P400Spatial relationship between atrial fibrillation drivers identified by dipole density mapping and left atrial fibrosis

Background Atrial fibrillation (AF) is a complex arrhythmia and several mechanisms that might coexist have been proposed. Recent technical advances opened the way to better mapping possibilities and might contribute to target more specific components of the AF substrate. Objective The aim of this study was to evaluate a spatial correlation between AF drivers as determined by a novel non-contact unipolar high-resolution system and atrial fibrosis assessed by cardiac magnetic resonance imaging (MRI). Methods Patients undergoing a first ablation procedure for persistent AF were included. Prior to ablation, a Late Gadolinium-Enhancement (LGE) MRI was performed to detect the fibrotic atrial tissue. The procedure was performed using a new non-contact unipolar high-resolution system allowing a 3D anatomy reconstruction with a continuous dipole density mapping. Three different wave front patterns were analyzed in the left atrium (LA): 1) focal activity (FA), 2) localized rotational activation (LRA) and 3) localized irregular activation (LIA). The spatial distribution of these AF drivers was analyzed prior to AF ablation. Results A total of 49 patterns in 6 patients were identified, among them 22 FA, 14 LRA and 13 LIA. The posterior (n = 14), anterior wall (n = 13) and roof (n = 8) were identified as predominant driver sites. 31/49 (59%) drivers had a strong correlation with late enhancement in MRI. Most of the LIA, LRA and FA were embedded infibrotic areas (LIA 10/13 (77%); LRA 9/14 (64%) and FA 12/22 (54%). The postero-inferior LA showed the best correlation between drivers and fibrosis, the antero-septal LA the weakest one. Conclusion There is a significant overlap between AF driver regions identified by dipole density mapping and atrial fibrosis assessed by MRI. Most of AF drivers are embedded in fibrotic areas, particularly in case of localized irregular activity and at the posterior LA. Abstract Figure.

P978Core to block: a new ablation strategy for treating persistent atrial fibrillation

Background Ablation strategy targeting the core of atrial fibrillation (AF) rotors alone can lead to both stabilisation and destabilisation of rotational activity. Non-contact dipole density mapping system is designed to rapidly identify dynamic regional atrial activation patterns of interest (API) during AF. Purpose To assess the feasibility of an ablation strategy consisted of pulmonary vein isolation + targeting the core of APIs followed by linear ablation to the nearest non-conducting boundary to treat persistent AF. Methods The ablation strategy includes: 1. Antral pulmonary vein electrical isolation (APVI); 2. APIs (focal, localised rotational and localised irregular activation; Figure1) detection by dipole density mapping; 3. API core ablation followed by linear ablation to the nearest non-conduction barrier (APVI/mitral valve); 4. repeat step 2 and 3 in LA (RA, if necessary) until sinus rhythm is achieved. Results Consecutive 40 persistent AF patients (mean 62±12 years, 29 males, AF duration 10±4 months, LA diameter 42±9 mm) were included from 2 centres. An average of 2.0±0.7 APIs per patient were targeted post-APVI. Acute AF termination by ablation was achieved in 27/40 (68%) patients. The mean ablation time of APVI and “Core to block” was 33±12 mins and 31±22 mins, respectively. No major complication occurred. During a mean follow-up of 12±5 months, 32/40 patients (80%) maintained sinus rhythm. Conclusion APVI + “Core to block” guided by the dipole density mapping is feasible for treating persistent AF. A larger randomised study is needed to test the effectiveness of this ablation strategy. Acknowledgement/Funding None

P3756Diverse activation patterns during persistent atrial fibrillation characterised by dipole density non-contact mapping

Background Global simultaneous recording of activation during atrial fibrillation (AF) can elucidate underlying mechanisms contributing to AF maintenance. A better understanding of these mechanisms may allow for a personalised ablation strategy to treat persistent AF. Purpose To characterise left atrial endocardial activation patterns during AF using a novel non-contact dipole density mapping. Methods Activation patterns were characterised into three sub-types: (i) focal with centrifugal activation (FCA); (ii) localised rotational activation (LRA); (iii) localised irregular activation (LIA). Continuous activation patterns were quantified and distributed in the left atrium. Results A total of 144 persistent AF segments with 1068 activation patterns from 25 patients were analysed. The most common pattern was LIA (63%), which consist of four disparate features: slow conduction (45%), pivoting (30%), collision (16%) and acceleration (7%). LRA was the second commonest pattern (20%). FCA (17%) arose frequently from the PVs/ostia. Continuous AF activations comprise multiple combinations of FCA, LRA and LIA, transitioning from one to the next without a discernible order. Preferential conduction areas were typically seen in mid-anterior (48%) and lower-posterior (40%) walls where dominant activations were made up of LRA and LIA. Conclusion AF is characterised by heterogenous activation patterns that vary between individuals. Clinical implications of individualised ablation strategies guided by dipole density mapping will have to be determined. Acknowledgement/Funding None