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Thronsen E, Bergh T, Thorsen TI, Christiansen EF, Frafjord J, Crout P, van Helvoort ATJ, Midgley PA, Holmestad R. Scanning precession electron diffraction data analysis approaches for phase mapping of precipitates in aluminium alloys. Ultramicroscopy 2024; 255:113861. [PMID: 37852158 DOI: 10.1016/j.ultramic.2023.113861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/22/2023] [Accepted: 09/27/2023] [Indexed: 10/20/2023]
Abstract
Mapping the spatial distribution of crystal phases with nm-scale spatial resolution is an important characterisation task in studies of multi-phase materials. One popular approach is to use scanning precession electron diffraction which enables semi-automatic phase mapping at the nanoscale by collecting a single precession electron diffraction pattern at every probe position over regions spanning up to a few micrometers. For a successful phase mapping each diffraction pattern must be correctly identified. In this work four different approaches for phase mapping of embedded precipitates in an Al-Cu-Li alloy are compared on a sample containing three distinct crystal phases. These approaches are based on: non-negative matrix factorisation, vector matching, template matching and artificial neural networks. To evaluate the success of each approach a ground truth phase map was manually created from virtual images based on characteristic phase morphologies and compared with the deduced phase maps. The percentage accuracy of all methods when compared to the ground truth was satisfactory, with all approaches obtaining scores above 98%. The optimal method depends on the specific task at hand. Non-negative matrix factorisation is suitable with limited prior data knowledge but performs best with few unique diffraction patterns and requires substantial post-processing. It has the advantage of reducing the dimensionality of the dataset and handles weak diffracted intensities well given that they occur repeatedly. The current vector matching implementation is fast, simple, based only on the Bragg spot geometry and requires few parameters. It does however demand that each Bragg spot is accurately detected in each pattern and the current implementation is limited to zone axis patterns. Template matching handles a large range of orientations, including off-axis patterns. However, achieving successful and reliable results often require thorough data pre-processing and do require adequate diffraction simulations. For artificial neural networks a substantial setup effort is demanded but once trained it excels for routine tasks, offering fast predictions. The implemented codes and the data used are available open-source. These resources and the detailed assessment of the methods will allow others to make informed decisions when selecting a data analysis approach for 4D-STEM phase mapping tasks on other material systems.
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Affiliation(s)
- E Thronsen
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway; Materials and Nanotechnology, SINTEF Industry, N-7465, Trondheim, Norway.
| | - T Bergh
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway; Department of Chemical Engineering, NTNU, N-7491 Trondheim, Norway
| | - T I Thorsen
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
| | - E F Christiansen
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
| | - J Frafjord
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
| | - P Crout
- Department of Materials Science and Metallurgy, University of Cambridge, CB3 0FS Cambridge, UK
| | - A T J van Helvoort
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
| | - P A Midgley
- Department of Materials Science and Metallurgy, University of Cambridge, CB3 0FS Cambridge, UK
| | - R Holmestad
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
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Abstract
Drivers are increasingly studied ablation targets for atrial fibrillation (AF). However, results from ablation remain controversial. First, outcomes vary between centers and patients. Second, it is unclear how best to perform driver ablation. Third, there is a lack of practical guidance on how to identify critical from secondary sites using different AF mapping methods. This article addresses each of these issues.
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Affiliation(s)
- Junaid Zaman
- Stanford University, 780 Welch Road, Suite CJ250F, Stanford, CA 94305, USA; Imperial College London, London, UK
| | - Tina Baykaner
- Department of Medicine/Cardiovascular Medicine, Stanford University, 780 Welch Road, Suite CJ250F, Stanford, CA 94305, USA
| | - Sanjiv M Narayan
- Department of Medicine/Cardiovascular Medicine and Cardiovascular Institute, Stanford University, 780 Welch Road, Suite CJ250F, MC 5773, Stanford, CA 94305, USA.
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Costoya-Sánchez A, Climent AM, Hernández-Romero I, Liberos A, Fernández-Avilés F, Narayan SM, Atienza F, Guillem MS, Rodrigo M. Automatic quality electrogram assessment improves phase-based reentrant activity identification in atrial fibrillation. Comput Biol Med 2020; 117:103593. [PMID: 32072974 PMCID: PMC10984645 DOI: 10.1016/j.compbiomed.2019.103593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 12/20/2019] [Accepted: 12/23/2019] [Indexed: 11/30/2022]
Abstract
Identification of reentrant activity driving atrial fibrillation (AF) is increasingly important to ablative therapies. The goal of this work is to study how the automatically-classified quality of the electrograms (EGMs) affects reentrant AF driver localization. EGMs from 259 AF episodes obtained from 29 AF patients were recorded using 64-poles basket catheters and were manually classified according to their quality. An algorithm capable of identifying signal quality was developed using time and spectral domain parameters. Electrical reentries were identified in 3D phase maps using phase transform and were compared with those obtained with a 2D activation-based method. Effect of EGM quality was studied by discarding 3D phase reentries detected in regions with low-quality EGMs. Removal of reentries identified by 3D phase analysis in regions with low-quality EGMs improved its performance, increasing the area under the ROC curve (AUC) from 0.69 to 0.80. The EGMs quality classification algorithm showed an accurate performance for EGM classification (AUC 0.94) and reentry detection (AUC 0.80). Automatic classification of EGM quality based on time and spectral signal parameters is feasible and accurate, avoiding the manual labelling. Discard of reentries identified in regions with automatically-detected poor-quality EGMs improved the specificity of the 3D phase-based method for AF driver identification.
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Affiliation(s)
| | - Andreu M Climent
- ITACA Institute, Universitat Politècnica de València, Spain; Cardiology Department, Hospital General Universitario Gregorio Marañón, IiSGM, CIBERCV, Spain
| | | | | | | | | | - Felipe Atienza
- Cardiology Department, Hospital General Universitario Gregorio Marañón, IiSGM, CIBERCV, Spain
| | | | - Miguel Rodrigo
- ITACA Institute, Universitat Politècnica de València, Spain.
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Lunt A, Salvati E, Baimpas N, Dolbnya I, Neo TK, Korsunsky AM. Investigations into the interface failure of yttria partially stabilised zirconia - porcelain dental prostheses through microscale residual stress and phase quantification. Dent Mater 2019; 35:1576-93. [PMID: 31522759 DOI: 10.1016/j.dental.2019.08.098] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 08/15/2019] [Indexed: 11/22/2022]
Abstract
OBJECTIVES Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional toughness. Within these components the residual stress and crystallographic phase of YPSZ close to the interface are highly influential in the primary failure mode; near interface porcelain chipping. In order to improve present understanding of this behaviour, characterisation of these parameters is needed at an improved spatial resolution. METHODS In this study transmission micro-focus X-ray Diffraction, Raman spectroscopy, and focused ion beam milling residual stress analysis techniques have, for the first time, been used to quantify and cross-validate the microscale spatial variation of phase and residual stress of YPSZ in a prosthesis cross-section. RESULTS The results of all techniques were found to be comparable and complementary. Monoclinic YPSZ was observed within the first 10μm of the YPSZ-porcelain interface with a maximum volume fraction of 60%. Tensile stresses were observed within the first 150 μm of the interface with a maximum value of ≈300 MPa at 50 μm from the interface. The remainder of the coping was in mild compression at ≈-30MPa, with shear stresses of a similar magnitude also being induced by the YPSZ phase transformation. SIGNIFICANCE The analysis indicates that the interaction between phase transformation, residual stress and porcelain creep at YPSZ-porcelain interface results in a localised porcelain fracture toughness reduction. This explains the increased propensity of failure at this location, and can be used as a basis for improving prosthesis design.
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Baykaner T, Zaman JAB, Rogers AJ, Navara R, AlHusseini M, Borne RT, Park S, Wang PJ, Krummen DE, Sauer WH, Narayan SM. Spatial relationship of sites for atrial fibrillation drivers and atrial tachycardia in patients with both arrhythmias. Int J Cardiol 2017; 248:188-195. [PMID: 28733070 PMCID: PMC5865446 DOI: 10.1016/j.ijcard.2017.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Revised: 06/21/2017] [Accepted: 07/03/2017] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Atrial fibrillation (AF) often converts to and from atrial tachycardia (AT), but it is undefined if these rhythms are mechanistically related in such patients. We tested the hypothesis that critical sites for AT may be related to regional AF sources in patients with both rhythms, by mapping their locations and response to ablation on transitions to and from AF. METHODS From 219 patients undergoing spatial mapping of AF prior to ablation at 3 centers, we enrolled 26 patients in whom AF converted to AT by ablation (n=19) or spontaneously (n=7; left atrial size 42±6cm, 38% persistent AF). Both atria were mapped in both rhythms by 64-electrode baskets, traditional activation maps and entrainment. RESULTS Each patient had a single mapped AT (17 reentrant, 9 focal) and 3.7±1.7 AF sources. The mapped AT spatially overlapped one AF source in 88% (23/26) of patients, in left (15/23) or right (8/23) atria. AF transitioned to AT by 3 mechanisms: (a) ablation anchoring AF rotor to AT (n=13); (b) residual, unablated AF source producing AT (n=6); (c) spontaneous slowing of AF rotor leaving reentrant AT at this site without any ablation (n=7). Electrogram analysis revealed a lower peak-to-peak voltage at overlapping sites (0.36±0.2mV vs 0.49±0.2mV p=0.03). CONCLUSIONS Mechanisms responsible for AT and AF may arise in overlapping atrial regions. This mechanistic inter-relationship may reflect structural and/or functional properties in either atrium. Future work should delineate how acceleration of an organized AT may produce AF, and whether such regions can be targeted a priori to prevent AT recurrence post AF ablation.
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Affiliation(s)
- Tina Baykaner
- Stanford University Medical Center, Palo Alto, CA, United States.
| | - Junaid A B Zaman
- Stanford University Medical Center, Palo Alto, CA, United States
| | - Albert J Rogers
- Stanford University Medical Center, Palo Alto, CA, United States
| | - Rachita Navara
- Stanford University Medical Center, Palo Alto, CA, United States
| | | | - Ryan T Borne
- University of Colorado School of Medicine, Denver, CO, United States
| | - Shirley Park
- Stanford University Medical Center, Palo Alto, CA, United States
| | - Paul J Wang
- Stanford University Medical Center, Palo Alto, CA, United States
| | - David E Krummen
- University of California San Diego and Veterans Affairs Medical Center, La Jolla, CA, United States
| | - William H Sauer
- University of Colorado School of Medicine, Denver, CO, United States
| | - Sanjiv M Narayan
- Stanford University Medical Center, Palo Alto, CA, United States
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Pathik B, Kalman JM, Walters T, Kuklik P, Zhao J, Madry A, Sanders P, Kistler PM, Lee G. Absence of rotational activity detected using 2-dimensional phase mapping in the corresponding 3-dimensional phase maps in human persistent atrial fibrillation. Heart Rhythm 2017; 15:182-192. [PMID: 28917553 DOI: 10.1016/j.hrthm.2017.09.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 01/07/2023]
Abstract
BACKGROUND Current phase mapping systems for atrial fibrillation create 2-dimensional (2D) maps. This process may affect the accurate detection of rotors. We developed a 3-dimensional (3D) phase mapping technique that uses the 3D locations of basket electrodes to project phase onto patient-specific left atrial 3D surface anatomy. OBJECTIVE We sought to determine whether rotors detected in 2D phase maps were present at the corresponding time segments and anatomical locations in 3D phase maps. METHODS One-minute left atrial atrial fibrillation recordings were obtained in 14 patients using the basket catheter and analyzed off-line. Using the same phase values, 2D and 3D phase maps were created. Analysis involved determining the dominant propagation patterns in 2D phase maps and evaluating the presence of rotors detected in 2D phase maps in the corresponding 3D phase maps. RESULTS Using 2D phase mapping, the dominant propagation pattern was single wavefront (36.6%) followed by focal activation (34.0%), disorganized activity (23.7%), rotors (3.3%), and multiple wavefronts (2.4%). Ten transient rotors were observed in 9 of 14 patients (64%). The mean rotor duration was 1.1 ± 0.7 seconds. None of the 10 rotors observed in 2D phase maps were seen at the corresponding time segments and anatomical locations in 3D phase maps; 4 of 10 corresponded with single wavefronts in 3D phase maps, 2 of 10 with 2 simultaneous wavefronts, 1 of 10 with disorganized activity, and in 3 of 10 there was no coverage by the basket catheter at the corresponding 3D anatomical location. CONCLUSION Rotors detected in 2D phase maps were not observed in the corresponding 3D phase maps. These findings may have implications for current systems that use 2D phase mapping.
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Affiliation(s)
- Bhupesh Pathik
- Royal Melbourne Hospital, Parkville, Victoria, Australia; University of Melbourne, Parkville, Victoria, Australia
| | - Jonathan M Kalman
- Royal Melbourne Hospital, Parkville, Victoria, Australia; University of Melbourne, Parkville, Victoria, Australia
| | - Tomos Walters
- Royal Melbourne Hospital, Parkville, Victoria, Australia; University of Melbourne, Parkville, Victoria, Australia
| | - Pawel Kuklik
- University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Andrew Madry
- Royal Melbourne Hospital, Parkville, Victoria, Australia
| | - Prashanthan Sanders
- Royal Adelaide Hospital, University of Adelaide, Adelaide, South Australia, Australia
| | - Peter M Kistler
- University of Melbourne, Parkville, Victoria, Australia; Alfred Hospital and Baker IDI, Melbourne, Victoria, Australia
| | - Geoffrey Lee
- Royal Melbourne Hospital, Parkville, Victoria, Australia; University of Melbourne, Parkville, Victoria, Australia.
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Li X, Salinet JL, Almeida TP, Vanheusden FJ, Chu GS, Ng GA, Schlindwein FS. An interactive platform to guide catheter ablation in human persistent atrial fibrillation using dominant frequency, organization and phase mapping. Comput Methods Programs Biomed 2017; 141:83-92. [PMID: 28241971 DOI: 10.1016/j.cmpb.2017.01.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 01/05/2017] [Accepted: 01/17/2017] [Indexed: 06/06/2023]
Abstract
BACKGROUND AND OBJECTIVE Optimal targets for persistent atrial fibrillation (persAF) ablation are still debated. Atrial regions hosting high dominant frequency (HDF) are believed to participate in the initiation and maintenance of persAF and hence are potential targets for ablation, while rotor ablation has shown promising initial results. Currently, no commercially available system offers the capability to automatically identify both these phenomena. This paper describes an integrated 3D software platform combining the mapping of both frequency spectrum and phase from atrial electrograms (AEGs) to help guide persAF ablation in clinical cardiac electrophysiological studies. METHODS 30s of 2048 non-contact AEGs (EnSite Array, St. Jude Medical) were collected and analyzed per patient. After QRST removal, the AEGs were divided into 4s windows with a 50% overlap. Fast Fourier transform was used for DF identification. HDF areas were identified as the maximum DF to 0.25Hz below that, and their centers of gravity (CGs) were used to track their spatiotemporal movement. Spectral organization measurements were estimated. Hilbert transform was used to calculate instantaneous phase. RESULTS The system was successfully used to guide catheter ablation for 10 persAF patients. The mean processing time was 10.4 ± 1.5min, which is adequate comparing to the normal electrophysiological (EP) procedure time (120∼180min). CONCLUSIONS A customized software platform capable of measuring different forms of spatiotemporal AEG analysis was implemented and used in clinical environment to guide persAF ablation. The modular nature of the platform will help electrophysiological studies in understanding of the underlying AF mechanisms.
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Affiliation(s)
- Xin Li
- Department of Engineering, University of Leicester, UK; Department of Cardiovascular Science, University of Leicester, UK
| | - João L Salinet
- Biomedical Engineering, Center for Engineering, Modelling and Applied Social Sciences, Universidade Federal do ABC, Brazil; Bioengineering Division, Heart Institute (InCor), Brasil
| | - Tiago P Almeida
- Department of Engineering, University of Leicester, UK; Biomedical Engineering, Center for Engineering, Modelling and Applied Social Sciences, Universidade Federal do ABC, Brazil
| | | | - Gavin S Chu
- Department of Cardiovascular Science, University of Leicester, UK; University Hospitals of Leicester NHS Trust, UK
| | - G André Ng
- Department of Cardiovascular Science, University of Leicester, UK; University Hospitals of Leicester NHS Trust, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, UK
| | - Fernando S Schlindwein
- Department of Engineering, University of Leicester, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, UK.
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Wang L, Gharbia OA, Horáček BM, Sapp JL. Noninvasive epicardial and endocardial electrocardiographic imaging of scar-related ventricular tachycardia. J Electrocardiol 2016; 49:887-893. [PMID: 27968777 DOI: 10.1016/j.jelectrocard.2016.07.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the re-entry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites. METHODS For patients who underwent catheter ablation of scar-related VT, CT scan was obtained prior to the ablation procedure and 120-lead body-surface electrocardiograms (ECGs) were acquired during induced VTs. These data were used for noninvasive ECG imaging to computationally reconstruct electrical potentials on the epicardium and on the endocardium of both ventricles. Activation time and phase maps of the VT circuit were extracted from the reconstructed electrograms. They were analyzed with respect to scar substrate obtained from catheter mapping, as well as VT exits confirmed through ablation sites that successfully terminated the VT. RESULTS The reconstructed re-entry circuits correctly revealed both epicardial and endocardial origins of activation, consistent with locations of exit sites confirmed from the ablation procedure. The temporal dynamics of the re-entry circuits, particularly the slowing of conduction as indicated by the crowding and zig-zag conducting of the activation isochrones, collocated well with scar substrate obtained by catheter voltage maps. Furthermore, the results indicated that some re-entry circuits involve both the epicardial and endocardial layers, and can only be properly interpreted by mapping both layers simultaneously. CONCLUSIONS This study investigated the potential of ECG-imaging for beat-to-beat mapping of unstable reentrant circuits. It shows that simultaneous epicardial and endocardial mapping may improve the delineation of the 3D spatial construct of a re-entry circuit and its exit. It also shows that the use of phase mapping can reveal regions of slow conduction that collocate well with suspected heterogeneous regions within and around the scar.
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Affiliation(s)
- Linwei Wang
- Rochester Institute of Technology, Rochester, NY, USA.
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Sasaki N, Okumura Y, Watanabe I, Madry A, Hamano Y, Nikaido M, Kogawa R, Nagashima K, Takahashi K, Iso K, Ohkubo K, Nakai T, Hirayama A. Localized rotors and focal impulse sources within the left atrium in human atrial fibrillation: A phase analysis of contact basket catheter electrograms. J Arrhythm 2016; 32:141-4. [PMID: 27092196 PMCID: PMC4823606 DOI: 10.1016/j.joa.2015.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 11/11/2015] [Accepted: 11/27/2015] [Indexed: 12/05/2022] Open
Abstract
Background Consistent detection of rotor(s) and/or focal impulse(s) of atrial fibrillation can using a 64-pole basket catheter remain unclear. Methods and results Intracardiac left atrial electrograms were recorded, prior to ablation, in 20 patients with atrial fibrillation. Unipolar electrograms, filtered at 0.1–300 Hz, were recorded and exported for an offline phase analysis. From the cohort, 8 of the 20 patients had analyzable data. Localized rotors were identified in 3 of these patients, with focal impulses detected in 4 patients. Conclusion Localized rotors and focal impulses can be identified on phase maps of atrial fibrillation in a small number of patients.
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Affiliation(s)
- Naoko Sasaki
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Yasuo Okumura
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Ichiro Watanabe
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | | | | | | | - Rikitake Kogawa
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Koichi Nagashima
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Keiko Takahashi
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Kazuki Iso
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Kimie Ohkubo
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Toshiko Nakai
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Atsushi Hirayama
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
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Guillem MS, Climent AM, Rodrigo M, Fernández-Avilés F, Atienza F, Berenfeld O. Presence and stability of rotors in atrial fibrillation: evidence and therapeutic implications. Cardiovasc Res 2016; 109:480-92. [PMID: 26786157 DOI: 10.1093/cvr/cvw011] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 01/15/2016] [Indexed: 01/08/2023] Open
Abstract
Rotor-guided ablation has opened new perspectives into the therapy of atrial fibrillation (AF). Analysis of the spatio-temporal cardiac excitation patterns in the frequency and phase domains has demonstrated the importance of rotors in research models of AF, however, the dynamics and role of rotors in human AF are still controversial. In this review, the current knowledge gained through research models and patient data that support the notion that rotors are key players in AF maintenance is summarized. We report and discuss discrepancies regarding rotor prevalence and stability in various studies, which can be attributed in part to methodological differences among mapping systems. Future research for validation and improvement of current clinical electrophysiology mapping technologies will be crucial for developing mechanistic-based selection and application of the best therapeutic strategy for individual AF patient, being it, pharmaceutical, ablative, or other approach.
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Affiliation(s)
- María S Guillem
- ITACA, Universitat Politèscnica de València, Valencia, Spain
| | - Andreu M Climent
- Hospital General Universitario Gregorio Marañón, Madrid, Spain Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain
| | - Miguel Rodrigo
- ITACA, Universitat Politèscnica de València, Valencia, Spain
| | - Francisco Fernández-Avilés
- Hospital General Universitario Gregorio Marañón, Madrid, Spain Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain Facultad de Medicina, Universidad Complutense de Madrid, Spain
| | - Felipe Atienza
- Hospital General Universitario Gregorio Marañón, Madrid, Spain Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain Facultad de Medicina, Universidad Complutense de Madrid, Spain
| | - Omer Berenfeld
- Center for Arrhythmia Research, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109, USA
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Gonzales MJ, Vincent KP, Rappel WJ, Narayan SM, McCulloch AD. Structural contributions to fibrillatory rotors in a patient-derived computational model of the atria. Europace 2015; 16 Suppl 4:iv3-iv10. [PMID: 25362167 DOI: 10.1093/europace/euu251] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
AIMS The aim of this study was to investigate structural contributions to the maintenance of rotors in human atrial fibrillation (AF) and possible mechanisms of termination. METHODS AND RESULTS A three-dimensional human biatrial finite element model based on patient-derived computed tomography and arrhythmia observed at electrophysiology study was used to study AF. With normal physiological electrical conductivity and effective refractory periods (ERPs), wave break failed to sustain reentrant activity or electrical rotors. With depressed excitability, decreased conduction anisotropy, and shorter ERP characteristic of AF, reentrant rotors were readily maintained. Rotors were transiently or permanently trapped by fibre discontinuities on the lateral wall of the right atrium near the tricuspid valve orifice and adjacent to the crista terminalis, both known sites of right atrial arrhythmias. Modelling inexcitable regions near the rotor tip to simulate fibrosis anchored the rotors, converting the arrhythmia to macro-reentry. Accordingly, increasing the spatial core of inexcitable tissue decreased the frequency of rotation, widened the excitable gap, and enabled an external wave to impinge on the rotor core and displace the source. CONCLUSION These model findings highlight the importance of structural features in rotor dynamics and suggest that regions of fibrosis may anchor fibrillatory rotors. Increasing extent of fibrosis and scar may eventually convert fibrillation to excitable gap reentry. Such macro-reentry can then be eliminated by extending the obstacle or by external stimuli that penetrate the excitable gap.
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Affiliation(s)
- Matthew J Gonzales
- Department of Bioengineering, University of California San Diego, Mail Code 0412, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA
| | - Kevin P Vincent
- Department of Bioengineering, University of California San Diego, Mail Code 0412, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA
| | - Wouter-Jan Rappel
- Department of Physics, University of California San Diego, La Jolla, CA, USA Center for Theoretical Biological Physics, University of California San Diego, La Jolla, CA, USA
| | - Sanjiv M Narayan
- Department of Medicine, University of California San Diego, La Jolla, CA, USA Cardiac Biomedical Science and Engineering Center, University of California San Diego, CA, USA VA San Diego Healthcare System, San Diego, CA, USA
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego, Mail Code 0412, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA Department of Medicine, University of California San Diego, La Jolla, CA, USA Cardiac Biomedical Science and Engineering Center, University of California San Diego, CA, USA
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Pashaei A, Bayer J, Meillet V, Dubois R, Vigmond E. Computation and projection of spiral wave trajectories during atrial fibrillation: a computational study. Card Electrophysiol Clin 2015; 7:37-47. [PMID: 25784021 DOI: 10.1016/j.ccep.2014.11.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To show how atrial fibrillation rotor activity on the heart surface manifests as phase on the torso, fibrillation was induced on a geometrically accurate computer model of the human atria. The Hilbert transform, time embedding, and filament detection were compared. Electrical activity on the epicardium was used to compute potentials on different surfaces from the atria to the torso. The Hilbert transform produces erroneous phase when pacing for longer than the action potential duration. The number of phase singularities, frequency content, and the dominant frequency decreased with distance from the heart, except for the convex hull.
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Affiliation(s)
- Ali Pashaei
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France.
| | - Jason Bayer
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Valentin Meillet
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Rémi Dubois
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Edward Vigmond
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Bordeaux Institute of Mathematics UMR 5251, University of Bordeaux, 351 cours de la Libération, Talence 33405, France
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Atienza F, Climent AM, Guillem MS, Berenfeld O. Frontiers in Non-invasive Cardiac Mapping: Rotors in Atrial Fibrillation-Body Surface Frequency- Phase Mapping. Card Electrophysiol Clin 2015; 7:59-69. [PMID: 25729463 DOI: 10.1016/j.ccep.2014.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Experimental and clinical data demonstrate that atrial fibrillation (AF) maintenance in animals and groups of patients depends on localized reentrant sources localized primarily to the pulmonary veins (PVs) and the left atrium(LA) posterior wall in paroxysmal AF but elsewhere, including the right atrium (RA), in persistent AF. Moreover, AF can be eliminated by directly ablating AF-driving sources or "rotors," that exhibit high-frequency, periodic activity. The RADAR-AF randomized trial demonstrated that an ablation procedure based on a more target-specific strategy aimed at eliminating high frequency sites responsible for AF maintenance is as efficacious as and safer than empirically isolating all the PVs. In contrast to the standard ECG, global atrial noninvasive frequency analysis allows non-invasive identification of high-frequency sources before the arrival at the electrophysiology laboratory for ablation. Body surface potential map (BSPM) replicates the endocardial distribution of DFs with localization of the highest DF (HDF) and can identify small areas containing the high-frequency sources. Overall, BSPM had a sensitivity of 75% and specificity of 100% for capturing intracardiac EGMs as having LARA DF gradient. However, raw BSPM data analysis of AF patterns of activity showed incomplete and instable reentrant patterns of activation. Thus, we developed an analysis approach whereby a narrow band-pass filtering allowed selecting the electrical activity projected on the torso at the HDF, which stabilized the projection of rotors that potentially drive AF on the surface. Consequently, driving reentrant patterns ("rotors") with spatiotemporal stability during >70% of the AF time could be observed noninvasibly after HDF-filtering. Moreover, computer simulations found that the combination of BSPM phase mapping with DF analysis enabled the discrimination of true rotational patterns even during the most complex AF. Altogether, these studies show that the combination of DF analysis with phase maps of HDF-filtered surface ECG recordings allows noninvasive localization of atrial reentries during AF and further a physiologically-based rationale for personalized diagnosis and treatment of patients with AF.
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Affiliation(s)
- Felipe Atienza
- Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | | | - María S Guillem
- Bio-ITACA, Universitat Politécnica de Valencia, Valencia, Spain
| | - Omer Berenfeld
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
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Kuklik P, Bidar E, Gharaviri A, Maessen J, Schotten U. Application of phase coherence in assessment of spatial alignment of electrodes during simultaneous endocardial-epicardial direct contact mapping of atrial fibrillation. Europace 2014; 16 Suppl 4:iv135-iv140. [PMID: 25362164 DOI: 10.1093/europace/euu247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Mapping and interpretation of wave conduction patterns recorded during simultaneous mapping of the electrical activity on both endocardial and epicardial surfaces are challenging because of the difficulty of reconstruction of reciprocal alignment of electrodes in space. Here, we suggest a method to overcome this difficulty using a concept of maximized endo-epicardial phase coherence. METHODS AND RESULTS Endo-epicardial mapping was performed in six humans during induced atrial fibrillation (AF) in right atria using two sets of 8 × 8 electrode plaques. For each electrode, mean phase coherence (MPC) with all electrodes on the opposite side of the atrial wall was calculated. Localization error was defined as a distance between the directly opposing electrode and the electrode with the maximal MPC. Overall, there was a linear correlation between MPC and distance between electrodes with R(2) = 0.34. Localization error obtained for electrodes of the plaque in six patients resulted in a mean 2.3 ± 1.9 mm for 25 s electrogram segment length. Eighty-four per cent of the measurements resulted in error smaller than 3.4 mm. The duration of the recording used to compute MPC was negatively correlated with localization error; however, the effect reached plateau for segment durations longer than 15 s. CONCLUSION Application of the concept of maximized endo-epicardial phase coherence to electrograms during AF allows reconstruction of reciprocal alignment of the electrodes on the opposite side of the atrial wall. This approach may be especially useful in settings where the spatial position of endo- and epicardial electrodes for intracardiac mapping cannot otherwise be determined.
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Affiliation(s)
- Pawel Kuklik
- Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands University Heart Center, Department of Cardiology and Electrophysiology, University Hospital Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Elham Bidar
- Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands Department of Cardiothoracic Surgery, Maastricht University Medical Centre, 6202 AZ Maastricht, The Netherlands
| | - Ali Gharaviri
- Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands
| | - Jos Maessen
- Department of Cardiothoracic Surgery, Maastricht University Medical Centre, 6202 AZ Maastricht, The Netherlands
| | - Ulrich Schotten
- Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands
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