The purpose of this study was to evaluate the predictive strength using the criterion of trans-isthmus conduction (TIC) time of≥130 ms post ablation of typical atrial flutter (AFL) for complete bidirectional conduction block, which was confirmed with high-density mapping (HDM) of right atrium.

This was a prospective, single-arm and open multicenter study. The patients, aged (56.58±11.73) years, 31 males, referring for cavotricuspid isthmus (CTI) -dependent AFL ablation were consecutively enrolled between December, 2014 and July, 2016. TIC intervals between the coronary sinus ostium (CSO) and low lateral right atrium (LRA) were recorded after ablation. Complete CTI block was determined by HDM of the right atrial activation. The sensitivity, specificity, positive and negative predictive values were calculated for the criterion of TIC time of≥130 ms.

After the initial CTI ablation, conduction gaps in the ablation line were found in 10 of the 23 patients with TIC time≥130 ms and 14 of the 16 patients with TIC time <130 ms. The criterion of using bidirectional TIC time≥130 ms predicted complete CTI block with 86.67% sensitivity and 58.33% specificity. The positive and negative predictive values were 56.52% and 87.5%, respectively. Of the 24 cases with conduction gaps post ablation, 14 were found on Eustachian valve (EV) , 4 on the tricuspid valve end of the CTI, 1 on the both end and 5 were not available.

The study suggests that TIC time of≥130 ms should not be used as a criterion for complete bidirectional conduction block of CTI after liner ablation and that HDM can be a more reliable criterion. The EV end of the CTI is the most common site for conduction gaps.

Atrial flutter; Catheter ablation; Cavotricuspid isthmus; High-density mapping