Background: Ablation of the cavotricuspid isthmus (CTI) using contiguous lesions guided by electroanatomical mapping on fluoroscopy assisted by the ablation index (AI) in typical atrial flutter (AFL) is a widely used procedure. Unipolar signal inversion during radiofrequency catheter ablation (RFCA) was found to be a predictive index of transmural lesion, as well as AI-guided strategy showed to be effective in CTI ablation while maintaining an inter-lesion-distance (ILD) ≤ 6mm. Both are related to the block of the CTI, however, it remains unclear how AI is related to the inversion of the negative component of the unipolar signal. The aim of our study is to evaluate the effectiveness of ablation based on unipolar recorded potential inversion and the corresponding AI values.
Methods: Thirty consecutive patients with AFL diagnosis were enrolled in our Centre to undergo CTI ablation. Patients were randomized 2:1 into the control arm and the experimental arm respectively. Contiguous lesions were performed using current AI standards until values of 500 were reached in the control group. In the experimental group, contiguous lesions were dispensed until inversion of the negative component of the unipolar signal was achieved, while simultaneously recording AI values. After CTI ablation, a 30-minute monitoring was performed to evaluate the efficacy and possible inducibility of AFL.
Results: A successful ablation procedure was performed in 30 patients. High-density mapping acquired on average 2766±1767 points vs. 2930±2177 (p=0.82), with a mean mapping time of 10.3±4.9 min vs 13.4±5.8 min (p=o.13). The procedural time between the two groups was comparable ( 77.9±27.6 vs 78.3 78.3±22.4 p 0.96). In both arms, the treatment effectively reduced the mean local potential in CTI (2.42±1.09 mV vs 2.71±1.26 mV p=0.51). Compared to the control group, unipolar signal inversion showed significantly lower ablation index values (500 vs 405±41.1 p < 0.0001).
Conclusions: The inversion of the negative component of the unipolar signal confirms to be an effective strategy in cavotricuspid isthmus ablation. Procedural success can be achieved at significantly lower corresponding ablation index values.