Impact of tag index and local electrogram for successful first-pass cavotricuspid isthmus ablation.

Background: The optimal ablation index (AI) value for cavotricuspid isthmus (CTI) ablation is unknow.

Objective: This study investigated the optimal AI value and whether preassessment of local electrogram voltage of CTI could predict first-pass success of ablation.

Methods: Voltage maps of CTI were created before ablation. In the preliminary group, the procedure was performed in 50 patients targeting an AI ≥450 on the anterior side (two-thirds segment of CTI) and AI ≥400 on the posterior side (one-third segment of CTI). The modified group also included 50 patients, but the target AI for the anterior side was modified to ≥500.

Results: In the modified group, the first-pass rate of success was higher (88% vs 62%; .01) than in the preliminary group, and there were no differences in the average bipolar and unipolar voltages at the CTI line. Multivariate logistic regression analysis revealed that ablation with an AI ≥500 on the anterior side was the only independent predictor (odds ratio 4.17; 95% confidence interval 1.44-12.05; .01). The bipolar and unipolar voltages were higher at sites without conduction block than at sites with conduction block (both .01). The cutoff values for predicting conduction gap were ≥1.94 mV and ≥2.33 mV with areas under the curve of 0.655 and 0.679, respectively.

Conclusions: CTI ablation with a target AI >500 on the anterior side was shown to be more effective than an AI >450, and local voltage at a conduction gap was higher than without a conduction gap.