Background Ethanol infusion in the vein of Marshall (EIVM) has shown to be effective for treating atrial fibrillation (AF) and perimitral left atrial (LA) flutter (PMLAF). Aims To assess the persistence of LA lesions created by EIVM by electro-anatomical mapping (EAM) at repeated procedure for recurrent atrial tachycardia (AT) or AF. Methods We included consecutive patients who underwent EIVM then repeated CA for recurrent AT or AF with high-definition EAM in a single center. Acute and long term EIVM effect was assessed at the index and redo procedures by comparing the area of bipolar voltage <0.05 mV in the vein of Marshall (VOM) region before, immediately after and late after EIVM. Results 24 consecutive patients (mean age 68.6±6.1 years, 58% men) underwent redo procedure after previous successful EIVM for persistent AF (n=21; 88%) or PMLAF (n=5; 21%). In each case, EIVM had an acute effect, with a post-EIVM scar in the VOM (median 12.4 cm2 [interquartile range (IQR) 7.6–15.7]). Mitral isthmus (MI) bidirectional block was obtained in 20/24 patients (83%). In each patient, the EIVM-related lesion persisted, with a chronic scar in the VOM region (median 13.1 cm2 [IQR 8.1–15.9]). One quarter of patients (5/20) had late MI reconnection, which was located at the mitral annulus edge or in the coronary sinus. Conclusions Atrial lesions created by EIVM are durable, which reinforces the efficacy profile of EIVM. Reconduction sites in the MI are located at the edge of the mitral annulus and in the coronary sinus.

Background: High-density automated mapping of complex atrial tachycardias (ATs) requires accurate assessment of activation maps. A new local activation display module (HD Coloring, Biosense Webster®) provides higher map resolution, a better delineation of potential block reducing color interpolation, and a new propagation display. We evaluated the accuracy of a dedicated local activation display compared to standard algorithm. Methods: High density maps from 10 organized atrial tachycardias were collected with a multipolar catheter and were displayed with standard activation or HD Coloring. Six blinded expert operators retrospectively analyzed activation maps and were asked to define (1) the tachycardia mechanism, (2) ablation target, and (3) level of difficulty to interpret those maps. Results: Using HD Coloring, operators were able to reach a correct diagnosis in 93% vs. 63%, p<0.05 compared to standard activation maps. Time to diagnosis was shorter 1.9±1.0 min vs. 3.9±2.1 min, p<0.05. Confidence level would have allowed ablation without necessity for entrainment maneuvers in 87% vs. 53%, p<0.05. Operators would have needed to remap or proceed with multiple entrainments in 3% vs. 13% of cases, p<0.05. Finally, ablation strategy was more accurately identified in 97% vs. 67%, p<0.05. Conclusion: Activation mapping with the new HD Coloring Module allowed a more accurate, reliable, and faster interpretation of complex ATs mechanisms compared to standard activation maps.

Introduction: The success rate of cavo-tricuspid isthmus (CTI) ablation to treat right common flutter is high, up to 95%, but needs bidirectional block confirmation, requiring 2 or 3 catheters. We describe a new pacing technic using a single catheter to ablate and confirm CTI block with differential PR interval measurements. Methods: We included 61 patients from 5 centers that were referred for CTI ablation. All patients had CTI ablation and the CTI block was confirmed by differential pacing using 2 or 3 catheters. The new method consisted in measuring PR interval on the surface ECG using pacing from the tip of ablation catheter on the lateral side (lateral delay) and septal side (coronary sinus ostium) of the CTI line (difference =delta PR interval) before and after CTI ablation. We analyzed the value of delta PR interval to predict bidirectional CTI block as confirmed by standard methods. Results: Among our patient’s population (63±12 years-old), 39 patients were ablated during sinus rhythm while 22 during common flutter. CTI block was achieved in all patients but one. Then, Lateral delay and delta PR interval increased significantly after validation of CTI block (257±42ms vs 318±50ms and 32±23 vs 96±22ms, p<0.0001, respectively). A cut-off ≥70ms of delta PR interval had a 100% of sensitivity and specificity to predict bidirectional CTI block. Conclusion: A single catheter ablation approach to perform CTI line based on surface ECG PR interval measurement is feasible. After ablation, CTI block