P982High density mapping in atrial tachycardia after previous ablation of persistent atrial fibrillation. A tool to reveal the pathomechanism and the target for successful ablation
Authors: Vogtmann T , Boye P , Janssen G 
Published: October 2019

Abstract

Introduction
Recurrent atrial tachycardias (AT) after ablation of persistent atrial fibrillation (AF) including substrate modification on top of pulmonary vein isolation (PVI) only, are complex and challenging procedures. Key to an effective reablation is the understanding of the individual pathomechanism and therewith identification of proper ablation targets. The aim of this study was to evaluate the potential of 3-D high density mapping to better define the underlying tachy-mechanism and develop individual successful ablation strategies.

Methods
31 consecutive patients (pts) with stable ATs were prospectively included. High density activation mapping was performed with a 3-D mapping system using a mapping catheter with 5 arms equipped with 4 electrodes (2–6-2 spacing) each. The activation mapping was performed using software supported automated mapping (Tissue proximity indication on, strict to moderate settings for position and local activation time settings) aiming for a minimum of 2000 mapping points with minimum density of 1mm. The maps were analyzed and an ablation strategy developed based on the suspected AT mechanism. Acute success was defined as termination of the arrhythmia during ablation following the initial strategy: in focal AT, termination with ≤3 ablations in the predefined area. In macroreentry tachycardia, termination during completion of predefined linear target.

Results
31 pts (16 f/15 m), age 68±9 y with ECG diagnosed AT after ablation of persistent AF were included. At baseline patients had undergone a mean of 2.2 (range 1 to 6) ablation procedures for persistent AF with the first procedure performed 2,2 y (range 3 mon– 8 y) earlier. In 81% of the pts additional ablations (≥3 lines and/or rotor ablation) were added to PVI and/or Re-PVI in earlier procedures. 41 ATs in 31 pts with a mean cycle length of 328 ms (range 200 to 580 ms) were analyzed: 58% macroreentries (24/41), 22% microreentries (9), 10% focal (4). 4 AT maps were inconclusive (3 after multiple previous ablations and in one patient due to multiple alternating ATs, 1 was defined focal in retrospective analysis). All 13 ATs with focal / microreentrant pattern were successfully ablated with ≤3 ablations and 18/24 of the macroreentries with the line attempted first after identification of an isthmus or zone of slow conduction. This adds up to an 84% (31/37) acute success rate of ablation of the identified ablation target and a first attempt success of 76% of all ATs mapped. The total procedure time was 134±43 min (60 to 220 min), fluoroscopy 17±9 min. With a mean FU of 8±6 mon (range 4–25 mon) success was 61%, defined freedom of recurrence without antiarrhythmic drugs.

Conclusion
High density mapping of recurrent ATs after ablation of persistent AF is an effective tool to reveal the pathomechanism of the tachycardia and develop an effective individual ablation strategy in complex substrates with a high acute and mid-term success rate.