DP+1: Another simple endpoint for atrial flutter ablation

DP+1. Background: When double potentials (DP) on the line of block are difficult to see, we propose another simple method to verify complete bidirectional block (CBDB) at the end of an atrial flutter ablation. We measured the interval between the electrograms immediately on either side of the line of block on a multipole catheter spanning the isthmus. We called this interval "DP+1" because it is one pair of electrodes away from the DP on the line of block. Methods: Fifty consecutive patients (age 62 ± 13 years, LVEF 54 ± 11%, mean cycle length 241 ± 34 ms) underwent an atrial flutter ablation using a duodecapolar catheter with 2-10 mm spacing with the distal tip inserted into the mid-coronary sinus and the rest of the poles spanning the isthmus and the low lateral right atrium. Radiofrequency ablation was performed using a 10-mm tip electrode (EP Technologies). The ablation endpoint was the creation of a craniocaudal activation pattern of the opposite wall to the pacing site (septal and lateral of the line of block). Results: The ablation endpoint was achieved in 48 of 50 (96%) patients with 8 ± 2 RF applications. Adequate DP were found in only 22 of 50 patients (44%), but the DP+1 interval was measurable in all patients. When no block was present, the DP+1 interval was 81 ± 10 ms, and 160 ± 18 ms when complete bidirectional block was present (P < 0.001). A DP+1 interval of >140 ms had 100% specificity, 96% sensitivity, 100% positive predictive value for verifying complete bidirectional block. After a follow-up of 528 ± 253 days, there were no recurrences of AFL, but there were four recurrences of AF (8%). Conclusion: When DP cannot be seen, another simple method for verifying CBDB in ablation of typical atrial flutter is a DP+1 interval > 140 ms.