65 results found
Ali R, Qureshi N, Liverani S, et al., 2020, Left atrial enhancement correlates with myocardial conduction velocity in patients with persistent atrial fibrillation, Frontiers in Physiology, Vol: 11, ISSN: 1664-042X
Background: Conduction velocity (CV) heterogeneity and myocardial fibrosis both promote re-entry, but the relationship between fibrosis as determined by left atrial (LA) late-gadolinium enhanced cardiac magnetic resonance imaging (LGE-CMRI) and CV remains uncertain.Objective: Although average CV has been shown to correlate with regional LGE-CMRI in patients with persistent AF, we test the hypothesis that a localized relationship exists to underpin LGE-CMRI as a minimally invasive tool to map myocardial conduction properties for risk stratification and treatment guidance.Method: 3D LA electroanatomic maps during LA pacing were acquired from eight patients with persistent AF following electrical cardioversion. Local CVs were computed using triads of concurrently acquired electrograms and were co-registered to allow correlation with LA wall intensities obtained from LGE-CMRI, quantified using normalized intensity (NI) and image intensity ratio (IIR). Association was evaluated using multilevel linear regression.Results: An association between CV and LGE-CMRI intensity was observed at scales comparable to the size of a mapping electrode: −0.11 m/s per unit increase in NI (P < 0.001) and −0.96 m/s per unit increase in IIR (P < 0.001). The magnitude of this change decreased with larger measurement area. Reproducibility of the association was observed with NI, but not with IIR.Conclusion: At clinically relevant spatial scales, comparable to area of a mapping catheter electrode, LGE-CMRI correlates with CV. Measurement scale is important in accurately quantifying the association of CV and LGE-CMRI intensity. Importantly, NI, but not IIR, accounts for changes in the dynamic range of CMRI and enables quantitative reproducibility of the association.
Dvoriashyna M, Repetto R, Tweedy JH, 2019, Oscillatory and steady streaming flow in the anterior chamber of the moving eye, Journal of Fluid Mechanics, Vol: 863, Pages: 904-926, ISSN: 0022-1120
We study the flow induced by eye rotations in the anterior chamber (AC) of the eye, the region between the cornea and the iris. We model the geometry of the AC as a thin domain sitting on the surface of a sphere, and study both the simpler case of a constant-height domain as well as a more realistic AC shape. We model eye rotations as harmonic in time with prescribed frequency ωf and amplitude β , and use lubrication theory to simplify the governing equations. We write the equations in a reference frame moving with the domain and show that fluid motion is governed by three dimensionless parameters: the aspect ratio ϵ of the AC, the angular amplitude β and the Womersley number α . We simplify the equations under the physiologically realistic assumptions that ϵ is small and α large, leading to a linear system that can be decomposed into three harmonics: a dominant frequency component, with frequency ωf , and a steady streaming component and a third component with frequency 2ωf . We solve the problem analytically for the constant-height domain and numerically as the solution of ordinary differential equations in the more realistic geometry. Both the primary flow and the steady streaming are shown to have a highly three-dimensional structure, which has not been highlighted in previous numerical works. We show that the steady streaming is particularly relevant from the clinical point of view, as it induces fluid mixing in the AC. Furthermore, the steady flow component is the dominant mixing mechanism during the night, when the thermal flow induced by temperature variations across the AC is suppressed.
Dvoriashyna M, Pralits JO, Tweedy JH, et al., 2019, Mathematical Models of Aqueous Production, Flow and Drainage, OCULAR FLUID DYNAMICS: ANATOMY, PHYSIOLOGY, IMAGING TECHNIQUES, AND MATHEMATICAL MODELING, Editors: Guidoboni, Harris, Sacco, Publisher: BIRKHAUSER BOSTON, Pages: 227-263, ISBN: 978-3-030-25885-6
Dvoriashyna M, Repetto R, Romano MR, et al., 2018, Aqueous humour flow in the posterior chamber of the eye and its modifications due to pupillary block and iridotomy, MATHEMATICAL MEDICINE AND BIOLOGY-A JOURNAL OF THE IMA, Vol: 35, Pages: 447-467, ISSN: 1477-8599
Roney C, Ng FS, Debney M, et al., 2018, Determinants of new wavefront locations in cholinergic atrial fibrillation, EP-Europace, Vol: 20, Pages: iii3-iii15, ISSN: 1099-5129
AimsAtrial fibrillation (AF) wavefront dynamics are complex and difficult to interpret, contributing to uncertainty about the mechanisms that maintain AF. We aimed to investigate the interplay between rotors, wavelets, and focal sources during fibrillation.Methods and resultsArrhythmia wavefront dynamics were analysed for four optically mapped canine cholinergic AF preparations. A bilayer computer model was tuned to experimental preparations, and varied to have (i) fibrosis in both layers or the epicardium only, (ii) different spatial acetylcholine distributions, (iii) different intrinsic action potential duration between layers, and (iv) varied interlayer connectivity. Phase singularities (PSs) were identified and tracked over time to identify rotational drivers. New focal wavefronts were identified using phase contours. Phase singularity density and new wavefront locations were calculated during AF. There was a single dominant mechanism for sustaining AF in each of the preparations, either a rotational driver or repetitive new focal wavefronts. High-density PS sites existed preferentially around the pulmonary vein junctions. Three of the four preparations exhibited stable preferential sites of new wavefronts. Computational simulations predict that only a small number of connections are functionally important in sustaining AF, with new wavefront locations determined by the interplay between fibrosis distribution, acetylcholine concentration, and heterogeneity in repolarization within layers.ConclusionWe were able to identify preferential sites of new wavefront initiation and rotational activity, in order to determine the mechanisms sustaining AF. Electrical measurements should be interpreted differently according to whether they are endocardial or epicardial recordings.
Natali D, Repetto R, Tweedy JH, et al., 2018, A simple mathematical model of rhegmatogenous retinal detachment, Journal of Fluids and Structures, Vol: 82, Pages: 245-257, ISSN: 0889-9746
The conditions under which rhegmatogenous retinal detachment occurs are poorly understood, which hampers the success rates of surgery. Fluid dynamical effects play a major role, and in this paper we analyse the tendency for the retina to detach further in both the case of a free flap giant retinal tear (GRT) and in the case of a retinal hole (RH). For this purpose we use a mathematical model to investigate the interaction between the fluid flow and the detached retina during saccadic eye movements. The governing equations are solved numerically using a code developed ad hoc. An idealised two-dimensional geometry is used and realistic values of almost all governing parameters are taken from the literature. For the cases of both GRT and a RH we investigate the tendency for the detachment to progress, analysing two different saccadic motions, different lengths of the detached retina, different attachment angles and, in the case of a RH, different hole diameters. In both cases we find that increasing the length of the detached retina increases the tendency for further detachment, while in the RH case, changing its diameter has little or no effect. We also find the existence of an attachment angle that maximises the tendency to detach, and the model indicates that RHs are more prone to detach further than GRTs. In spite of the fact that the model is highly idealised the results agree qualitatively well with the available clinical evidence.
Tweedy JH, Pralits JO, Repetto R, et al., 2018, Flow in the anterior chamber of the eye with an implanted iris-fixated artificial lens, Mathematical Medicine and Biology-a Journal of the IMA, Vol: 35, Pages: 363-385, ISSN: 1477-8599
Flow in the aqueous humour that fills the anterior chamber of the eye occurs in response to the production and drainage of the aqueous humour, and also due to buoyancy effects produced by thermal gradients. Phakic intraocular lenses (pIOLs) are manufactured lenses that are surgically inserted in the eyes of patients to correct refractive errors. Their presence has a dramatic effect on the circulation of the aqueous humour, resulting a very different flow in the anterior chamber, the effects of which have not been extensively investigated. In this article we use a simplified mathematical model to analyse the flow, in order to assess the effect of the implanted lens on the pressure drop required to drive the flow and also on the wall shear stress experienced by the corneal endothelial cells and the cells of the iris. A high pressure drop could result in an increased risk of glaucoma, whilst raised shear stress on the cornea could result in a reduction in the density of endothelial cells there, and on the iris it could result in the detachment of pigment cells, which block the outflow of the eye, also leading to glaucoma. Our results confirm those of previous fully numerical studies, and show that, although the presence of the lens causes significant differences in the flow topology and direction, the typical magnitudes of the shear stress are not significantly changed from the natural case. Our semi-analytical solution allows us to perform a thorough study of the dependence of the results on the controlling parameters and also to understand the basic physical mechanisms underlying flow characteristics.
Argungu M, Tweedy JH, 2017, Microcirculation of blood and interstitial fluid in a poroelastic model of theliver, 6th Bio Conference on Poromechanics 2017, Publisher: ASCE, Pages: 1126-1134
Cirrhosis is a life-threatening condition that represents a leading cause of deathin the western world. In this condition the structure of the liver tissue is altered bythe development of fibrosis, which means it becomes stiffer and its permeability toblood and interstitial flow within the tissue that are vital to its function are reduced.We develop a new mathematical model based on those by Bonfiglio et al (2010) andSiggers et al (2014), which we use to investigate the changes in liver volume, bloodflow and lymphatic uptake, which measures interstitial flow, that occur as the tissuebecomes progressively stiffer. Our results suggest that the typical changes that developduring cirrhosis have a significant effect on the permeability properties, highlightingthe seriousness of this condition.
Roney CH, Cantwell CD, Bayer JD, et al., 2017, Spatial resolution requirements for accurate identification of drivers of atrial fibrillation, Circulation-Arrhythmia and Electrophysiology, Vol: 10, Pages: 1-13, ISSN: 1941-3084
Background—Recent studies have demonstrated conflicting mechanisms underlying atrial fibrillation (AF), with the spatial resolution of data often cited as a potential reason for the disagreement. The purpose of this study was to investigate whether the variation in spatial resolution of mapping may lead to misinterpretation of the underlying mechanism in persistent AF.Methods and Results—Simulations of rotors and focal sources were performed to estimate the minimum number of recording points required to correctly identify the underlying AF mechanism. The effects of different data types (action potentials and unipolar or bipolar electrograms) and rotor stability on resolution requirements were investigated. We also determined the ability of clinically used endocardial catheters to identify AF mechanisms using clinically recorded and simulated data. The spatial resolution required for correct identification of rotors and focal sources is a linear function of spatial wavelength (the distance between wavefronts) of the arrhythmia. Rotor localization errors are larger for electrogram data than for action potential data. Stationary rotors are more reliably identified compared with meandering trajectories, for any given spatial resolution. All clinical high-resolution multipolar catheters are of sufficient resolution to accurately detect and track rotors when placed over the rotor core although the low-resolution basket catheter is prone to false detections and may incorrectly identify rotors that are not present.Conclusions—The spatial resolution of AF data can significantly affect the interpretation of the underlying AF mechanism. Therefore, the interpretation of human AF data must be taken in the context of the spatial resolution of the recordings.
Roney CH, Cantwell CD, Qureshi NA, et al., 2016, Rotor tracking using phase of electrograms recorded during atrial fibrillation, Annals of Biomedical Engineering, Vol: 45, Pages: 910-923, ISSN: 1573-9686
Extracellular electrograms recorded during atrial fibrillation (AF) are challenging to interpret due to the inherent beat-to-beat variability in amplitude and duration. Phase mapping represents these voltage signals in terms of relative position within the cycle, and has been widely applied to action potential and unipolar electrogram data of myocardial fibrillation. To date, however, it has not been applied to bipolar recordings, which are commonly acquired clinically. The purpose of this study is to present a novel algorithm for calculating phase from both unipolar and bipolar electrograms recorded during AF. A sequence of signal filters and processing steps are used to calculate phase from simulated, experimental, and clinical, unipolar and bipolar electrograms. The algorithm is validated against action potential phase using simulated data (trajectory centre error <0.8 mm); between experimental multi-electrode array unipolar and bipolar phase; and for wavefront identification in clinical atrial tachycardia. For clinical AF, similar rotational content (R (2) = 0.79) and propagation maps (median correlation 0.73) were measured using either unipolar or bipolar recordings. The algorithm is robust, uses standard signal processing techniques, and accurately quantifies AF wavefronts and sources. Identifying critical sources, such as rotors, in AF, may allow for more accurate targeting of ablation therapy and improved patient outcomes.
Tweedy JH, Dvoriashyna M, Repetto R, 2016, Aqueous humor flow in the posterior chamber of the eye with iridotomy, Summer Biomechanics, Bioengineering and Biotransport Conference 2016
Schobesberger S, Jonsson P, Buzuk A, et al., 2016, Nanoscale, Voltage-Driven Application of Bioactive Substances onto Cells with Organized Topography, Biophysical Journal, Vol: 110, Pages: 141-146, ISSN: 1542-0086
With scanning ion conductance microscopy (SICM), a noncontact scanning probe technique, it is possible both toobtain information about the surface topography of live cells and to apply molecules onto specific nanoscale structures. Thetechnique is therefore widely used to apply chemical compounds and to study the properties of molecules on the surfaces ofvarious cell types. The heart muscle cells, i.e., the cardiomyocytes, possess a highly elaborate, unique surface topographyincluding transverse-tubule (T-tubule) openings leading into a cell internal system that exclusively harbors many proteins necessaryfor the cell’s physiological function. Here, we applied isoproterenol into these surface openings by changing the appliedvoltage over the SICM nanopipette. To determine the grade of precision of our application we used finite-element simulationsto investigate how the concentration profile varies over the cell surface. We first obtained topography scans of the cardiomyocytesusing SICM and then determined the electrophoretic mobility of isoproterenol in a high ion solution to be 7 10 9 m2/V s.The simulations showed that the delivery to the T-tubule opening is highly confined to the underlying Z-groove, and especially tothe first T-tubule opening, where the concentration is ~6.5 times higher compared to on a flat surface under the same deliverysettings. Delivery to the crest, instead of the T-tubule opening, resulted in a much lower concentration, emphasizing the importanceof topography in agonist delivery. In conclusion, SICM, unlike other techniques, can reliably deliver precise quantities ofcompounds to the T-tubules of cardiomyocytes
Cantwell CD, Roney CH, Ng FS, et al., 2015, Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping, Computers in Biology and Medicine, Vol: 65, Pages: 229-242, ISSN: 0010-4825
Measurements of cardiac conduction velocity provide valuable functional and structural insight into the initiation and perpetuation of cardiac arrhythmias, in both a clinical and laboratory context. The interpretation of activation wavefronts and their propagation can identify mechanistic properties of a broad range of electrophysiological pathologies. However, the sparsity, distribution and uncertainty of recorded data make accurate conduction velocity calculation difficult. A wide range of mathematical approaches have been proposed for addressing this challenge, often targeted towards specific data modalities, species or recording environments. Many of these algorithms require identification of activation times from electrogram recordings which themselves may have complex morphology or low signal-to-noise ratio. This paper surveys algorithms designed for identifying local activation times and computing conduction direction and speed. Their suitability for use in different recording contexts and applications is assessed.
Baksi AJ, Davies JE, Hadjiloizou N, et al., 2015, Attenuation of reflected waves in man during retrograde propagation from femoral artery to proximal aorta, International Journal of Cardiology, Vol: 202, Pages: 441-445, ISSN: 1874-1754
BackgroundWave reflection may be an important influence on blood pressure, but the extent to which reflections undergo attenuation during retrograde propagation has not been studied. We quantified retrograde transmission of a reflected wave created by occlusion of the left femoral artery in man.Methods20 subjects (age 31–83 years; 14 male) underwent invasive measurement of pressure and flow velocity with a sensor-tipped intra-arterial wire at multiple locations distal to the proximal aorta before, during and following occlusion of the left femoral artery by thigh cuff inflation. A numerical model of the circulation was also used to predict reflected wave transmission. Wave reflection was measured as the ratio of backward to forward wave energy (WRI) and the ratio of peak backward to forward pressure (Pb/Pf).ResultsCuff inflation caused a marked reflection which was largest at 5–10 cm from the cuff (change (Δ) in WRI = 0.50 (95% CI 0.38, 0.62); p < 0.001, ΔPb/Pf = 0.23 (0.18–0.29); p < 0.001). The magnitude of the cuff-induced reflection decreased progressively at more proximal locations and was barely discernible at sites > 40 cm from the cuff including in the proximal aorta. Numerical modelling gave similar predictions to those observed experimentally.ConclusionsReflections due to femoral artery occlusion are markedly attenuated by the time they reach the proximal aorta. This is due to impedance mismatches of bifurcations traversed in the backward direction. This degree of attenuation is inconsistent with the idea of a large discrete reflected wave arising from the lower limb and propagating back into the aorta.
Dehbi H-M, Jones S, Sohaib SMA, et al., 2015, A novel curve fitting method for AV optimisation of biventricular pacemakers, PHYSIOLOGICAL MEASUREMENT, Vol: 36, Pages: 1889-1900, ISSN: 0967-3334
Ali RL, Cantwell CD, Qureshi NA, et al., 2015, Automated fiducial point selection for reducing registration error in the co-localisation of left atrium electroanatomic and imaging data., 2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 1989-1992, ISSN: 1557-170X
Registration of electroanatomic surfaces and segmented images for the co-localisation of structural and functional data typically requires the manual selection of fiducial points, which are used to initialise automated surface registration. The identification of equivalent points on geometric features by the human eye is heavily subjective, and error in their selection may lead to distortion of the transformed surface and subsequently limit the accuracy of data co-localisation. We propose that the manual trimming of the pulmonary veins through the region of greatest geometrical curvature, coupled with an automated angle-based fiducial-point selection algorithm, significantly reduces target registration error compared with direct manual selection of fiducial points.
Repetto R, Khongar PD, Pralits JO, et al., 2015, Numerical simulations of flow and mass transport processes in the anterior chamber in the presence of an iris-fixated intraocular lens, Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), Publisher: Association for Research in Vision and Ophthalmology (ARVO), ISSN: 1552-5783
Purpose: In this study we investigated how implantation of iris-fixated intraocular lenses (IOLs) affects aqueous humor flow characteristics and mass transport processes in the anterior chamber. Specifically, we studied changes in the wall shear stress distribution and oxygen/nutrient availability on the cornea, after lens implantation.Methods: We adopted a mathematical model to study aqueous flow and oxygen/nutrient concentration distribution in the anterior chamber in the presence of an iris-fixated IOL. Numerical solutions on idealized but realistic geometries were obtained employing the open source software OpenFOAM. The validity of the numerical results were confirmed by analytical solutions obtained through a simplified model based on the lubrication theory. We considered various mechanisms that generate aqueous flow in the anterior chamber and focused, in particular, on the production/drainage flow and the thermal flow generated by a temperature gradient across the anterior chamber.Results: The model provides a detailed description of the velocity, pressure and concentration distribution in the anterior chamber, both in the presence and absence of the IOL. Results show that changes in fluid pressure after implantation of the IOL are negligible. Wall shear stress distribution and mass transport processes in the anterior chamber are significantly modified by the presence of the IOL. However, the maximum wall shear stress on the cornea does not grow after IOL implantation.Conclusions: The study sheds some light on the changes induced by implantation of an iris-fixated IOL on fluid flow and mass transport in the anterior chamber, an information that would be difficult to obtain without making use of a mathematical model. Results suggest that changes in the wall shear stress, albeit significant, are unlikely to be the cause of the complications associated with the use of iris-fixated IOLs.
Repetto R, Pralits JO, Siggers JH, et al., 2015, Phakic iris-fixated intraocular lens placement in the anterior chamber: effects on aqueous flow., Investigative Ophthalmology & Visual Science, Vol: 56, Pages: 3061-3068, ISSN: 1552-5783
PURPOSE: Phakic intraocular lenses (pIOLs) are used for correcting vision; in this paper we investigate the fluid dynamical effects of an iris-fixated lens in the anterior chamber. In particular, we focus on changes in the wall shear stress (WSS) on the cornea and iris, which could be responsible for endothelial and pigment cell loss, respectively, and also on the possible increase of the intraocular pressure, which is known to correlate with the incidence of secondary glaucoma. METHODS: We use a mathematical model to study fluid flow in the anterior chamber in the presence of a pIOL. The governing equations are solved numerically using the open source software OpenFOAM. We use an idealized standard geometry for the anterior chamber and a realistic geometric description of the pIOL. RESULTS: We consider separately the main mechanisms that produce fluid flow in the anterior chamber. The numerical simulations allow us to obtain a detailed description of the velocity and pressure distribution in the anterior chamber, and indicated that implantation of the pIOL significantly modifies the fluid dynamics in the anterior chamber. However, lens implantation has negligible influence on the intraocular pressure and does not produce a significant increase of the shear stress on the cornea, while the shear stress on the iris, although increased, is not enough to cause detachment of cells. CONCLUSIONS: We conclude that alterations in the fluid dynamics in the anterior chamber as a result of lens implantation are unlikely to be the cause of medical complications associated with its use.
Roney CH, Tzortzis KN, Cantwell CD, et al., 2015, A Technique for Visualising Three-Dimensional Left Atrial Cardiac Activation Data in Two Dimensions with Minimal Distance Distortion, 37th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 7296-7299, ISSN: 1557-170X
Siggers JH, Repetto R, Meskauskas J, 2014, Steady streaming of a viscoelastic fluid within a periodically rotating sphere, Journal of Fluid Mechanics, Vol: 761, Pages: 329-347, ISSN: 1469-7645
Motivated by understanding mass transport processes occurring in the vitreous chamber of the eye, we consider the steady streaming component of the flow generated in a viscoelastic fluid contained within a hollow, rigid sphere performing small-amplitude, periodic, torsional oscillations about an axis passing through its centre. The problem is solved semi-analytically, assuming that the amplitude of the oscillations is small. The paper extends the work by Repetto et al. (J. Fluid Mech., vol. 608, 2008, pp. 71–80), in which the case of a purely viscous fluid was analysed. However, in reality, in young and healthy subjects, the vitreous humour has complex rheological properties, and so here we model it as a viscoelastic fluid. A similar problem was studied by Nikolakis (Eine Theorie für stationäre Drifterscheinungen viskoelastischer Flüssigkeiten, 1992, VDI). In the present model, the steady streaming flow is governed by four dimensionless parameters. We show that, when we account for the viscoelasticity of the fluid, there is a considerably more complex set of possible flow regimes than was found in the purely viscous case, and the flows can be classified into five qualitatively different types. Whereas there was only one circulation cell in each hemisphere in the viscous case, accounting for viscoelasticity it is possible have either one, two or three circulation cells, with different senses of rotation, depending on the parameter values.
Debbaut C, Vierendeels J, Siggers JH, et al., 2014, A 3D porous media liver lobule model: the importance of vascular septa and anisotropic permeability for homogeneous perfusion, Computer Methods in Biomechanics and Biomedical Engineering, Vol: 17, Pages: 1295-1310, ISSN: 1476-8259
The hepatic blood circulation is complex, particularly at the microcirculatory level. Previously, 2D liver lobule models using porous media and a 3D model using real sinusoidal geometries have been developed. We extended these models to investigate the role of vascular septa (VS) and anisotropic permeability. The lobule was modelled as a hexagonal prism (with or without VS) and the tissue was treated as a porous medium (isotropic or anisotropic permeability). Models were solved using computational fluid dynamics. VS inclusion resulted in more spatially homogeneous perfusion. Anisotropic permeability resulted in a larger axial velocity component than isotropic permeability. A parameter study revealed that results are most sensitive to the lobule size and radial pressure drop. Our model provides insight into hepatic microhaemodynamics, and suggests that inclusion of VS in the model leads to perfusion patterns that are likely to reflect physiological reality. The model has potential for applications to unphysiological and pathological conditions.
Roney CH, Cantwell C, Siggers JH, et al., 2014, A Novel Method for Rotor Tracking Using Bipolar Electrogram Phase, Computing in Cardiology (CinC) 2014, Pages: 233-236
Assessing the location and stability of electrical rotors can help target ablation therapy for atrial fibrillation. Rotor cores can be tracked by identifying singularities in the phase of spatially distributed electrical recordings. This is routinely applied to unipolar electrogram and action potential data, but not to bipolar electrogram data, which contains local activation only. We developed and tested a technique to track phase singularities from simulated bipolar data. Bipolar electrogram phase was found to be as effective as action potential and as unipolar electrogram phase for rotor tip detection when using simulated data, suggesting that it may be used clinically as an alternative method to unipolar phase to locate rotor phase singularities in atrial fibrillation.
Roney CH, Cantwell C, Qureshi NA, et al., 2014, An Automated Algorithm for Determining Conduction Velocity, Wavefront Direction and Focal Source Location using a Multipolar Catheter, IEEE Engineering in Medicine and Biology Conference
Determining locations of focal arrhythmia sources and quantifying myocardial conduction velocity (CV) are two major challenges in clinical catheter ablation cases. CV, wavefront direction and focal source location can be estimated from multipolar catheter data, but currently available methods are time-consuming, limited to specific electrode configurations, and can be inaccurate. We developed automated algorithms to rapidly identify CV from multipolar catheter data with any arrangement of electrodes, whilst providing estimates of wavefront direction and focal source position, which can guide the catheter towards a focal arrhythmic source. We validated our methods using simulations on realistic human left atrial geometry. We subsequently applied them to clinically-acquired intracardiac electrogram data, where CV and wavefront direction were accurately determined in all cases, whilst focal source locations were correctly identified in 2/3 cases. Our novel automated algorithms can potentially be used to guide ablation of focal arrhythmias in real-time in cardiac catheter laboratories.
Park CM, Korolkova O, Davies JE, et al., 2014, Arterial pressure: agreement between a brachial cuff-based device and radial tonometry, JOURNAL OF HYPERTENSION, Vol: 32, Pages: 865-872, ISSN: 0263-6352
Siggers JH, Leungchavaphongse K, Ho CH, et al., 2014, Mathematical model of blood and interstitial flow and lymph production in the liver, BIOMECHANICS AND MODELING IN MECHANOBIOLOGY, Vol: 13, Pages: 363-378, ISSN: 1617-7959
Ali RL, Cantwell CD, Roney CH, et al., 2014, A novel method for quantifying localised correlation of late-gadolinium intensity with conduction velocity, Computing in Cardiology (CinC) 2014, Pages: 193-196
Patient-specific computer models of the human atria have the potential to aid clinical intervention in the treatment of cardiac arrhythmias. However, quantifying and integrating the heterogeneous qualities of the myocardium through imaging is particularly challenging due to the unknown relationship between voxel intensity and tissue conductivities. We establish a method to determine the relationship between local conduction velocity and scar density, extracted through the analysis of late-gadolinium enhanced magnetic resonance imaging data.
Setchi A, Mestel AJ, Siggers JH, et al., 2013, Mathematical model of flow through the patent ductus arteriosus, JOURNAL OF MATHEMATICAL BIOLOGY, Vol: 67, Pages: 1487-1506, ISSN: 0303-6812
Setchi A, Mestel AJ, Parker KH, et al., 2013, Low-Reynolds-number flow through two-dimensional shunts, JOURNAL OF FLUID MECHANICS, Vol: 723, Pages: 21-39, ISSN: 0022-1120
Bonfiglio A, Repetto R, Siggers JH, et al., 2013, Investigation of the motion of a viscous fluid in the vitreous cavity induced by eye rotations and implications for drug delivery, PHYSICS IN MEDICINE AND BIOLOGY, Vol: 58, Pages: 1969-1982, ISSN: 0031-9155
Putra NK, Dickinson RJ, Siggers JH, 2013, Image Processing as the Validation Method of Droplet Dispersion Modeling Process, 3rd International Conference on Instrumentation, Communications, Information Technology, and Biomedical Engineering (ICICI-BME), Publisher: IEEE, Pages: 242-245, ISSN: 2158-0456
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