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1. Evaluation of an Open-Source Pipeline to Create Patient-Specific Left Atrial Models: A Reproducibility Study

Author

Solis-Lemus, Jose Alonso, Baptiste, Tiffany, Barrows, Rosie, Sillett, Charles, Gharaviri, Ali, Raffaele, Giulia, Razeghi, Orod, Strocchi, Marina, Sim, Iain, Kotadia, Irum, Bodagh, Neil, O'Hare, Daniel, O'Neill, Mark, Williams, Steven E, Roney, Caroline, and Niederer, Steven

Subjects
Physics - Medical Physics, Computer Science - Computational Engineering, Finance, and Science
Abstract

We present an open-source software pipeline to create patient-specific left atrial (LA) models with fibre orientations and a fibrosis map, suitable for electrophysiology simulations. The semi-automatic pipeline takes as input a contrast enhanced magnetic resonance angiogram, and a late gadolinium enhanced (LGE) contrast magnetic resonance (CMR). Five operators were allocated 20 cases each from a set of 50 CMR datasets to create a total of 100 models to evaluate inter/intra-operator variability. Each output model consisted of (1) a labelled surface mesh open at the pulmonary veins (PV) and mitral valve (MV), (2) fibre orientations mapped from a diffusion tensor MRI human atlas, (3) fibrosis map from the LGE-CMR scan, and (4) simulation of local activation time (LAT) and phase singularity (PS) mapping. We evaluated reproducibility in our pipeline by comparing agreement in shape of the output meshes, fibrosis distribution in the LA body, and fibre orientations; simulations outputs were evaluated comparing total activation times of LAT maps, mean conduction velocity (CV), and structural similarity index measure (SSIM) of PS maps. Our workflow allows a single model to be created in 16.72 +/- 12.25 minutes. Results in this abstract are reported as inter/intra. Shape only differed noticeably with users' selection of the MV and the length of the PV from the ostia to the distal end; fibrosis agreement (0.91/0.99 ICC) and fibre orientation agreement (60.63/71.77 %) were high. LAT maps showed good agreement, the median of the absolute difference of the total activation times was 2.02ms/1.37ms. The average of the mean CV difference was -4.04mm/s / 2.1mm/s. PS maps showed a moderately good agreement with SSIM of 0.648/0.608. Although we found notable differences in the models due to user input, our tests show that operator variability was comparable to that of image resolution or fibre estimation., Comment: 17 pages, 7 figures, submitted for review at Journal of Computers in Biology and Medicine (in press)

Published
2023

2. Global Sensitivity Analysis of Four Chamber Heart Hemodynamics Using Surrogate Models

Author

Karabelas, Elias, Longobardi, Stefano, Fuchsberger, Jana, Razeghi, Orod, Rodero, Cristobal, Strocchi, Marina, Rajani, Ronak, Haase, Gundolf, Plank, Gernot, and Niederer, Steven

Subjects
Physics - Fluid Dynamics, Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Emerging Technologies, Mathematics - Numerical Analysis, G.1.8, J.3, I.2.m
Abstract

Computational Fluid Dynamics (CFD) is used to assist in designing artificial valves and planning procedures, focusing on local flow features. However, assessing the impact on overall cardiovascular function or predicting longer-term outcomes may require more comprehensive whole heart CFD models. Fitting such models to patient data requires numerous computationally expensive simulations, and depends on specific clinical measurements to constrain model parameters, hampering clinical adoption. Surrogate models can help to accelerate the fitting process while accounting for the added uncertainty. We create a validated patient-specific four-chamber heart CFD model based on the Navier-Stokes-Brinkman (NSB) equations and test Gaussian Process Emulators (GPEs) as a surrogate model for performing a variance-based global sensitivity analysis (GSA). GSA identified preload as the dominant driver of flow in both the right and left side of the heart, respectively. Left-right differences were seen in terms of vascular outflow resistances, with pulmonary artery resistance having a much larger impact on flow than aortic resistance. Our results suggest that GPEs can be used to identify parameters in personalized whole heart CFD models, and highlight the importance of accurate preload measurements., Comment: 8 pages plus 15 pages supplement, 6 figures, 3 tables, submitted to IEEE Transactions on Biomedical Engineering

Published
2021
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3. Discriminative Dimension Reduction based on Mutual Information

Author

Razeghi, Orod and Qiu, Guoping

Subjects
Computer Science - Computer Vision and Pattern Recognition
Abstract

The "curse of dimensionality" is a well-known problem in pattern recognition. A widely used approach to tackling the problem is a group of subspace methods, where the original features are projected onto a new space. The lower dimensional subspace is then used to approximate the original features for classification. However, most subspace methods were not originally developed for classification. We believe that direct adoption of these subspace methods for pattern classification should not be considered best practice. In this paper, we present a new information theory based algorithm for selecting subspaces, which can always result in superior performance over conventional methods. This paper makes the following main contributions: i) it improves a common practice widely used by practitioners in the field of pattern recognition, ii) it develops an information theory based technique for systematically selecting the subspaces that are discriminative and therefore are suitable for pattern recognition/classification purposes, iii) it presents extensive experimental results on a variety of computer vision and pattern recognition tasks to illustrate that the subspaces selected based on maximum mutual information criterion will always enhance performance regardless of the classification techniques used.

Published
2019

4. Object Recognition with Human in the Loop Intelligent Frameworks

Author

Razeghi, Orod and Qiu, Guoping

Subjects
Computer Science - Computer Vision and Pattern Recognition
Abstract

Classifiers embedded within human in the loop visual object recognition frameworks commonly utilise two sources of information: one derived directly from the imagery data of an object, and the other obtained interactively from user interactions. These computer vision frameworks exploit human high-level cognitive power to tackle particularly difficult visual object recognition tasks. In this paper, we present innovative techniques to combine the two sources of information intelligently for the purpose of improving recognition accuracy. We firstly employ standard algorithms to build two classifiers for the two sources independently, and subsequently fuse the outputs from these classifiers to make a conclusive decision. The two fusion techniques proposed are: i) a modified naive Bayes algorithm that adaptively selects an individual classifier's output or combines both to produce a definite answer, and ii) a neural network based algorithm which feeds the outputs of the two classifiers to a 4-layer feedforward network to generate a final output. We present extensive experimental results on 4 challenging visual recognition tasks to illustrate that the new intelligent techniques consistently outperform traditional approaches to fusing the two sources of information.

Published
2019

5. A three-dimensional left atrial motion estimation from retrospective gated computed tomography: application in heart failure patients with atrial fibrillation

Author

Sillett, Charles, primary, Razeghi, Orod, additional, Lee, Angela W. C., additional, Solis Lemus, Jose Alonso, additional, Roney, Caroline, additional, Mannina, Carlo, additional, de Vere, Felicity, additional, Ananthan, Kiruthika, additional, Ennis, Daniel B., additional, Haberland, Ulrike, additional, Xu, Hao, additional, Young, Alistair, additional, Rinaldi, Christopher A., additional, Rajani, Ronak, additional, and Niederer, Steven A., additional

Published
2024
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7. Comprehensive use of cardiac computed tomography to guide left ventricular lead placement in cardiac resynchronization therapy

Author

Behar, Jonathan M, Rajani, Ronak, Pourmorteza, Amir, Preston, Rebecca, Razeghi, Orod, Niederer, Steve, Adhya, Shaumik, Claridge, Simon, Jackson, Tom, Sieniewicz, Ben, Gould, Justin, Carr-White, Gerry, Razavi, Reza, McVeigh, Elliot, and Rinaldi, Christopher Aldo

Subjects
Biomedical and Clinical Sciences, Clinical Sciences, Cardiovascular, Heart Disease, Bioengineering, Biomedical Imaging, Heart Disease - Coronary Heart Disease, Evaluation of treatments and therapeutic interventions, 6.3 Medical devices, Aged, Cardiac Resynchronization Therapy, Electrocardiography, Female, Follow-Up Studies, Heart Failure, Heart Ventricles, Humans, Male, Predictive Value of Tests, Reproducibility of Results, Time Factors, Tomography, X-Ray Computed, Ventricular Function, Left, Ventricular Remodeling, Cardiac computed tomography, Cardiac resynchronization therapy, CT guided intervention, Dyssynchrony, Myocardial fibrosis, Biomedical Engineering, Cardiorespiratory Medicine and Haematology, Cardiovascular System & Hematology, Cardiovascular medicine and haematology
Abstract

BackgroundOptimal lead positioning is an important determinant of cardiac resynchronization therapy (CRT) response.ObjectiveThe purpose of this study was to evaluate cardiac computed tomography (CT) selection of the optimal epicardial vein for left ventricular (LV) lead placement by targeting regions of late mechanical activation and avoiding myocardial scar.MethodsEighteen patients undergoing CRT upgrade with existing pacing systems underwent preimplant electrocardiogram-gated cardiac CT to assess wall thickness, hypoperfusion, late mechanical activation, and regions of myocardial scar by the derivation of the stretch quantifier for endocardial engraved zones (SQUEEZ) algorithm. Cardiac venous anatomy was mapped to individualized American Heart Association (AHA) bull's-eye plots to identify the optimal venous target and compared with acute hemodynamic response (AHR) in each coronary venous target using an LV pressure wire.ResultsFifteen data sets were evaluable. CT-SQUEEZ-derived targets produced a similar mean AHR compared with the best achievable AHR (20.4% ± 13.7% vs 24.9% ± 11.1%; P = .36). SQUEEZ-derived guidance produced a positive AHR in 92% of target segments, and pacing in a CT-SQUEEZ target vein produced a greater clinical response rate vs nontarget segments (90% vs 60%).ConclusionPreprocedural CT-SQUEEZ-derived target selection may be a valuable tool to predict the optimal venous site for LV lead placement in patients undergoing CRT upgrade.

Published
2017

10. An investigation of a human in the loop approach to object recognition

Author

Razeghi, Orod

Subjects
006.3, QA 75 Electronic computers. Computer science, TA Engineering (General). Civil engineering (General)
Abstract

For several decades researchers around the globe have been avidly investigating practical solutions to the enduring problem of understanding visual content within an image. One might think of the quest as an effort to emulate human visual system. Despite all the endeavours, the simplest of visual tasks to us humans, such as optical segmentation of objects, remain a significant challenge for machines. In a few occasions where a computer's processing power is adequate to accomplish the task, the issue of public alienation towards autonomous solutions to critical applications remains unresolved. The principal purpose of this thesis is to propose innovative computer vision, machine learning, and pattern recognition techniques that exploit abstract knowledge of human beings in practical models using facile yet effective methodologies. High-level information provided by users in the decision making loop of such interactive systems enhances the efficacy of vision algorithms, whilst simultaneously machines reduce users' labour by filtering results and completing mundane tasks on their behalf. In this thesis, we initially draw a vivid picture of interactive approaches to vision tasks prior to scrutinising relevant aspects of human in the loop methodologies and highlighting their current shortcomings in object recognition applications. Our survey of literature unveils that the difficulty in harnessing users' abstract knowledge is amongst major complications of human in the loop algorithms. We therefore propose two novel methodologies to capture and model such high-level sources of information. One solution builds innovative textual descriptors that are compatible with discriminative classifiers. The other is based on the random naive Bayes algorithm and is suitable for generative classification frameworks. We further investigate the infamous problem of fusing images' low-level and users' high-level information sources. Our next contribution is therefore a novel random forest based human in the loop framework that efficiently fuses visual features of images with user provided information for fast predictions and a superior classification performance. User abstract knowledge in this method is harnessed in shape of user's answers to perceptual questions about images. In contrast to generative Bayesian frameworks, this is a direct discriminative approach that enables information source fusion in the preliminary stages of the prediction process. We subsequently reveal inventive generative frameworks that model each source of information individually and determine the most effective for the purpose of class label prediction. We propose two innovative and intelligent human in the loop fusion algorithms. Our first algorithm is a modified naive Bayes greedy technique, while our second solution is based on a feedforward neural network. Through experiments on a variety of datasets, we show that our novel intelligent fusion methods of information source selection outperform their competitors in tasks of fine-grained visual categorisation. We additionally present methodologies to reduce unnecessary human involvement in mundane tasks by only focusing on cases where their invaluable abstract knowledge is of utter importance. Our proposed algorithm is based on information theory and recent image annotation techniques. It determines the most efficient sequence of information to obtain from humans involved in the decision making loop, in order to minimise their unnecessary engagement in routine tasks. This approach allows them to be concerned with more abstract functions instead. Our experimental results reveal faster achievement of peak performance in contrast to alternative random ranking systems. Our final major contribution in this thesis is a novel remedy for the curse of dimensionality in pattern recognition problems. It is theoretically based on mutual information and Fano's inequality. Our approach separates the most discriminative descriptors and has the capability to enhance the accuracy of classification algorithms. The process of selecting a subset of relevant features is vital for designing robust human in the loop vision models. Our selection techniques eliminate redundant and irrelevant visual and textual features, and therefore its influence on improvement of various human in the loop algorithms proves to be fundamental in our experiments.

Published
2015

14. Improved co-registration of ex-vivo and in-vivo cardiovascular magnetic resonance images using heart-specific flexible 3D printed acrylic scaffold combined with non-rigid registration

Author

Whitaker, John, Neji, Radhouene, Byrne, Nicholas, Puyol-Antón, Esther, Mukherjee, Rahul K., Williams, Steven E., Chubb, Henry, O’Neill, Louisa, Razeghi, Orod, Connolly, Adam, Rhode, Kawal, Niederer, Steven, King, Andrew, Tschabrunn, Cory, Anter, Elad, Nezafat, Reza, Bishop, Martin J., O’Neill, Mark, Razavi, Reza, and Roujol, Sébastien

Published
2019
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18. Right atrial function and fibrosis in relation to successful atrial fibrillation ablation.

Author

Hopman, Luuk H G A, Visch, Julia E, Bhagirath, Pranav, Laan, Anja M van der, Mulder, Mark J, Razeghi, Orod, Kemme, Michiel J B, Niederer, Steven A, Allaart, Cornelis P, and Götte, Marco J W

Subjects
AMBULATORY electrocardiography, ATRIAL fibrillation, FIBROSIS, MAGNETIC resonance imaging, CARDIOVASCULAR system, DISEASE relapse, ABLATION techniques
Abstract

Aims Bi-atrial remodelling in patients with atrial fibrillation (AF) is rarely assessed and data on the presence of right atrial (RA) fibrosis, the relationship between RA and left atrial (LA) fibrosis, and possible association of RA remodelling with AF recurrence after ablation in patients with AF is limited. Methods and results A total of 110 patients with AF undergoing initial pulmonary vein isolation (PVI) were included in the present study. All patients were in sinus rhythm during cardiac magnetic resonance (CMR) imaging performed prior to ablation. LA and RA volumes and function (volumetric and feature tracking strain) were derived from cine CMR images. The extent of LA and RA fibrosis was assessed from 3D late gadolinium enhancement images. AF recurrence was followed up for 12 months after PVI using either 12-lead electrocardiograms or Holter monitoring. Arrhythmia recurrence was observed in 39 patients (36%) after the 90-day blanking period, occurring at a median of 181 (interquartile range: 122–286) days. RA remodelling parameters were not significantly different between patients with and without AF recurrence after ablation, whereas LA remodelling parameters were different (volume, emptying fraction, and strain indices). LA fibrosis had a strong correlation with RA fibrosis (r = 0.88, P < 0.001). Both LA and RA fibrosis were not different between patients with and without AF recurrence. Conclusions This study shows that RA remodelling parameters were not predictive of AF recurrence after AF ablation. Bi-atrial fibrotic remodelling is present in patients with AF and moreover, the amount of LA fibrosis had a strong correlation with the amount of RA fibrosis. [ABSTRACT FROM AUTHOR]

Published
2023
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19. CArdiac MagnEtic resonance assessment of bi-Atrial fibrosis in secundum atrial septal defects patients: CAMERA-ASD study

Author

O’Neill, Louisa, primary, Sim, Iain, additional, O’Hare, Daniel, additional, Whitaker, John, additional, Mukherjee, Rahul K, additional, Razeghi, Orod, additional, Niederer, Steven, additional, Wright, Matthew, additional, Chiribiri, Amedeo, additional, Frigiola, Alessandra, additional, O’Neill, Mark D, additional, and Williams, Steven E, additional

Published
2021
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20. Pulmonary vein encirclement using an Ablation Index-guided point-by-point workflow: cardiovascular magnetic resonance assessment of left atrial scar formation

Author

O’Neill, Louisa, Karim, Rashed, Mukherjee, Rahul K, Whitaker, John, Sim, Iain, Harrison, James, Razeghi, Orod, Niederer, Steven, Ismail, Tevfik, Wright, Matthew, O’Neill, Mark D, and Williams, Steven E

Subjects
Male, Ablation Index, Cardiac-Gated Imaging Techniques, Contrast Media, Middle Aged, Pulmonary vein isolation, Point-by-point ablation, Ablation for Atrial Fibrillation, Workflow, Cicatrix, Clinical Research, Pulmonary Veins, Atrial Fibrillation, Catheter Ablation, Organometallic Compounds, Humans, Female, Atrial ablation scar, Cardiac magnetic resonance imaging, Magnetic Resonance Angiography
Abstract

Aims A point-by-point workflow for pulmonary vein isolation (PVI) targeting pre-defined Ablation Index values (a composite of contact force, time, and power) and minimizing interlesion distance may optimize the creation of contiguous ablation lesions whilst minimizing scar formation. We aimed to compare ablation scar formation in patients undergoing PVI using this workflow to patients undergoing a continuous catheter drag workflow. Methods and results Post-ablation cardiovascular magnetic resonance imaging was performed in patients undergoing 1st-time PVI using a parameter-guided point-by-point workflow (n = 26). Total left atrial scar burden and the width and continuity of the pulmonary vein encirclement were determined on analysis of atrial late gadolinium enhancement sequences. Comparison was made with a cohort of patients (n = 20) undergoing PVI using continuous drag lesions. Mean post-ablation scar burden and scar width were significantly lower in the point-by-point group than in the control group (6.6 ± 6.8% vs. 9.6 ± 5.0%, P = 0.03 and 7.9 ± 3.6 mm vs. 10.7 ± 2.3 mm, P = 0.003). More complete bilateral pulmonary vein encirclements were seen in the point-by-point group (P = 0.038). All patients achieved acute PVI. Conclusion Pulmonary vein isolation using a point-by-point workflow is feasible and results in a lower scar burden and scar width with more complete pulmonary vein encirclements than a conventional drag lesion approach.

Published
2019

21. CArdiac MagnEtic resonance assessment of bi-Atrial fibrosis in secundum atrial septal defects patients: CAMERA-ASD study.

Author

O'Neill, Louisa, Sim, Iain, O'Hare, Daniel, Whitaker, John, Mukherjee, Rahul K, Razeghi, Orod, Niederer, Steven, Wright, Matthew, Chiribiri, Amedeo, Frigiola, Alessandra, O'Neill, Mark D, and Williams, Steven E

Subjects
ATRIAL arrhythmias, HEART septum, FIBROSIS, MAGNETIC resonance imaging, CONGENITAL heart disease, ATRIAL septal defects, RECEIVER operating characteristic curves, SENSITIVITY & specificity (Statistics), RESEARCH bias, LONGITUDINAL method
Abstract

Aims Atrial septal defects (ASD) are associated with atrial arrhythmias, but the arrhythmia substrate in these patients is poorly defined. We hypothesized that bi-atrial fibrosis is present and that right atrial fibrosis is associated with atrial arrhythmias in ASD patients. We aimed to evaluate the extent of bi-atrial fibrosis in ASD patients and to investigate the relationships between bi-atrial fibrosis, atrial arrhythmias, shunt fraction, and age. Methods and results Patients with uncorrected secundum ASDs (n  = 36; 50.4 ± 13.6 years) underwent cardiac magnetic resonance imaging with atrial late gadolinium enhancement. Comparison was made to non-congenital heart disease patients (n  = 36; 60.3 ± 10.5 years) with paroxysmal atrial fibrillation (AF). Cardiac magnetic resonance parameters associated with atrial arrhythmias were identified and the relationship between bi-atrial structure, age, and shunt fraction studied. Bi-atrial fibrosis burden was greater in ASD patients than paroxysmal AF patients (20.7 ± 14% vs. 10.1 ± 8.6% and 14.8 ± 8.5% vs. 8.6 ± 6.1% for right and left atria respectively, P  = 0.001 for both). In ASD patients, right atrial fibrosis burden was greater in those with than without atrial arrhythmias (33.4 ± 18.7% vs. 16.8 ± 10.3%, P  = 0.034). On receiver operating characteristic analysis, a right atrial fibrosis burden of 32% had a 92% specificity and 71% sensitivity for predicting the presence of atrial arrhythmias. Neither age nor shunt fraction was associated with bi-atrial fibrosis burden. Conclusion Bi-atrial fibrosis burden is greater in ASD patients than non-congenital heart disease patients with paroxysmal AF. Right atrial fibrosis is associated with the presence of atrial arrhythmias in ASD patients. These findings highlight the importance of right atrial fibrosis to atrial arrhythmogenesis in ASD patients. [ABSTRACT FROM AUTHOR]

Published
2022
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22. PLoS One / A publicly available virtual cohort of four-chamber heart meshes for cardiac electro-mechanics simulations

Author

Strocchi, Marina, Augustin, Christoph M., Gsell, Matthias A. F., Karabelas, Elias, Neic, Aurel, Gillette, Karli, Razeghi, Orod, Prassl, Anton J., Vigmond, Edward J., Behar, Jonathan M., Gould, Justin, Sidhu, Baldeep, Rinaldi, Christopher A., Bishop, Martin J., Plank, Gernot, Niederer, Steven A., Strocchi, Marina, Augustin, Christoph M., Gsell, Matthias A. F., Karabelas, Elias, Neic, Aurel, Gillette, Karli, Razeghi, Orod, Prassl, Anton J., Vigmond, Edward J., Behar, Jonathan M., Gould, Justin, Sidhu, Baldeep, Rinaldi, Christopher A., Bishop, Martin J., Plank, Gernot, and Niederer, Steven A.

Abstract

Computational models of the heart are increasingly being used in the development of devices, patient diagnosis and therapy guidance. While software techniques have been developed for simulating single hearts, there remain significant challenges in simulating cohorts of virtual hearts from multiple patients. To facilitate the development of new simulation and model analysis techniques by groups without direct access to medical data, image analysis techniques and meshing tools, we have created the first publicly available virtual cohort of twenty-four four-chamber hearts. Our cohort was built from heart failure patients, age 67±14 years. We segmented four-chamber heart geometries from end-diastolic (ED) CT images and generated linear tetrahedral meshes with an average edge length of 1.1±0.2mm. Ventricular fibres were added in the ventricles with a rule-based method with an orientation of -60° and 80° at the epicardium and endocardium, respectively. We additionally refined the meshes to an average edge length of 0.39±0.10mm to show that all given meshes can be resampled to achieve an arbitrary desired resolution. We ran simulations for ventricular electrical activation and free mechanical contraction on all 1.1mm-resolution meshes to ensure that our meshes are suitable for electro-mechanical simulations. Simulations for electrical activation resulted in a total activation time of 149±16ms. Free mechanical contractions gave an average left ventricular (LV) and right ventricular (RV) ejection fraction (EF) of 35±1% and 30±2%, respectively, and a LV and RV stroke volume (SV) of 95±28mL and 65±11mL, respectively. By making the cohort publicly available, we hope to facilitate large cohort computational studies and to promote the development of cardiac computational electro-mechanics for clinical applications., Version of record

Published
2020
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23. Standardised computed tomographic assessment of left atrial morphology and tissue thickness in humans

Author

Whitaker, John, primary, Karády, Júlia, additional, Karim, Rashed, additional, Tobon-Gomez, Catalina, additional, Fastl, Thomas, additional, Razeghi, Orod, additional, O'Neill, Louisa, additional, Decroocq, Marie, additional, Williams, Steven, additional, Corrado, Cesare, additional, Mukherjee, Rahul K., additional, Sim, Iain, additional, O'Hare, Daniel, additional, Kotadia, Irum, additional, Kolossváry, Márton, additional, Merkely, Bela, additional, Littvay, Levente, additional, Tarnoki, Adam D., additional, Tarnoki, David L., additional, Voros, Szilard, additional, Razavi, Reza, additional, O'Neill, Mark, additional, Rajani, Ronak, additional, Maurovich Horvat, Pál, additional, and Niederer, Steven, additional

Published
2021
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24. In silico Comparison of Left Atrial Ablation Techniques That Target the Anatomical, Structural, and Electrical Substrates of Atrial Fibrillation

Author

Roney, Caroline H., primary, Beach, Marianne L., additional, Mehta, Arihant M., additional, Sim, Iain, additional, Corrado, Cesare, additional, Bendikas, Rokas, additional, Solis-Lemus, Jose A., additional, Razeghi, Orod, additional, Whitaker, John, additional, O’Neill, Louisa, additional, Plank, Gernot, additional, Vigmond, Edward, additional, Williams, Steven E., additional, O’Neill, Mark D., additional, and Niederer, Steven A., additional

Published
2020
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26. A publicly available virtual cohort of four-chamber heart meshes for cardiac electro-mechanics simulations

Author

Strocchi, Marina, primary, Augustin, Christoph M., additional, Gsell, Matthias A. F., additional, Karabelas, Elias, additional, Neic, Aurel, additional, Gillette, Karli, additional, Razeghi, Orod, additional, Prassl, Anton J., additional, Vigmond, Edward J., additional, Behar, Jonathan M., additional, Gould, Justin, additional, Sidhu, Baldeep, additional, Rinaldi, Christopher A., additional, Bishop, Martin J., additional, Plank, Gernot, additional, and Niederer, Steven A., additional

Published
2020
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27. A Technique for Measuring Anisotropy in Atrial Conduction to Estimate Conduction Velocity and Atrial Fibre Direction

Author

Roney, Caroline H, Whitaker, John, Sim, Iain James Wyness, O'Neill, Louisa Jane, Mukherjee, Rahul Kumar, Razeghi, Orod, Vigmond, Edward, Wright, Matthew, O'Neill, Mark, Williams, Steven E, and Niederer, Steven A

Subjects
Atrial Fibres, Anisotropy, Atrial fibrillation, Fibrosis, Conduction Velocity
Abstract

Cardiac conduction properties exhibit large variability, and affect patient-specific arrhythmia mechanisms. However, it is challenging to clinically measure conduction velocity (CV), anisotropy and fibre direction. Our aim is to develop a technique to estimate conduction anisotropy and fibre direction from clinically available electrical recordings. Methods: We developed and validated automated algorithms for estimating cardiac CV anisotropy, from any distribution of recording locations on the atrial surface. The first algorithm is for elliptical wavefront fitting to a single activation map (method 1), which works well close to the pacing location, but decreases in accuracy further from the pacing location (due to spatial heterogeneity in the conductivity and fibre fields). As such, we developed a second methodology for measuring local conduction anisotropy, using data from two or three activation maps (method 2: ellipse fitting to wavefront propagation velocity vectors from multiple activation maps). Results: Ellipse fitting to CV vectors from two activation maps (method 2) leads to an improved estimation of longitudinal and transverse CV compared to method 1, but fibre direction estimation is still relatively poor. Using three activation maps with method 2 provides accurate estimation, with approximately 70% of atrial fibres estimated within 20 degrees. We applied the technique to clinical activation maps to demonstrate the presence of heterogeneous conduction anisotropy, and then tested the effects of this conduction anisotropy on predicted arrhythmia dynamics using computational simulation. Conclusions: We have developed novel algorithms for calculating CV and measuring the direction dependency of atrial activation to estimate atrial fibre direction, without the need for specialised pacing protocols, using clinically available electrical recordings.

Published
2019

28. A technique for measuring anisotropy in atrial conduction to estimate conduction velocity and atrial fibre direction

Author

RONEY, Caroline, WHITAKER, John, SIM, Iain, O'NEILL, Louisa, MUKHERJEE, Rahul, RAZEGHI, Orod, VIGMOND, Edward, WRIGHT, Matthew, O'NEILL, Mark, WILLIAMS, Steven, NIEDERER, Steven, King‘s College London, Modélisation et calculs pour l'électrophysiologie cardiaque (CARMEN), IHU-LIRYC, Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-IHU-LIRYC, and Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-CHU Bordeaux [Bordeaux]

Subjects
Atrial fibres, [SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, Heart Conduction System, Conduction velocity, Models, Cardiovascular, Humans, Anisotropy, Computer Simulation, [SDV.IB]Life Sciences [q-bio]/Bioengineering, Heart Atria, Fibrosis, Atrial fibrillation, Article
Abstract

BACKGROUND: Cardiac conduction properties exhibit large variability, and affect patient-specific arrhythmia mechanisms. However, it is challenging to clinically measure conduction velocity (CV), anisotropy and fibre direction. Our aim is to develop a technique to estimate conduction anisotropy and fibre direction from clinically available electrical recordings. METHODS: We developed and validated automated algorithms for estimating cardiac CV anisotropy, from any distribution of recording locations on the atrial surface. The first algorithm is for elliptical wavefront fitting to a single activation map (method 1), which works well close to the pacing location, but decreases in accuracy further from the pacing location (due to spatial heterogeneity in the conductivity and fibre fields). As such, we developed a second methodology for measuring local conduction anisotropy, using data from two or three activation maps (method 2: ellipse fitting to wavefront propagation velocity vectors from multiple activation maps). RESULTS: Ellipse fitting to CV vectors from two activation maps (method 2) leads to an improved estimation of longitudinal and transverse CV compared to method 1, but fibre direction estimation is still relatively poor. Using three activation maps with method 2 provides accurate estimation, with approximately [Formula: see text] of atrial fibres estimated within [Formula: see text]. We applied the technique to clinical activation maps to demonstrate the presence of heterogeneous conduction anisotropy, and then tested the effects of this conduction anisotropy on predicted arrhythmia dynamics using computational simulation. CONCLUSIONS: We have developed novel algorithms for calculating CV and measuring the direction dependency of atrial activation to estimate atrial fibre direction, without the need for specialised pacing protocols, using clinically available electrical recordings.

Published
2019

29. Patient-specific simulations predict efficacy of ablation of interatrial connections for treatment of persistent atrial fibrillation

Author

Roney, Caroline H, Williams, Steven E, Cochet, Hubert, Mukherjee, Rahul K, O'Neill, Louisa, Sim, Iain, Whitaker, John, Razeghi, Orod, Klein, George J, Vigmond, Edward J, O'Neill, Mark, and Niederer, Steven A

Subjects
inter-atrial conduction, atrial fibrosis, phase singularity mapping, Atrial fibrillation, ablation therapy, computer modeling
Abstract

AimsTreatments for persistent atrial fibrillation (AF) offer limited efficacy. One potential strategy aims to return the right atrium (RA) to sinus rhythm (SR) by ablating interatrial connections (IAC) to isolate the atria, but there is limited clinical data to evaluate this ablation approach. We aimed to use simulation to evaluate and predict patient-specific suitability for ablation of IAC to treat AF.Methods and resultsPersistent AF was simulated in 12 patient-specific geometries, incorporating electrophysiological heterogeneity and fibres, with IAC at Bachmann’s bundle, the coronary sinus, and fossa ovalis. Simulations were performed to test the effect of left atrial (LA)-to-RA frequency gradient and fibrotic remodelling on IAC ablation efficacy. During AF, we simulated ablation of one, two, or all three IAC, with or without pulmonary vein isolation and determined if this altered or terminated the arrhythmia. For models without structural remodelling, ablating all IAC terminated RA arrhythmia in 83% of cases. Models with the LA-to-RA frequency gradient removed had an increased success rate (100% success). Ablation of IACs is less effective in cases with fibrotic remodelling (interstitial fibrosis 50% success rate; combination remodelling 67%). Mean number of phase singularities in the RA was higher pre-ablation for IAC failure (success 0.6 ± 0.8 vs. failure 3.2 ± 2.5, P ConclusionThis simulation study predicts that IAC ablation is effective in returning the RA to SR for many cases. Patient-specific modelling approaches have the potential to stratify patients prior to ablation by predicting if drivers are located in the LA or RA. We present a platform for predicting efficacy and informing patient selection for speculative treatments.

Published
2018

30. Patient-specific simulations predict efficacy of ablation of interatrial connections for treatment of persistent atrial fibrillation

Author

Roney, Caroline, Williams, Steven, Cochet, Hubert, Mukherjee, Rahul, O'Neill, Louisa, Sim, Iain, Whitaker, John, Razeghi, Orod, Klein, George, Vigmond, Edward, O'Neill, Mark, Niederer, Steven, King‘s College London, IHU-LIRYC, Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux], Western University of Health Sciences, Modélisation et calculs pour l'électrophysiologie cardiaque (CARMEN), Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-IHU-LIRYC, and Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-CHU Bordeaux [Bordeaux]

Subjects
Patient-Specific Modeling, Time Factors, Clinical Decision-Making, Action Potentials, Ablation therapy, Atrial Function, Right, [SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, Heart Rate, Predictive Value of Tests, Humans, Heart Atria, Phase singularity mapping, Patient Selection, Interatrial conduction, Models, Cardiovascular, Atrial Remodeling, Articles, Atrial fibrosis, Fibrosis, Magnetic Resonance Imaging, Atrial fibrillation, Treatment Outcome, Computer modelling, cardiovascular system, Catheter Ablation, [SDV.IB]Life Sciences [q-bio]/Bioengineering, Atrial Function, Left
Abstract

Aims Treatments for persistent atrial fibrillation (AF) offer limited efficacy. One potential strategy aims to return the right atrium (RA) to sinus rhythm (SR) by ablating interatrial connections (IAC) to isolate the atria, but there is limited clinical data to evaluate this ablation approach. We aimed to use simulation to evaluate and predict patient-specific suitability for ablation of IAC to treat AF. Methods and results Persistent AF was simulated in 12 patient-specific geometries, incorporating electrophysiological heterogeneity and fibres, with IAC at Bachmann’s bundle, the coronary sinus, and fossa ovalis. Simulations were performed to test the effect of left atrial (LA)-to-RA frequency gradient and fibrotic remodelling on IAC ablation efficacy. During AF, we simulated ablation of one, two, or all three IAC, with or without pulmonary vein isolation and determined if this altered or terminated the arrhythmia. For models without structural remodelling, ablating all IAC terminated RA arrhythmia in 83% of cases. Models with the LA-to-RA frequency gradient removed had an increased success rate (100% success). Ablation of IACs is less effective in cases with fibrotic remodelling (interstitial fibrosis 50% success rate; combination remodelling 67%). Mean number of phase singularities in the RA was higher pre-ablation for IAC failure (success 0.6 ± 0.8 vs. failure 3.2 ± 2.5, P

Published
2018

31. Reproducibility of Atrial Fibrosis Assessment Using CMR Imaging and an Open Source Platform

Author

Sim, Iain, primary, Razeghi, Orod, additional, Karim, Rashed, additional, Chubb, Henry, additional, Whitaker, John, additional, O’Neill, Louisa, additional, Mukherjee, Rahul K., additional, Roney, Caroline H., additional, Razavi, Reza, additional, Wright, Matthew, additional, O’Neill, Mark, additional, Niederer, Steven, additional, and Williams, Steven E., additional

Published
2019
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32. Emerging role of cardiac computed tomography in heart failure

Author

Aziz, Waqar, primary, Claridge, Simon, additional, Ntalas, Ioannis, additional, Gould, Justin, additional, Vecchi, Adelaide, additional, Razeghi, Orod, additional, Toth, Daniel, additional, Mountney, Peter, additional, Preston, Rebecca, additional, Rinaldi, Christopher A., additional, Razavi, Reza, additional, Niederer, Steven, additional, and Rajani, Ronak, additional

Published
2019
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33. Pulmonary vein encirclement using an Ablation Index-guided point-by-point workflow: cardiovascular magnetic resonance assessment of left atrial scar formation.

Author

O'Neill, Louisa, Karim, Rashed, Mukherjee, Rahul K, Whitaker, John, Sim, Iain, Harrison, James, Razeghi, Orod, Niederer, Steven, Ismail, Tevfik, Wright, Matthew, O'Neill, Mark D, and Williams, Steven E

Abstract

Aims: A point-by-point workflow for pulmonary vein isolation (PVI) targeting pre-defined Ablation Index values (a composite of contact force, time, and power) and minimizing interlesion distance may optimize the creation of contiguous ablation lesions whilst minimizing scar formation. We aimed to compare ablation scar formation in patients undergoing PVI using this workflow to patients undergoing a continuous catheter drag workflow.Methods and Results: Post-ablation cardiovascular magnetic resonance imaging was performed in patients undergoing 1st-time PVI using a parameter-guided point-by-point workflow (n = 26). Total left atrial scar burden and the width and continuity of the pulmonary vein encirclement were determined on analysis of atrial late gadolinium enhancement sequences. Comparison was made with a cohort of patients (n = 20) undergoing PVI using continuous drag lesions. Mean post-ablation scar burden and scar width were significantly lower in the point-by-point group than in the control group (6.6 ± 6.8% vs. 9.6 ± 5.0%, P = 0.03 and 7.9 ± 3.6 mm vs. 10.7 ± 2.3 mm, P = 0.003). More complete bilateral pulmonary vein encirclements were seen in the point-by-point group (P = 0.038). All patients achieved acute PVI.Conclusion: Pulmonary vein isolation using a point-by-point workflow is feasible and results in a lower scar burden and scar width with more complete pulmonary vein encirclements than a conventional drag lesion approach. [ABSTRACT FROM AUTHOR]

Published
2019
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34. An investigation of a human in the loop approach to object recognition

Author

Razeghi, Orod and Razeghi, Orod

Abstract

For several decades researchers around the globe have been avidly investigating practical solutions to the enduring problem of understanding visual content within an image. One might think of the quest as an effort to emulate human visual system. Despite all the endeavours, the simplest of visual tasks to us humans, such as optical segmentation of objects, remain a significant challenge for machines. In a few occasions where a computer's processing power is adequate to accomplish the task, the issue of public alienation towards autonomous solutions to critical applications remains unresolved. The principal purpose of this thesis is to propose innovative computer vision, machine learning, and pattern recognition techniques that exploit abstract knowledge of human beings in practical models using facile yet effective methodologies. High-level information provided by users in the decision making loop of such interactive systems enhances the efficacy of vision algorithms, whilst simultaneously machines reduce users' labour by filtering results and completing mundane tasks on their behalf. In this thesis, we initially draw a vivid picture of interactive approaches to vision tasks prior to scrutinising relevant aspects of human in the loop methodologies and highlighting their current shortcomings in object recognition applications. Our survey of literature unveils that the difficulty in harnessing users' abstract knowledge is amongst major complications of human in the loop algorithms. We therefore propose two novel methodologies to capture and model such high-level sources of information. One solution builds innovative textual descriptors that are compatible with discriminative classifiers. The other is based on the random naive Bayes algorithm and is suitable for generative classification frameworks. We further investigate the infamous problem of fusing images' low-level and users' high-level information sources. Our next contribution is therefore a novel random forest

35. An investigation of a human in the loop approach to object recognition

Author

Razeghi, Orod and Razeghi, Orod

Abstract

For several decades researchers around the globe have been avidly investigating practical solutions to the enduring problem of understanding visual content within an image. One might think of the quest as an effort to emulate human visual system. Despite all the endeavours, the simplest of visual tasks to us humans, such as optical segmentation of objects, remain a significant challenge for machines. In a few occasions where a computer's processing power is adequate to accomplish the task, the issue of public alienation towards autonomous solutions to critical applications remains unresolved. The principal purpose of this thesis is to propose innovative computer vision, machine learning, and pattern recognition techniques that exploit abstract knowledge of human beings in practical models using facile yet effective methodologies. High-level information provided by users in the decision making loop of such interactive systems enhances the efficacy of vision algorithms, whilst simultaneously machines reduce users' labour by filtering results and completing mundane tasks on their behalf. In this thesis, we initially draw a vivid picture of interactive approaches to vision tasks prior to scrutinising relevant aspects of human in the loop methodologies and highlighting their current shortcomings in object recognition applications. Our survey of literature unveils that the difficulty in harnessing users' abstract knowledge is amongst major complications of human in the loop algorithms. We therefore propose two novel methodologies to capture and model such high-level sources of information. One solution builds innovative textual descriptors that are compatible with discriminative classifiers. The other is based on the random naive Bayes algorithm and is suitable for generative classification frameworks. We further investigate the infamous problem of fusing images' low-level and users' high-level information sources. Our next contribution is therefore a novel random forest

36. Right atrial function and fibrosis in relation to successful atrial fibrillation ablation.

Author

Hopman LHGA, Visch JE, Bhagirath P, van der Laan AM, Mulder MJ, Razeghi O, Kemme MJB, Niederer SA, Allaart CP, and Götte MJW

Subjects
Humans, Contrast Media, Atrial Function, Right, Gadolinium, Heart Atria, Fibrosis, Recurrence, Treatment Outcome, Atrial Fibrillation diagnostic imaging, Atrial Fibrillation surgery, Atrial Fibrillation pathology, Catheter Ablation methods
Abstract

Aims: Bi-atrial remodelling in patients with atrial fibrillation (AF) is rarely assessed and data on the presence of right atrial (RA) fibrosis, the relationship between RA and left atrial (LA) fibrosis, and possible association of RA remodelling with AF recurrence after ablation in patients with AF is limited., Methods and Results: A total of 110 patients with AF undergoing initial pulmonary vein isolation (PVI) were included in the present study. All patients were in sinus rhythm during cardiac magnetic resonance (CMR) imaging performed prior to ablation. LA and RA volumes and function (volumetric and feature tracking strain) were derived from cine CMR images. The extent of LA and RA fibrosis was assessed from 3D late gadolinium enhancement images. AF recurrence was followed up for 12 months after PVI using either 12-lead electrocardiograms or Holter monitoring. Arrhythmia recurrence was observed in 39 patients (36%) after the 90-day blanking period, occurring at a median of 181 (interquartile range: 122-286) days. RA remodelling parameters were not significantly different between patients with and without AF recurrence after ablation, whereas LA remodelling parameters were different (volume, emptying fraction, and strain indices). LA fibrosis had a strong correlation with RA fibrosis (r = 0.88, P < 0.001). Both LA and RA fibrosis were not different between patients with and without AF recurrence., Conclusions: This study shows that RA remodelling parameters were not predictive of AF recurrence after AF ablation. Bi-atrial fibrotic remodelling is present in patients with AF and moreover, the amount of LA fibrosis had a strong correlation with the amount of RA fibrosis., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Published
2023
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37. CArdiac MagnEtic resonance assessment of bi-Atrial fibrosis in secundum atrial septal defects patients: CAMERA-ASD study.

Author

O'Neill L, Sim I, O'Hare D, Whitaker J, Mukherjee RK, Razeghi O, Niederer S, Wright M, Chiribiri A, Frigiola A, O'Neill MD, and Williams SE

Subjects
Contrast Media, Fibrosis, Gadolinium, Heart Atria, Humans, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Atrial Fibrillation complications, Heart Septal Defects, Atrial complications, Heart Septal Defects, Atrial diagnostic imaging, Heart Septal Defects, Atrial pathology
Abstract

Aims: Atrial septal defects (ASD) are associated with atrial arrhythmias, but the arrhythmia substrate in these patients is poorly defined. We hypothesized that bi-atrial fibrosis is present and that right atrial fibrosis is associated with atrial arrhythmias in ASD patients. We aimed to evaluate the extent of bi-atrial fibrosis in ASD patients and to investigate the relationships between bi-atrial fibrosis, atrial arrhythmias, shunt fraction, and age., Methods and Results: Patients with uncorrected secundum ASDs (n = 36; 50.4 ± 13.6 years) underwent cardiac magnetic resonance imaging with atrial late gadolinium enhancement. Comparison was made to non-congenital heart disease patients (n = 36; 60.3 ± 10.5 years) with paroxysmal atrial fibrillation (AF). Cardiac magnetic resonance parameters associated with atrial arrhythmias were identified and the relationship between bi-atrial structure, age, and shunt fraction studied. Bi-atrial fibrosis burden was greater in ASD patients than paroxysmal AF patients (20.7 ± 14% vs. 10.1 ± 8.6% and 14.8 ± 8.5% vs. 8.6 ± 6.1% for right and left atria respectively, P = 0.001 for both). In ASD patients, right atrial fibrosis burden was greater in those with than without atrial arrhythmias (33.4 ± 18.7% vs. 16.8 ± 10.3%, P = 0.034). On receiver operating characteristic analysis, a right atrial fibrosis burden of 32% had a 92% specificity and 71% sensitivity for predicting the presence of atrial arrhythmias. Neither age nor shunt fraction was associated with bi-atrial fibrosis burden., Conclusion: Bi-atrial fibrosis burden is greater in ASD patients than non-congenital heart disease patients with paroxysmal AF. Right atrial fibrosis is associated with the presence of atrial arrhythmias in ASD patients. These findings highlight the importance of right atrial fibrosis to atrial arrhythmogenesis in ASD patients., Competing Interests: Conflict of interest: M.O’N. has received research support and honoraria from Biosense Webster and St. Jude Medical. S.E.W. has received research support from Biosense Webster. The remaining authors have nothing to disclose., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Published
2022
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38. Standardised computed tomographic assessment of left atrial morphology and tissue thickness in humans.

Author

Whitaker J, Karády J, Karim R, Tobon-Gomez C, Fastl T, Razeghi O, O'Neill L, Decroocq M, Williams S, Corrado C, Mukherjee RK, Sim I, O'Hare D, Kotadia I, Kolossváry M, Merkely B, Littvay L, Tarnoki AD, Tarnoki DL, Voros S, Razavi R, O'Neill M, Rajani R, Maurovich Horvat P, and Niederer S

Abstract

Aims: Left atrial (LA) remodelling is a common feature of many cardiovascular pathologies and is a sensitive marker of adverse cardiovascular outcomes. The aim of this study was to establish normal ranges for LA parameters derived from coronary computed tomographic angiography (CCTA) imaging using a standardised image processing pipeline to establish normal ranges in a previously described cohort., Methods: CCTA imaging from 193 subjects recruited to the Budapest GLOBAL twin study was analysed. Indexed LA cavity volume (LACV i ), LA surface area (LASA i ), wall thickness and LA tissue volume (LATV i ) were calculated. Wall thickness maps were combined into an atlas. Indexed LA parameters were compared with clinical variables to identify early markers of pathological remodelling., Results: LACV i is similar between sexes (31 ml/m 2 v 30 ml/m 2 ) and increased in hypertension (33 ml/m 2 v 29 ml/m 2 , p = 0.009). LASA i is greater in females than males (47.8 ml/m 2 v 45.8 ml/m 2 male, p = 0.031). Median LAWT was 1.45 mm. LAWT was lowest at the inferior portion of the posterior LA wall (1.14 mm) and greatest in the septum (median = 2.0 mm) (p < 0.001). Conditions known to predispose to the development of AF were not associated with differences in tissue thickness., Conclusions: The reported LACV i , LASA i , LATV i and tissue thickness derived from CCTA may serve as reference values for this age group and clinical characteristics for future studies. Increased LASA i in females in the absence of differences in LACV i or LATV i may indicate differential LA shape changes between the sexes. AF predisposing conditions, other than sex, were not associated with detectable changes in LAWT. Clinical trial registration: http://www.ClinicalTrials.gov/NCT01738828., Competing Interests: The authors report no relationships that could be construed as a conflict of interest., (© 2020 Published by Elsevier B.V.)

Published
2020
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39. Pulmonary vein encirclement using an Ablation Index-guided point-by-point workflow: cardiovascular magnetic resonance assessment of left atrial scar formation.

Author

O'Neill L, Karim R, Mukherjee RK, Whitaker J, Sim I, Harrison J, Razeghi O, Niederer S, Ismail T, Wright M, O'Neill MD, and Williams SE

Subjects
Cardiac-Gated Imaging Techniques, Contrast Media, Female, Humans, Male, Middle Aged, Organometallic Compounds, Workflow, Atrial Fibrillation surgery, Catheter Ablation, Cicatrix diagnostic imaging, Magnetic Resonance Angiography methods, Pulmonary Veins diagnostic imaging, Pulmonary Veins surgery
Abstract

Aims: A point-by-point workflow for pulmonary vein isolation (PVI) targeting pre-defined Ablation Index values (a composite of contact force, time, and power) and minimizing interlesion distance may optimize the creation of contiguous ablation lesions whilst minimizing scar formation. We aimed to compare ablation scar formation in patients undergoing PVI using this workflow to patients undergoing a continuous catheter drag workflow., Methods and Results: Post-ablation cardiovascular magnetic resonance imaging was performed in patients undergoing 1st-time PVI using a parameter-guided point-by-point workflow (n = 26). Total left atrial scar burden and the width and continuity of the pulmonary vein encirclement were determined on analysis of atrial late gadolinium enhancement sequences. Comparison was made with a cohort of patients (n = 20) undergoing PVI using continuous drag lesions. Mean post-ablation scar burden and scar width were significantly lower in the point-by-point group than in the control group (6.6 ± 6.8% vs. 9.6 ± 5.0%, P = 0.03 and 7.9 ± 3.6 mm vs. 10.7 ± 2.3 mm, P = 0.003). More complete bilateral pulmonary vein encirclements were seen in the point-by-point group (P = 0.038). All patients achieved acute PVI., Conclusion: Pulmonary vein isolation using a point-by-point workflow is feasible and results in a lower scar burden and scar width with more complete pulmonary vein encirclements than a conventional drag lesion approach., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Published
2019
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