Publications
487 results found
Sohaib SMA, Wright I, Lim E, et al., 2015, Atrioventricular Optimized Direct His Bundle Pacing Improves Acute Hemodynamic Function in Patients With Heart Failure and PR Interval Prolongation Without Left Bundle Branch Block, JACC: Clinical electrophysiology, Vol: 1, Pages: 582-591, ISSN: 2405-5018
ObjectivesThe purpose of this study was to investigate whether heart failure patients with narrow QRS duration (or right bundle branch block) but with long PR interval gain acute hemodynamic benefit from atrioventricular (AV) optimization. We tested this with biventricular pacing and (to deliver pure AV shortening) direct His bundle pacing.BackgroundBenefits of pacing for heart failure have previously been indicated by acute hemodynamic studies and verified in outcome studies. A new target for pacing in heart failure may be PR interval prolongation, which is associated with 58% higher mortality regardless of QRS duration.MethodsWe enrolled 16 consecutive patients with systolic heart failure, PR interval prolongation (mean, 254 ± 62 ms) and narrow QRS duration (n = 13; mean QRS duration: 119 ± 17 ms) or right bundle branch block (n = 3; mean, QRS duration: 156 ± 18 ms). We successfully delivered temporary direct His bundle pacing in 14 patients and temporary biventricular pacing in 14 participants. We performed AV optimization using invasive systolic blood pressure obtaining parabolic responses (mean R2: 0.90 for His, and 0.85 for biventricular pacing).ResultsThe mean increment in systolic BP compared with intrinsic ventricular conduction was 4.1 mm Hg (95% confidence interval [CI]: +1.9 to +6.2 mm Hg for His and 4.3 mm Hg [95% CI: +2.0 to +6.5 mm Hg] for biventricular pacing. QRS duration lengthened with biventricular pacing (change = +22 ms [95% CI: +18 to +25 ms]) but not with His pacing (change = +0.5 ms [95% CI: −2.6 to +3.6 ms).ConclusionsAV-optimized pacing improves acute hemodynamic function in patients with heart failure and long PR interval without left bundle branch block. That it can be achieved by single-site His pacing shows that its mechanism is AV shortening. The improvement is ∼60% of the effect size previously reported for biventricular pacing in left bundle branch block. Randomized, blinded trials are warranted to tes
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.
Ciaccio EJ, Coromilas J, Ashikaga H, et al., 2015, Reprint of 'Model of unidirectional block formation leading to reentrant ventricular tachycardia in the infarct border zone of postinfarction canine hearts', COMPUTERS IN BIOLOGY AND MEDICINE, Vol: 65, Pages: 256-266, ISSN: 0010-4825
Ng FS, Lyon AR, Shadi IT, et al., 2015, Gap Junctional Uncoupling with Carbenoxolone Slows Conduction and Increases Vulnerability to Ventricular Arrhythmias in Structurally Normal Hearts: An Optical Mapping Study, British Cardiovascular Society Annual Conference 2010, Pages: A5-A6
Ng FS, Lyon AR, Shadi IT, et al., 2015, Modulation of Gap Junctional Coupling as an Anti-Arrhythmic Strategy to Prevent Reperfusion Ventricular Fibrillation, SET for Britain 2010 (House of Commons, UK Parliament)
Tzortzis KN, Roney CH, Qureshi NA, et al., 2015, Influence of left atrial geometry on rotor core trajectories in a model of atrial fibrillation, Computing in Cardiology, Publisher: IEEE, Pages: 481-484, ISSN: 2325-8861
Left atrial anatomy and myocardial architecture areknown to influence rotor initiation and maintenance.However, identifying their relative contribution clinicallyis challenging. The present study aims to investigate insilico the effect of left atrial geometry in isolation onrotor generation and evolution through thespatiotemporal tracking of phase singularities. Aftermeandering for a short period of time, rotors areattracted to specific areas of the chamber where there ishigh curvature, primarily near the base of the left atrialappendage and the junctions of the pulmonary veins. Thissuggests that the left atrial anatomy could play a key rolein the perpetuation of fibrillatory activity.
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.
Dyer BT, Elder JM, Lagarto J, et al., 2015, Application of label-free autofluorescence lifetime in vivo to measure changes in myocardial fibrosis and metabolism in a doxorubicin cardiomyopathy heart failure model, Congress of the European-Society-of-Cardiology (ESC), Publisher: OXFORD UNIV PRESS, Pages: 151-151, ISSN: 0195-668X
Koa-Wing M, Nakagawa H, Luther V, et al., 2015, A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias, International Journal of Cardiology, Vol: 199, Pages: 391-400, ISSN: 1874-1754
BackgroundRipple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage–time relationship, relative to a fiduciary point.ObjectiveWe tested the hypothesis that standard approaches to atrial tachycardia CARTO™ activation maps were inadequate for RM creation and interpretation. From the results, we aimed to develop an algorithm to optimize RMs for future prospective testing on a clinical RM platform.MethodsCARTO-XP™ activation maps from atrial tachycardia ablations were reviewed by two blinded assessors on an off-line RM workstation. Ripple Maps were graded according to a diagnostic confidence scale (Grade I — high confidence with clear pattern of activation through to Grade IV — non-diagnostic). The RM-based diagnoses were corroborated against the clinical diagnoses.Results43 RMs from 14 patients were classified as Grade I (5 [11.5%]); Grade II (17 [39.5%]); Grade III (9 [21%]) and Grade IV (12 [28%]). Causes of low gradings/errors included the following: insufficient chamber point density; window-of-interest < 100% of cycle length (CL); < 95% tachycardia CL mapped; variability of CL and/or unstable fiducial reference marker; and suboptimal bar height and scar settings.ConclusionsA data collection and map interpretation algorithm has been developed to optimize Ripple Maps in atrial tachycardias. This algorithm requires prospective testing on a real-time clinical platform.
Ciaccio EJ, Coromilas J, Ashikaga H, et al., 2015, Model of unidirectional block formation leading to reentrant ventricular tachycardia in the infarct border zone of postinfarction canine hearts., Computers in Biology and Medicine, Vol: 62, Pages: 254-263, ISSN: 0010-4825
BACKGROUND: When the infarct border zone is stimulated prematurely, a unidirectional block line (UBL) can form and lead to double-loop (figure-of-eight) reentrant ventricular tachycardia (VT) with a central isthmus. The isthmus is composed of an entrance, center, and exit. It was hypothesized that for certain stimulus site locations and coupling intervals, the UBL would coincide with the isthmus entrance boundary, where infarct border zone thickness changes from thin-to-thick in the travel direction of the premature stimulus wavefront. METHOD: A quantitative model was developed to describe how thin-to-thick changes in the border zone result in critically convex wavefront curvature leading to conduction block, which is dependent upon coupling interval. The model was tested in 12 retrospectively analyzed postinfarction canine experiments. Electrical activation was mapped for premature stimulation and for the first reentrant VT cycle. The relationship of functional conduction block forming during premature stimulation to functional block during reentrant VT was quantified. RESULTS: For an appropriately placed stimulus, in accord with model predictions: (1) The UBL and reentrant VT isthmus lateral boundaries overlapped (error: 4.8±5.7mm). (2) The UBL leading edge coincided with the distal isthmus where the center-entrance boundary would be expected to occur. (3) The mean coupling interval was 164.6±11.0ms during premature stimulation and 190.7±20.4ms during the first reentrant VT cycle, in accord with model calculations, which resulted in critically convex wavefront curvature with functional conduction block, respectively, at the location of the isthmus entrance boundary and at the lateral isthmus edges. DISCUSSION: Reentrant VT onset following premature stimulation can be explained by the presence of critically convex wavefront curvature and unidirectional block at the isthmus entrance boundary when the premature stimulation interval is sufficientl
Fung E, Järvelin MR, Doshi RN, et al., 2015, Electrocardiographic patch devices and contemporary wireless cardiac monitoring., Frontiers in Physiology, Vol: 6, ISSN: 1664-042X
Cardiac electrophysiologic derangements often coexist with disorders of the circulatory system. Capturing and diagnosing arrhythmias and conduction system disease may lead to a change in diagnosis, clinical management and patient outcomes. Standard 12-lead electrocardiogram (ECG), Holter monitors and event recorders have served as useful diagnostic tools over the last few decades. However, their shortcomings are only recently being addressed by emerging technologies. With advances in device miniaturization and wireless technologies, and changing consumer expectations, wearable "on-body" ECG patch devices have evolved to meet contemporary needs. These devices are unobtrusive and easy to use, leading to increased device wear time and diagnostic yield. While becoming the standard for detecting arrhythmias and conduction system disorders in the outpatient setting where continuous ECG monitoring in the short to medium term (days to weeks) is indicated, these cardiac devices and related digital mobile health technologies are reshaping the clinician-patient interface with important implications for future healthcare delivery.
Dyer BTB, de Jesus Reis Lagarto J, Sikkel M, et al., 2015, Application of label-free autofluorescence lifetime in vivo to measure changes in myocardial fibrosis and metabolism associated with myocardial infarction and heart failure, EUROPEAN JOURNAL OF HEART FAILURE, Vol: 17, Pages: 367-367, ISSN: 1388-9842
Luther V, Jamil-Copley S, Koa-Wing M, et al., 2015, Non-randomised comparison of acute and long-term outcomes of robotic versus manual ventricular tachycardia ablation in a single centre ischemic cohort., Journal of Interventional Cardiac Electrophysiology, Vol: 43, Pages: 175-185, ISSN: 1572-8595
INTRODUCTION: Robotically guided radiofrequency (RF) ablation offers greater catheter stability that may improve lesion depth. We performed a non-randomised comparison of patients undergoing ventricular tachycardia (VT) ablation either manually or robotically using the Hansen Sensei system for recurrent implantable defibrillator (ICD) therapy. METHODS: Patients with infarct-related scar underwent VT ablation using the Hansen system to assess feasibility compared with patients undergoing manual VT ablation during a similar time period. Power delivery during robotic ablation was restricted to 30 W at 60 s. VT inducibility was checked at the end of the procedure. Pre-ablation ICD therapy burdens over 6 months were compared with post-ablation therapy averaged to a 6-month period. RESULTS: Twelve consecutive patients who underwent robotic VT ablation were compared to 12 consecutive patients undergoing a manual ablation. Patient demographics and comorbidities were similar in the two groups. A higher proportion of robotic cases were urgent (9/12 (75 %)) vs. manual (4/12 (33 %)) (p = 0.1). Post-ablation VT stimulation did not induce clinical VT in 11/12 (92 %) in each group. There were no peri-procedural complications related to ablation delivery. Patients were followed up for approximately 2 years. Averaged over 6 months, robotic ICD therapy burdens fell from 32 (5-400) events to 2.5 (0-11) (p = 0.015). Therapy burden fell from 14 (10-25) to 1 (0-5) (p = 0.023) in the manual group. There was no difference in long-term outcome (p = 0.60) and mortality (4/12 (33 %), p = 1.0). CONCLUSION: Robotically guided VT ablation is both feasible and safe when compared to manual ablation with good acute and long-term outcomes.
Sohaib SM, Kyriacou A, Jones S, et al., 2015, Evidence that conflict regarding size of haemodynamic response to interventricular delay optimization of cardiac resynchronization therapy may arise from differences in how atrioventricular delay is kept constant., Europace, Vol: 17, ISSN: 1532-2092
AIMS: Whether adjusting interventricular (VV) delay changes haemodynamic efficacy of cardiac resynchronization therapy (CRT) is controversial, with conflicting results. This study addresses whether the convention for keeping atrioventricular (AV) delay constant during VV optimization might explain these conflicts. METHOD AND RESULTS: Twenty-two patients in sinus rhythm with existing CRT underwent VV optimization using non-invasive systolic blood pressure. Interventricular optimization was performed with four methods for keeping the AV delay constant: (i) atrium and left ventricle delay kept constant, (ii) atrium and right ventricle delay kept constant, (iii) time to the first-activated ventricle kept constant, and (iv) time to the second-activated ventricle kept constant. In 11 patients this was performed with AV delay of 120 ms, and in 11 at AV optimum. At AV 120 ms, time to the first ventricular lead (left or right) was the overwhelming determinant of haemodynamics (13.75 mmHg at ±80 ms, P < 0.001) with no significant effect of time to second lead (0.47 mmHg, P = 0.50), P < 0.001 for difference. At AV optimum, time to first ventricular lead again had a larger effect (5.03 mmHg, P < 0.001) than time to second (2.92 mmHg, P = 0.001), P = 0.02 for difference. CONCLUSION: Time to first ventricular activation is the overwhelming determinant of circulatory function, regardless of whether this is the left or right ventricular lead. If this is kept constant, the effect of changing time to the second ventricle is small or nil, and is not beneficial. In practice, it may be advisable to leave VV delay at zero. Specifying how AV delay is kept fixed might make future VV delay research more enlightening.
Tondato F, Zeng H, Goodchild T, et al., 2015, Autologous Dermal Fibroblast Injections Slow Atrioventricular Conduction and Ventricular Rate in Atrial Fibrillation in Swine, Circulation-Arrhythmia and Electrophysiology, Vol: 8, Pages: 439-446, ISSN: 1941-3149
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- Citations: 2
Finegold J, Bordachar P, Kyriacou A, et al., 2015, Atrioventricular delay optimization of cardiac resynchronisation therapy: Comparison of non-invasive blood pressure with invasive haemodynamic measures, INTERNATIONAL JOURNAL OF CARDIOLOGY, Vol: 180, Pages: 221-222, ISSN: 0167-5273
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- Citations: 7
Jamil-Copley S, Vergara P, Carbucicchio C, et al., 2015, Application of Ripple Mapping to Visualize Slow Conduction Channels Within the Infarct-Related Left Ventricular Scar, CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 8, Pages: 76-U110, ISSN: 1941-3149
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- Citations: 33
Kirubakaran S, Chowdhury RA, Hall MCS, et al., 2015, Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model, HEART RHYTHM, Vol: 12, Pages: 397-408, ISSN: 1547-5271
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- Citations: 10
Christensen K, Manani KA, Peters NS, 2015, Simple model for identifying critical regions in atrial fibrillation, Physical Review Letters, Vol: 114, ISSN: 0031-9007
Atrial fibrillation (AF) is the most common abnormal heart rhythm and the single biggest cause of stroke. Ablation, destroying regions of the atria, is applied largely empirically and can be curative but with a disappointing clinical success rate. We design a simple model of activation wave front propagation on an anisotropic structure mimicking the branching network of heart muscle cells. This integration of phenomenological dynamics and pertinent structure shows how AF emerges spontaneously when the transverse cell-to-cell coupling decreases, as occurs with age, beyond a threshold value. We identify critical regions responsible for the initiation and maintenance of AF, the ablation of which terminates AF. The simplicity of the model allows us to calculate analytically the risk of arrhythmia and express the threshold value of transversal cell-to-cell coupling as a function of the model parameters. This threshold value decreases with increasing refractory period by reducing the number of critical regions which can initiate and sustain microreentrant circuits. These biologically testable predictions might inform ablation therapies and arrhythmic risk assessment.
Lagarto J, Dyer BT, Talbot C, et al., 2015, Application of time-resolved autofluorescence to label-free in vivo optical mapping of changes in tissue matrix and metabolism associated with myocardial infarction and heart failure, Biomedical Optics Express, Vol: 6, Pages: 324-346, ISSN: 2156-7085
We investigate the potential of an instrument combining timeresolvedspectrofluorometry and diffuse reflectance spectroscopy tomeasure structural and metabolic changes in cardiac tissue in vivo in a 16week post-myocardial infarction heart failure model in rats. In the scarregion, we observed changes in the fluorescence signal that can beexplained by increased collagen content, which is in good agreement withhistology. In areas remote from the scar tissue, we measured changes in thefluorescence signal (p < 0.001) that cannot be explained by differences incollagen content and we attribute this to altered metabolism within themyocardium. A linear discriminant analysis algorithm was applied to themeasurements to predict the tissue disease state. When we combine allmeasurements, our results reveal high diagnostic accuracy in the infarctedarea (100%) and border zone (94.44%) as well as in remote regions fromthe scar (> 77%). Overall, our results demonstrate the potential of ourinstrument to characterize structural and metabolic changes in a failing heartin vivo without using exogenous labels.
Zaman JAB, Peters NS, Narayan SM, 2015, Rotor mapping and ablation to treat atrial fibrillation, CURRENT OPINION IN CARDIOLOGY, Vol: 30, Pages: 24-32, ISSN: 0268-4705
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- Citations: 10
Petitjean C, Zuluaga MA, Bai W, et al., 2015, Right ventricle segmentation from cardiac MRI: A collation study, MEDICAL IMAGE ANALYSIS, Vol: 19, Pages: 187-202, ISSN: 1361-8415
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- Citations: 152
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
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- Citations: 6
Koa-Wing M, Jamil-Copley S, Ariff B, et al., 2014, Haemorrhagic cerebral air embolism from an atrio-oesophageal fistula following atrial fibrillation ablation., Perfusion, Vol: 30, Pages: 484-486, ISSN: 0935-0020
We report the case of a man found unconscious three weeks following atrial fibrillation (AF) ablation. Cranial and thoracic imaging demonstrated multiple areas of pneumo-embolic infarction secondary to an atrio-oesophageal fistula (AEF). AEF is a recognised, but rare, complication of AF ablation.(1-8) Early recognition is critical as the mortality is 100% without surgical intervention. We consider the postulated mechanisms of AEF formation, the spectrum of clinical presentation, investigations and treatment.
Zaman JAB, Peters NS, 2014, The Rotor Revolution Conduction at the Eye of the Storm in Atrial Fibrillation, CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 7, Pages: 1230-1236, ISSN: 1941-3149
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- Citations: 11
Fry CH, Gray RP, Dhillon PS, et al., 2014, Architectural Correlates of Myocardial Conduction Changes to the Topography of Cellular Coupling, Intracellular Conductance, and Action Potential Propagation with Hypertrophy in Guinea-Pig Ventricular Myocardium, CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 7, Pages: 1198-U333, ISSN: 1941-3149
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- Citations: 13
Van Wagoner DR, Piccini JP, Albert CM, et al., 2014, Progress toward the prevention and treatment of atrial fibrillation: A summary of the Heart Rhythm Society Research Forum on theTreatment and Prevention of Atrial Fibrillation, Washington, DC, December 9-10, 2013, Heart Rhythm, Vol: 12, Pages: E5-E29, ISSN: 1556-3871
The Heart Rhythm Society convened a research symposium on December 9–10, 2013, in Washington, DC, that focused on the prevention of atrial fibrillation (AF) as well as AF-related stroke and morbidity. Attendees sought to summarize advances in understanding AF since a 2008 National Institutes of Health (NIH) conference on this topic1 and to identify continued knowledge gaps and current research priorities. The research symposium also sought to identify key deficiencies and opportunities in research infrastructure, operations, and methodologies.
Ng FS, Holzem KM, Koppel AC, et al., 2014, Adverse Remodeling of the Electrophysiological Response to Ischemia-Reperfusion in Human Heart Failure Is Associated With Remodeling of Metabolic Gene Expression, CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY, Vol: 7, Pages: 875-U234, ISSN: 1941-3149
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- Citations: 19
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.
Cantwell C, Roney CH, Ali RL, et al., 2014, A Software Platform for the Comparative Analysis of Electroanatomic and Imaging Data including Conduction Velocity Mapping, IEEE Engineering in Medicine and Biology Conference
Electroanatomic mapping systems collect increasingly large quantities of spatially-distributed electrical data which may be potentially further scrutinized post-operatively to expose mechanistic properties which sustain and perpetuate atrial fibrillation. We describe a modular software platform, developed to post-process and rapidly analyse data exported from electroanatomic mapping systems using a range of existing and novel algorithms. Imaging data highlighting regions of scar can also be overlaid for comparison. In particular, we describe the conduction velocity mapping algorithm used to highlight wavefront behaviour. Conduction velocity was found to be particularly sensitive to the spatial distribution of the triangulation points and corresponding activation times. A set of geometric conditions were devised for selecting suitable triangulations of the electrogram set for generating CV maps.
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