixty consecutive patients underwent ablation for isthmus-dependent atrial flutter using voltage-guided approach between September 2005 and June 2006. We found in five patients (8.3%) (four male, mean age 58.1 +/- 11.4 years), in whom bidirectional block was achieved by ablation at a single site. The isthmus was mapped at the 6 o'clock LAO position, and bipolar amplitude was measured during pull-back to find the site of largest atrial voltage. The atrial and ventricular electrogram (EGM) measured 2.00 +/- 1.6 and 0.2 +/- 0.1 mV, respectively, at the successful site, resulting in the mean atrium/ventricle ratio of 9.1 +/- 4.1. The total radiofrequency time was 83.8 +/- 25.3 s, and the procedure time was 68.6 +/- 10.4 min, including 30 min waiting time after the procedure. Flutter has not recurred over 5.7 +/- 4.0 months follow-up.
CONCLUSION: Targeting the largest atrial EGM in the isthmus can produce bidirectional block with a single site ablation. This supports the hypothesis that trans-isthmus conduction can occur over a discrete part of the isthmus, likely due to the underlying bundle architecture.