Standardising single-frame phase singularity identification algorithms and parameters in phase mapping during human atrial fibrillation

Purpose: Recent investigations failed to reproduce the positive rotor-guided ablation outcomes shown by initial studies for treating persistent atrial fibrillation (persAF). Phase singularity (PS) is an important feature for AF driver detection, but algorithms for automated PS identification differ. We aim to investigate the performance of four different techniques for automated PS detection.Methods: 2048-channel virtual electrogram (VEGM) and electrocardiogram signals were collected for 30 s from ten patients undergoing persAF ablation. QRST-subtraction was performed and VEGMs were processed using sinusoidal wavelet reconstruction. The phase was obtained using Hilbert transform. PSs were detected using four algorithms: 1) 2D image processing based and neighbour-indexing algorithm; 2) 3D neighbour-indexing algorithm; 3) 2D kernel convolutional algorithm estimating topological charge; 4) topological charge estimation on 3D mesh. PS annotations were compared using the structural similarity index (SSIM) and Pearson’s correlation coefficient (CORR). Optimized parameters to improve detection accuracy were found for all four algorithms using Fβ score and 10-fold cross-validation compared with manual annotation. Local clustering with density-based spatial clustering of applications with noise (DBSCAN) was proposed to improve algorithms 3 and 4.Results: The PS density maps created by each algorithm with default parameters were poorly correlated. Phase gradient threshold and search radius (or kernels) were shown to affect PS detections. The processing times for the algorithms were significantly different (pConclusion: AF driver identification is dependent on the PS detection algorithms and their parameters, which could explain some of the inconsistencies in rotor-guided ablation outcomes in different studies. For 3D triangulated meshes, algorithm 4+DBSCAN with optimal parameters was the best solution for real-time, automated PS detection due to accuracy and speed. Similarly, algorithm 3+DBSCAN with optimal parameters is preferred for uniform 2D meshes. Such algorithms – and parameters – should be preferred in future clinical studies for identifying AF drivers and minimising methodological heterogeneities. This would facilitate comparisons in rotor-guided ablation outcomes in future works

Unsupervised Classification of Atrial Electrograms for Electroanatomic Mapping of Human Persistent Atrial Fibrillation

Objective: Ablation treatment for persistent atrial fibrillation (persAF) remains challenging due to the absence of a "ground truth" for atrial substrate characterization and the presence of multiple mechanisms driving the arrhythmia. We implemented an unsupervised classification to identify AEG clusters with similar patterns, which were then validated by AEG-derived markers. Methods: 956 bipolar AEGs were collected from 11 persAF patients. CARTO variables (Biosense Webster; ICL, ACI and SCI) were used to create a 3D space, and subsequently used to perform an unsupervised classification with k-means. The characteristics of the identified groups were investigated using nine AEG-derived markers: sample entropy (SampEn), dominant frequency, organization index (OI), determinism, laminarity, recurrence rate (RR), peak-to-peak (PP) amplitude, cycle length (CL), and wave similarity (WS). Results: Five AEG classes with distinct characteristics were identified (F=582, PConclusions: Our results expand and reinterpret the criteria used for automated AEG classification. The nine markers highlighted electrophysiological differences among the five classes found by the k-means, which could provide a more complete characterization of persAF substrate during ablation target identification in future clinical studies.</div

Could regional electrogram desynchronization identified using mean phase coherence be potential ablation targets in persistent atrial fibrillation?

BackgroundIt remains controversial as to whether rotors detected using phase mapping during persistent atrial fibrillation (persAF) represent main drivers of the underlying mechanism as others found rotors to be located near line of conduction block. Regional electrogram desynchronization (RED) has been suggested as successful targets for persAF ablation, but automatic tools and quantitative measures are lacking.PurposeWe aim to use mean phase coherence (MPC) to automatically identify RED regions during persAF. This method was compared with phase singularity density (PSD) maps.MethodsPatients undergoing left atrial (LA) persAF ablation were enrolled (n = 10). 2048-channel virtual electrograms (VEGMs) were collected from each patient using non-contact mapping (St Jude Velocity System, Ensite Array) for 10 seconds. To remove far field ventricular activities, QRS onset and T wave end locations were detected from ECG lead I (Figure 1A) and only the VEGM segments from T end to QRS onset were included in the analysis. VEGMs were reconstructed using sinusoidal wavelets fitting and the phase of VEGMs determined using Hilbert transform. Phase singularities (PS) were detected using the topological charge method and repetitive PSD maps were generated. RED was defined as the average of MPC of each node against direct neighbouring nodes on the 3D mesh (Figure 1A-B). Linear regression analysis was used to compare the average MPC vs. PSD and vs. the standard deviation of MPC (MPC_SD).ResultsA total of 221,184 VEGM segments were analysed with mean duration of 364.2 milliseconds. MPC has shown the ability to quantify the level of synchronisation between VEGMs (Figure 1B). Inverse correlation was found between PSD and average MPC values for all 10 patients (p ConclusionWe have proposed a method to quantify the level of synchronisation between VEGMs. Phase density mapping showed a considerable agreement with RED regions reflecting regional conducting delays, which supports the previous finding where rotors found at conduction block. Inverse correlation between local average MPC and MPC_SD suggests that conduction delays of the identified regions are not heterogenous, posing directional preferences. Rather than solely looking for rotational activities, this method could identify comprehensive RED regions, which may also explain the conflicting results from different studies targeting rotational activities, where incomplete subsets of RED regions could have been targeted. Atrial RED regions can easily be identified with simultaneously collected electrograms from multi-polar catheters and should be targeted in future persAF studies.</div

Images of Research 2019

Images Of Research 2019 Winners: Yang Chen – ‘Spiral Up and Down’ - Judges’ Prize Winner Dina El-Hamamsy – ‘Where is my patient Patient?’ - Joint Judges’ Prize Runners-up Tom Matheson – ‘Ginormous Genome’ (1) - Joint Judges’ Prize Runners-up Styliano Spathariotis – ‘Girl with a Metallic Earring’ - Katherine May People’s Choice Winner Soheb Mandhai – ‘The Cosmic Dance of Two Neutron Stars’ - People’s Choice Runner-up Brandon Fathy – ‘Speed, Space, and Time’ - Leicester Institute of Advanced Studies Interdisciplinary Prize Images Of Research 2018 submissions: Abbey Ellis – ‘Carving Out an Understanding’ (1) Abbey Ellis – ‘The Art of the Reproduction’ (2) Ahmed Elimam - Untitled Artur Soczawa-Stronczyk – ‘Do the locomotion with me’ Aseel Alfuhied – ‘Cosmic storm in the heart of darkness’ (1) Aseel Alfuhied – ‘Heart to Heart’ (2) Aseel Alfuhied – ‘Pop Heart’ (3) Beatriz Sanchez-Cano – ‘The Sun, our neural connection’ Cesare Cuzzola – ‘Buddha Day 2019’ Charlotte Barratt – ‘Sound’ (1) Charlotte Barratt – ‘Girl Praying’ (2) Chris Allen – ‘Perceptions and Realities: Building Community Resilience Against Extremism’ (1) Chris Allen – ‘Perceptions and Realities: Building Community Resilience Against Extremism’ (2) David Unwin – ‘Death flight’ Diane Urquhart – ‘Laying ghosts to rest’ Eloisa Rodrigues – ‘Tropical self-portrait’ Fernando Schlindwein – ‘Chaos in the heart’ (1) Fernando Schlindwein – ‘Porcupine’ (2) Graham Frobisher – ‘The 7th Decade Manager’ Hanna McQuail – ‘That colossal wreck, boundless and bare’ Hatice Kayman – ‘Immigrants have opportunities to do their festivals in London’ Hedwig Krawczyk – ‘Underwater Time Machines’ Hipolito Treffinger – ‘Layers’ Jacqueline Taylor – ‘Miriam Haughton at the British Academy’ Jan Vandeburie – ‘Dress to Impress’ Jennifer Beamer – ‘Human-Animal Relationships in Weaving’ John Goodwin – ‘Slow Sociology in South Wigston’ Kinga Kolodziej – ‘In a blink of an eye…’ (1) Kinga Kolodziej – ‘In a blink of an eye…’ (2) Kristina Wright – ‘Janus-Faced Seoul’ Kseniia Bondarenko – ‘Your brain drives me crazy’ (1) Kseniia Bondarenko – ‘Your brain drives me crazy’ (2) Liam Crawford – ‘The heartfelt love story between one nanoparticle and another’ Lisa Huddlestone – ‘Seeing the wood and the trees’ (1) Lisa Huddlestone – ‘Seeing the wood and the trees’ (2) Margarita Avgerinopoulou – ‘A dash of magic’ (1) Margarita Avgerinopoulou – ‘Fantasy at the making’ (2) Martha Papadopoulou – ‘The power of a drop’ (1) Martha Papadopoulou – ‘Every drop counts’! (2) Mayamin Altae - Untitled (or the Tennyson quote) Michael Curtis – ‘The arrival of the shoreline detective’ (1) Michael Curtis – ‘The arrival of the shoreline detective’ (2) Neelam Dave – ‘The damage bacteria can do’ Neil Harris – ‘Colour amongst the chaos’ Nitu Gupta – ‘Far Beyond Insecurities’ Nora Ngii Musyoka – ‘She’s Just the Other Half of Me’ Nukul Charlin – ‘Why are Ladyboy Tolerated in Thai Society?’ Pariyakorn Petkaew – ‘Be silent…Be thinking’ Rachel Belben – ‘Ardeadactylus longicollum’ (1) Rachel Belben – ‘Psittacosaurus’ (2) Roberto Sommariva - Untitled Saima Ahmad – ‘The Command Centre’ (1) Saima Ahmad – ‘Vial do you see it?’ (2) Saima Ahmad – ‘Beyond the Canopy’ (3) Samuel J Perry – ‘Metallic snowflakes’ (1) Samuel J Perry – ‘Metallic snowflakes’ (2) Stephanie Bowry – ‘Storm Clouds over Vaux-le-Vicomte’ Tom Matheson – ‘Ginormous Genome’ (2) Yewande Okuleye – ‘Commemoration, Remembrance and Bodies of Evidence’ Yewande Okuleye, Robert Garner – ‘From pain to pleasure: We no longer just eat our greens, it’s imperative to photograph share and like on Instagram.’ (1) Yewande Okuleye, Robert Garner – ‘A green plaque for animal ethics?’ (2) Yewande Okuleye, Robert Garner – ‘A green plaque for animal ethics?’ (3)</p