Publications by authors named "Remi Dubois"

91 Publications

Ultralow temperature cryoablation: Safety and efficacy of preclinical atrial and ventricular lesions.

J Cardiovasc Electrophysiol 2021 Mar 1;32(3):570-577. Epub 2021 Feb 1.

IHU LIRYC ANR-10-IAHU-04, Electrophysiology and Heart Modeling Institute, University of Bordeaux, Bordeaux-Pessac, France.

Background: Ultralow temperature cyroablation (ULTC) is designed to create focal, linear, and circumferential lesions. The aim of this study was to assess the safety, efficacy, and durability of atrial and ventricular ULTC lesions in preclinical large animal models.

Methods And Results: The ULTC system uses nitrogen near its liquid-vapor critical point to cool 11-cm ablation catheters. The catheter can be shaped to specific anatomies using pre-shaped stylets. ULTC was used in 11 swine and four sheep to create atrial (pulmonary vein isolation and linear ablation) and ventricular lesions. Acute and 90-day success were evaluated by intracardiac mapping and histologic examination. Cryoadherence was observed during all ULTC applications, ensuring catheter stability at target locations. Local electrograms were completely eliminated immediately after the first single-shot ULTC application in 49 of 53 (92.5%) atrial and in 31 of 32 (96.9%) ventricular applications. Lesion depth as measured on histology preparations was 1.96 ± 0.8 mm in atrial and 5.61 ± 2.2 mm in ventricular lesions. In all animals, voltage maps and histology demonstrated transmural and durable lesions without gaps, surrounded by intact collagen fibers without injury to surrounding tissues. Transient coronary spasm could be provoked with endocardial ULTC in the left ventricle in close proximity to a coronary artery.

Conclusions: ULTC created effective and efficient atrial and ventricular lesions in vivo without procedural complications in two large animal models. ULTC lesions were transmural, contiguous, and durable over 3 months.
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http://dx.doi.org/10.1111/jce.14907DOI Listing
March 2021

Automated rhythm-based control of radiofrequency ablation close to the atrioventricular node: Preclinical, animal, and first-in-human testing.

Heart Rhythm 2020 Oct 20. Epub 2020 Oct 20.

L'Institut de RYthmologie et Modélisation Cardiaque (LIRYC), Pessac, Bordeaux, France; Cardiology Department, Hôpital Haut-Lévèque, Pessac, Bordeaux, France.

Background: The risk of heart block during radiofrequency ablation of atrioventricular (AV) nodal reentrant tachycardia and septal accessory pathways is minimized by rapidly ceasing ablation in response to markers of risk, such as atrioventricular dissociation, fast junctional rhythm, PR interval prolongation, or 2 consecutive atrial or ventricular depolarizations. Currently this is done manually.

Objectives: The objectives of this study were to build and test a control system able to monitor cardiac rhythm and automatically terminate ablation energy when required.

Methods: The device was built from off-shelf componentry. Preclinical testing involved real-time input of electrogram/electrocardiogram data from 209 ablation procedures (20 patients) over slow (n = 19) and fast (n = 1) AV nodal pathways. The device response speed was compared with the human response speed. The device's ability to prevent heart block was tested in 5 sheep. First-in-human testing was then performed in 12 patients undergoing AV nodal reentrant tachycardia ablation.

Results: Risk conditions necessitating shutoff of ablation (200 total; 111 preclinical and 89 first-in-human) were detected by the device with 100% sensitivity and 94% specificity, automatically terminating ablation while still allowing successful ablation in all patients. Device shutoff of ablation was always faster than human response (median difference 1.24 seconds). In each of 5 sheep, 40 consecutive attempts to cause heart block by ablating over the His bundle were unsuccessful because of automatic shutoff in response to rhythm change.

Conclusion: Automated shutoff of ablation close to the AV node in response to markers of the risk of heart block is feasible with high accuracy as well as faster response than human response. The system may improve the safety of ablation near the AV node by preventing heart block.
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http://dx.doi.org/10.1016/j.hrthm.2020.10.014DOI Listing
October 2020

Insights Into the Spatiotemporal Patterns of Complexity of Ventricular Fibrillation by Multilead Analysis of Body Surface Potential Maps.

Front Physiol 2020 23;11:554838. Epub 2020 Sep 23.

Institute of Electrophysiology and Heart Modeling (IHU Liryc), Foundation Bordeaux University, Bordeaux, France.

Background: Ventricular fibrillation (VF) is the main cause of sudden cardiac death, but its mechanisms are still unclear. We propose a noninvasive approach to describe the progression of VF complexity from body surface potential maps (BSPMs).

Methods: We mapped 252 VF episodes (16 ± 10 s) with a 252-electrode vest in 110 patients (89 male, 47 ± 18 years): 50 terminated spontaneously, otherwise by electrical cardioversion (DCC). Changes in complexity were assessed between the onset ("VF start") and the end ("VF end") of VF by the nondipolar component index ( ), measuring the fraction of energy nonpreserved by an equivalent 3D dipole from BSPMs. Higher NDI reflected lower VF organization. We also examined other standard body surface markers of VF dynamics, including fibrillatory wave amplitude ( ), surface cycle length ( ) and Shannon entropy ( ). Differences between patients with and without structural heart diseases (SHD, 32 vs. NSHD, 78) were also tested at those stages. Electrocardiographic features were validated with simultaneous endocardium cycle length (CL) in a subset of 30 patients.

Results: All BSPM markers measure an increase in electrical complexity during VF ( < 0.0001), and more significantly in NSHD patients. Complexity is significantly higher at the end of sustained VF episodes requiring DCC. Intraepisode intracardiac CL shortening (VF start 197 ± 24 vs. VF end 169 ± 20 ms; < 0.0001) correlates with an increase in NDI, and decline in surface CL, f-wave amplitude, and entropy ( < 0.0001). In SHD patients VF is initially more complex than in NSHD patients ( , = 0.0007; , < 0.0001), with moderately slower ( , = 0.06), low-amplitude f-waves ( , < 0.0001). In this population, lower NDI ( = 0.004) and slower surface CL ( = 0.008) at early stage of VF predict self-termination. In the NSHD group, a more abrupt increase in VF complexity is quantified by all BSPM parameters during sustained VF ( < 0.0001), whereas arrhythmia evolution is stable during self-terminating episodes, hinting at additional mechanisms driving VF dynamics.

Conclusion: Multilead BSPM analysis underlines distinct degrees of VF complexity based on substrate characteristics.
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http://dx.doi.org/10.3389/fphys.2020.554838DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7538856PMC
September 2020

Critical repolarization gradients determine the induction of reentry-based torsades de pointes arrhythmia in models of long QT syndrome.

Heart Rhythm 2021 Feb 5;18(2):278-287. Epub 2020 Oct 5.

Department of Clinical and Experimental Cardiology, Amsterdam UMC, AMC, Amsterdam, The Netherlands; Electrophysiology and Heart Modeling Institute, IHU Liryc, Fondation Bordeaux Université, Pessac-Bordeaux, France.

Background: Torsades de pointes arrhythmia is a potentially lethal polymorphic ventricular tachyarrhythmia (pVT) in the setting of long QT syndrome. Arrhythmia susceptibility is influenced by risk factors modifying repolarization.

Objective: The purpose of this article was to characterize repolarization duration and heterogeneity in relation to pVT inducibility and maintenance.

Methods: Sotalol was infused regionally or globally in isolated Langendorff blood-perfused pig hearts (N = 7) to create repolarization time (RT) heterogeneities. Programmed stimulation and epicardial activation and repolarization mapping were performed. The role of RT (heterogeneities) was studied in more detail using a computer model of the human heart.

Results: pVTs (n = 11) were inducible at a critical combination of RT and RT heterogeneities. The pVT cycle lengths were similar in the short and long RT regions. Short-lasting pVTs were maintained by focal activity while longer-lasting pVTs by reentry wandering along the interface between the 2 regions. Local restitution curves from the long and short RT regions crossed. This was associated with T-wave inversion at coupling intervals at either side of the crossing point. These experimental observations were confirmed by the computer simulations.

Conclusion: pVTs are inducible within a critical range of RT and RT heterogeneities and are maintained by reentry wandering along the repolarization gradient. Double potentials localize at the core of the reentrant circuit and reflect phase singularities. RT gradient and T waves invert with short-coupled premature beats in the long RT region as a result of the crossing of the restitution curves allowing reentry initiation.
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http://dx.doi.org/10.1016/j.hrthm.2020.09.020DOI Listing
February 2021

Long-Lasting Ventricular Fibrillation in Humans ECG Characteristics and Effect of Radiofrequency Ablation.

Circ Arrhythm Electrophysiol 2020 10 10;13(10):e008639. Epub 2020 Sep 10.

LIRYC Institute/INSERM 1045, Bordeaux University, France (J.D., M. Hocini, F.S., P.J., O.B., M. Haïssaguerre, R.D.).

Background: Studies of ventricular fibrillation (VF) in humans are limited because of the short available duration. We sought to study surface ECG waveforms and effect of ablation in long-lasting VF in patients with left assist devices.

Methods: Continuous 12-lead ECG of 5 episodes of long-lasting VF occurring in 3 patients with left ventricular assist device were analyzed. Spectral analysis (dominant frequency) and quantification of waveform amplitude, regularity (Unbiased Regularity Index), and complexity (Nondipolar Index) were performed over a median of 24 minutes of VF. Radiofrequency ablation was performed during VF in 2 patients.

Results: There was a significant increase in dominant frequency between VF onset and termination but none of the other parameters significantly changed. Some VF parameters varied from patient to patient and from lead to lead. Dominant frequency decreased after radiofrequency ablation in both cases and VF terminated spontaneously shortly after ablation in one case. The previously incessant VFs in these 2 patients did not recur afterward.

Conclusions: VF rate increases over time in patients with left ventricular assist devices and is lowered by ablation. Long-lasting VF may be modified or even terminated by ablation.
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http://dx.doi.org/10.1161/CIRCEP.120.008639DOI Listing
October 2020

Body Surface Mapping of Ventricular Repolarization Heterogeneity: An Multiparameter Study.

Front Physiol 2020 13;11:933. Epub 2020 Aug 13.

Institute of Electrophysiology and Heart Modeling (IHU Liryc), Foundation Bordeaux University, Pessac-Bordeaux, France.

Background: Increased heterogeneity of ventricular repolarization is associated with life-threatening arrhythmia and sudden cardiac death (SCD). T-wave analysis through body surface potential mapping (BSPM) is a promising tool for risk stratification, but the clinical effectiveness of current electrocardiographic indices is still unclear, with limited experimental validation. This study aims to investigate performance of non-invasive state-of-the-art and novel T-wave markers for repolarization dispersion in an model.

Methods: Langendorff-perfused pig hearts ( = 7) were suspended in a human-shaped 256-electrode torso tank. Tank potentials were recorded during sinus rhythm before and after introducing repolarization inhomogeneities through local perfusion with dofetilide and/or pinacidil. Drug-induced repolarization gradients were investigated from BSPMs at different experiment phases. Dispersion of electrical recovery was quantified by duration parameters, i.e., the time interval between the peak and the offset of T-wave (T-T) and QT interval, and variability over time and electrodes was also assessed. The degree of T-wave symmetry to the peak was quantified by the ratio between the terminal and initial portions of T-wave area (). Morphological variability between left and right BSPM electrodes was measured by dynamic time warping (DTW). Finally, T-wave organization was assessed by the complexity of repolarization index (CR), i.e., the amount of energy non-preserved by the dominant eigenvector computed by principal component analysis (PCA), and the error between each multilead T-wave and its 3D PCA approximation (NMSE). Body surface indices were compared with global measures of epicardial dispersion of repolarization, and with local gradients between adjacent ventricular sites.

Results: After drug intervention, both regional and global repolarization heterogeneity were significantly enhanced. On the body surface, T-T was significantly prolonged and less stable in time in all experiments, while QT interval showed higher variability across the interventions in terms of duration and spatial dispersion. The rising slope of the repolarization profile was steeper, and T-waves were more asymmetric than at baseline. Interventricular shape dissimilarity was enhanced by repolarization gradients according to DTW. Organized T-wave patterns were associated with abnormal repolarization, and they were properly described by the first principal components.

Conclusion: Repolarization heterogeneity significantly affects T-wave properties, and can be non-invasively captured by BSPM-based metrics.
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http://dx.doi.org/10.3389/fphys.2020.00933DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7438571PMC
August 2020

Idiopathic Ventricular Fibrillation: Role of Purkinje System and Microstructural Myocardial Abnormalities.

JACC Clin Electrophysiol 2020 06;6(6):591-608

Institut Hospitalo-Universitaire Electrophysiology and Heart Modeling Institute, Centre Hospitalier Universitaire de Bordeaux, France; Cardiothoracic Research Center Bordeaux, Université de Bordeaux, Bordeaux, France.

Idiopathic ventricular fibrillation is diagnosed in patients who survived a ventricular fibrillation episode without any identifiable structural or electrical cause after extensive investigations. It is a common cause of sudden death in young adults. The study reviews the diagnostic value of systematic investigations and the new insights provided by detailed electrophysiological mapping. Recent studies have shown the high incidence of microstructural cardiomyopathic areas, which act as the substrate of ventricular fibrillation re-entries. These subclinical alterations require high-density endo- and epicardial mapping to be identified using electrogram criteria. Small areas are involved and located individually in various sites (mostly epicardial). Their characteristics suggest a variety of genetic or acquired pathological processes affecting cellular connectivity or tissue structure, such as cardiomyopathies, myocarditis, or fatty infiltration. Purkinje abnormalities manifesting as triggering ectopy or providing a substrate for re-entry represent a second important cause. The documentation of ephemeral Purkinje ectopy requires continuous electrocardiography monitoring for diagnosis. A variety of diseases affecting Purkinje cell function or conduction are potentially at play in their pathogenesis. Comprehensive investigations can therefore allow the great majority of idiopathic ventricular fibrillation to ultimately receive diagnoses of a cardiac disease, likely underlain by a mosaic of pathologies. Precise phenotypic characterization has significant implications for interpretation of genetic variants, the risk assessment, and individual therapy. Future improvements in imaging or electrophysiological methods may hopefully allow the identification of the subjects at risk and the development of primary prevention strategies.
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http://dx.doi.org/10.1016/j.jacep.2020.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7308805PMC
June 2020

Electrogram morphology discriminators in implantable cardioverter defibrillators: A comparative evaluation.

J Cardiovasc Electrophysiol 2020 06 7;31(6):1493-1506. Epub 2020 May 7.

Cardio-Thoracic Unit, Bordeaux University Hospital (CHU), Pessac, France.

Background: Morphology algorithms are currently recommended as a standalone discriminator in single-chamber implantable cardioverter defibrillators (ICDs). However, these proprietary algorithms differ in both design and nominal programming.

Objective: To compare three different algorithms with nominal versus advanced programming in their ability to discriminate between ventricular (VT) and supraventricular tachycardia (SVT).

Methods: In nine European centers, VT and SVTs were collected from Abbott, Boston Scientific, and Medtronic dual- and triple-chamber ICDs via their respective remote monitoring portals. Percentage morphology matches were recorded for selected episodes which were classified as VT or SVT by means of atrioventricular comparison. The sensitivity and related specificity of each manufacturer discriminator was determined at various values of template match percentage from receiving operating characteristics (ROC) curve analysis.

Results: A total of 534 episodes were retained for the analysis. In ROC analyses, Abbott Far Field MD (area under the curve [AUC]: 0.91; P < .001) and Boston Scientific RhythmID (AUC: 0.95; P < .001) show higher AUC than Medtronic Wavelet (AUC: 0.81; P < .001) when tested for their ability to discriminate VT from SVT. At nominal % match threshold all devices provided high sensitivity in VT identification, (91%, 100%, and 90%, respectively, for Abbott, Boston Scientific, and Medtronic) but contrasted specificities in SVT discrimination (85%, 41%, and 62%, respectively). Abbott and Medtronic's nominal thresholds were similar to the optimal thresholds. Optimization of the % match threshold improved the Boston Scientific specificity to 79% without compromising the sensitivity.

Conclusion: Proprietary morphology discriminators show important differences in their ability to discriminate SVT. How much this impact the overall discrimination process remains to be investigated.
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http://dx.doi.org/10.1111/jce.14518DOI Listing
June 2020

The Spectrum of Idiopathic Ventricular Fibrillation and J-Wave Syndromes: Novel Mapping Insights.

Card Electrophysiol Clin 2019 12;11(4):699-709

IHU LIRYC, Electrophysiology and Heart Modeling Institute, Avenue du Haut Leveque, Bordeaux 33604, Passes Cedex, France; Univ Bordeaux, CRCTB, U1045, Bordeaux, France.

Idiopathic ventricular fibrillation and J-wave syndromes are causes of sudden cardiac death (SCD) without any identified structural cardiac disease after extensive investigations. Recent data show that high-density electrophysiological mapping may ultimately offer diagnoses of subclinical diseases in most patients including those termed "unexplained" SCD. Three major conditions can underlie the occurrence of SCD: (1) localized depolarization abnormalities (due to microstructural myocardial alteration), (2) Purkinje abnormalities manifesting as triggering ectopy and inducible reentry; or (3) repolarization heterogeneities. Each condition may result from a spectrum of pathophysiologic processes with implications for individual therapy.
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http://dx.doi.org/10.1016/j.ccep.2019.08.011DOI Listing
December 2019

Adriaan van Oosterom, PhD.

Heart Rhythm 2019 10;16(10):e299

L'institut de Rythmologie et Modélisation Cardiaque, Bordeaux, France.

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http://dx.doi.org/10.1016/j.hrthm.2019.06.010DOI Listing
October 2019

Advantages and pitfalls of noninvasive electrocardiographic imaging.

J Electrocardiol 2019 Nov - Dec;57S:S15-S20. Epub 2019 Aug 9.

IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-33600 Pessac, Bordeaux, France; Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, F-33000 Bordeaux, France; INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, F-33000 Bordeaux, France.

Background: With increasing clinical use of Electrocardiographic Imaging (ECGI), it is imperative to understand the limits of this technique. The objective of this study is to evaluate a potential-based ECGI approach for activation and repolarization mapping in sinus rhythm.

Method: Langendorff-perfused pig hearts were suspended in a human-shaped torso tank. Electrograms were recorded with a 108-electrode sock and ECGs with 256 electrodes embedded in the tank surface. Left bundle branch block (LBBB) was developed in 4 hearts through ablation, and repolarization abnormalities in another 4 hearts through regional perfusion of dofetilide and pinacidil. Electrograms were noninvasively reconstructed and reconstructed activation and repolarization features were compared to those recorded.

Results: Visual consistency between ECGI and recorded activation and repolarization maps was high. While reconstructed repolarization times showed significantly more error than activation times quantitatively, patterns were reconstructed with a similar level of accuracy. The number of epicardial breakthrough sites was underestimated by ECGI and these were misplaced (>20 mm) in location. Likewise, ECGI reconstructed activation maps demonstrated artificial lines of block resulting from a W-shaped QRS waveform that were not present in recorded maps. Nevertheless, ECGI allowed identification of regions of abnormal repolarization reasonably accurately in terms of size, location and timing.

Conclusions: This study validates a potential-based ECGI approach to noninvasively image activation and recovery in sinus rhythm. Despite inaccuracies in epicardial breakthroughs and lines of conduction block, other important clinical features such as regions of abnormal repolarization can be accurately derived making ECGI a valuable clinical tool.
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http://dx.doi.org/10.1016/j.jelectrocard.2019.08.007DOI Listing
August 2019

Noninvasive Mapping and Electrocardiographic Imaging in Atrial and Ventricular Arrhythmias (CardioInsight).

Card Electrophysiol Clin 2019 09;11(3):459-471

Cardiac electrophysiology department, Hôpital Haut-Lévêque, 1 Magellan Avenue, Bordeaux, Pessac 33600, France; Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University, avenue Haut Leveque, Pessac 33600, France.

Electrocardiographic imaging is a mapping technique aiming to noninvasively characterize cardiac electrical activity using signals collected from the torso to reconstruct epicardial potentials. Its efficacy has been demonstrated clinically, from mapping premature ventricular complexes and accessory pathways to of complex arrhythmias. Electrocardiographic imaging uses a standardized workflow. Signals should be checked manually to avoid automatic processing errors. Reentry is confirmed in the presence of local activation covering the arrhythmia cycle length. Focal breakthroughs demonstrate a QS pattern associated with centrifugal activation. Electrocardiographic imaging offers a unique opportunity to better understand the mechanism of cardiac arrhythmias and guide ablation.
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http://dx.doi.org/10.1016/j.ccep.2019.05.004DOI Listing
September 2019

Multicenter Evaluation of Clinical Efficacy and Safety of Per-oral Endoscopic Myotomy in Children.

J Pediatr Gastroenterol Nutr 2019 11;69(5):523-527

Gastroenterology, Edouard Herriot Hospital, Hospices Civils de Lyon and Lyon University, Lyon, France.

Objectives: Per-oral endoscopic myotomy (POEM) is a recommended treatment modality for achalasia, but there is little published data for its use in children. The objective of the present study was to evaluate whether POEM is clinically effective and safe for children.

Methods: International multicenter retrospective study conducted in 14 tertiary centers that included consecutive children who underwent POEM between January 2012 and August 2018. Outcomes, such as clinical response were assessed whenever available. Adverse events and factors associated with clinical failure were also investigated.

Results: A total of 117 patients (mean ± SD age: 14.2 ± 3.7 years) underwent POEM for achalasia (type I, n = 36; type II n=66; type III, n=8). Among these, 30 (26%) were pretreated (botulinum injection and/or pneumatic dilatation). Mean ± SD baseline Eckardt score was 7.5 ± 2.0. Clinical success was achieved in 90.6% of cases (95%CI [83.8%;95.2%]) in the intention-to-treat analysis. The mean ± SD Eckardt score post-POEM was 0.9 ± 1.2 (P < 0.001). The mean duration of follow-up time 545 days (range: 100-1612). A total of 7 adverse events occurred (4 mucosotomies, 2 subcutaneous emphysema, 1 esopleural fistula). Gastroesophageal reflux symptoms were seen in 17 patients (15%); missing data for 10 patients (9%). There was a trend towards more frequent clinical failure in achalasia associated with genetic disorders (40% vs 8%, P = 0.069).

Conclusions: POEM in pediatric patients appears to be effective and safe, although there was a trend towards more frequent clinical failure achalasia associated with genetic disorders. Further studies are needed to assess the long-term outcomes, especially the consequences of GERD.
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http://dx.doi.org/10.1097/MPG.0000000000002432DOI Listing
November 2019

Effect of Activation Wavefront on Electrogram Characteristics During Ventricular Tachycardia Ablation.

Circ Arrhythm Electrophysiol 2019 06;12(6):e007293

IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, F-/Bordeaux University Hospital (CHU), Electrophysiology and Ablation Unit, University of Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, France/Pessac-Bordeaux, France (C.A.M., R.M., C.D., M.T., A.F., G.C., N.T., T.K., K.V., M.W., F.B., A.L., J.D., G.M., T.P., A.D., N.D., R.D., M. Hocini, M. Haïssaguerre, P.J., F.S.).

Background Catheter ablation of ventricular tachycardia (VT) in structural heart disease is challenging because of noninducibility or hemodynamic compromise. Ablation often depends on elimination of local abnormal ventricular activities (LAVAs) but which may be hidden in far-field signal. We investigated whether altering activation wavefront affects activation timing and LAVA characterization and allows a better understanding of isthmus anatomy. Methods Patients with ischemic cardiomyopathy underwent mapping using the ultra-high density Rhythmia system (Boston Scientific). Maps were generated for all stable VTs and with pacing from the atrium, right ventricular apex, and an left ventricular branch of the coronary sinus. Results Fifty-six paced maps and 23 VT circuits were mapped in 22 patients. In 79% of activation maps, there was ≥1 line of block in the paced conduction wavefront, with 93% having fixed block and 32% showing functional partial block. Bipolar scar was larger with atrial than right ventricular (31.7±18.5 versus 27.6±16.3 cm, P=0.003) or left ventricular pacing (31.7±18.5 versus 27.0±19.2 cm, P=0.009); LAVA areas were smaller with atrial than right ventricular (12.3±10.5 versus 18.4±11.0 cm, P<0.001) or left ventricular pacing (12.3±10.5 versus 17.1±10.7 cm, P<0.001). LAVA areas were larger with wavefront propagation perpendicular versus parallel to the line of block along isthmus boundaries (19.3±7.1 versus 13.6±7.4 cm, P=0.01). All patients had successful VT isthmus ablation. In 11±8 months follow-up, 2 patients had a recurrence. Conclusions Wavefronts of conduction slowing/block may aid identification of critical isthmuses in unmappable VTs. Altering the activation wavefront leads to significant differences in conduction properties of myocardial tissue, along with scar and LAVA characterization. In patients where few LAVAs are identified during substrate mapping, using an alternate activation wavefront running perpendicular to the VT isthmus may increase sensitivity to detect arrhythmogenic substrate and critical sites for reentry.
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http://dx.doi.org/10.1161/CIRCEP.119.007293DOI Listing
June 2019

Universal atrial coordinates applied to visualisation, registration and construction of patient specific meshes.

Med Image Anal 2019 07 17;55:65-75. Epub 2019 Apr 17.

Institute of Electrophysiology and Heart Modeling (IHU Liryc), Foundation Bordeaux University, Pessac-Bordeaux, France; IMB Bordeaux Institute of Mathematics, University of Bordeaux, 351 cours de la Libération, Talence 33405, France.

Integrating spatial information about atrial physiology and anatomy in a single patient from multimodal datasets, as well as generalizing these data across patients, requires a common coordinate system. In the atria, this is challenging due to the complexity and variability of the anatomy. We aimed to develop and validate a Universal Atrial Coordinate (UAC) system for the following applications: combination and assessment of multimodal data; comparison of spatial data across patients; 2D visualization; and construction of patient specific geometries to test mechanistic hypotheses. Left and right atrial LGE-MRI data were segmented and meshed. Two coordinates were calculated for each atrium by solving Laplace's equation, with boundary conditions assigned using five landmark points. The coordinate system was used to map spatial information between atrial meshes, including scalar fields measured using different mapping modalities, and atrial anatomic structures and fibre directions from a reference geometry. Average error in point transfer from a source mesh to a destination mesh and back again was less than 0.1 mm for the left atrium and 0.02 mm for the right atrium. Patient specific meshes were constructed using the coordinate system and phase singularity density maps from arrhythmia simulations were visualised in 2D. In conclusion, we have developed a universal atrial coordinate system allowing automatic registration of imaging and electroanatomic mapping data, 2D visualisation, and patient specific model creation.
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http://dx.doi.org/10.1016/j.media.2019.04.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6543067PMC
July 2019

Considering New Regularization Parameter-Choice Techniques for the Tikhonov Method to Improve the Accuracy of Electrocardiographic Imaging.

Front Physiol 2019 27;10:273. Epub 2019 Mar 27.

IHU-Liryc, Electrophysiology and Heart Modeling Institute, Foundation Bordeaux Université, Bordeaux, France.

The electrocardiographic imaging (ECGI) inverse problem highly relies on adding constraints, a process called regularization, as the problem is ill-posed. When there are no prior information provided about the unknown epicardial potentials, the Tikhonov regularization method seems to be the most commonly used technique. In the Tikhonov approach the weight of the constraints is determined by the regularization parameter. However, the regularization parameter is problem and data dependent, meaning that different numerical models or different clinical data may require different regularization parameters. Then, we need to have as many regularization parameter-choice methods as techniques to validate them. In this work, we addressed this issue by showing that the Discrete Picard Condition (DPC) can guide a good regularization parameter choice for the two-norm Tikhonov method. We also studied the feasibility of two techniques: The U-curve method (not yet used in the cardiac field) and a novel automatic method, called ADPC due its basis on the DPC. Both techniques were tested with simulated and experimental data when using the method of fundamental solutions as a numerical model. Their efficacy was compared with the efficacy of two widely used techniques in the literature, the L-curve and the CRESO methods. These solutions showed the feasibility of the new techniques in the cardiac setting, an improvement of the morphology of the reconstructed epicardial potentials, and in most of the cases of their amplitude.
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http://dx.doi.org/10.3389/fphys.2019.00273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6445955PMC
March 2019

Optical Imaging of Ventricular Action Potentials in a Torso Tank: A New Platform for Non-Invasive Electrocardiographic Imaging Validation.

Front Physiol 2019 26;10:146. Epub 2019 Feb 26.

IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Bordeaux, France.

Non-invasive electrocardiographic imaging (ECGI) is a promising tool to provide high-resolution panoramic imaging of cardiac electrical activity noninvasively from body surface potential measurements. Current experimental methods for ECGI validation are limited to comparison with unipolar electrograms and the relatively low spatial resolution of cardiac mapping arrays. We aim to develop a novel experimental set up combining a human shaped torso tank with high-resolution optical mapping allowing the validation of ECGI reconstructions. Langendorff-perfused pig hearts ( = 3) were suspended in a human torso-shaped tank, with the left anterior descending artery (LAD) cannulated on a separate perfusion. Electrical signals were recorded from an 108-electrode epicardial sock and 128 electrodes embedded in the tank surface. Simultaneously, optical mapping of the heart was performed through the anterior surface of the tank. Recordings were made in sinus rhythm and ventricular pacing ( = 55), with activation and repolarization heterogeneities induced by perfusion of hot and cold solutions as well as Sotalol through the LAD. Fluoroscopy provided 3D cardiac and electrode geometries in the tank that were transformed to the 2D optical mapping window using an optimization algorithm. Epicardial unipolar electrograms were reconstructed from torso potentials using ECGI and validated using optical activation and repolarization maps. The transformation and alignment of the 3D geometries onto the 2D optical mapping window was good with an average correlation of 0.87 ± 0.10 and error of 7.7 ± 3.1 ms with activation derived from the sock. The difference in repolarization times were more substantial (error = 17.4 ± 3.7 ms) although the sock and optical repolarization patterns themselves were very similar (correlation = 0.83 ± 0.13). Validation of ECGI reconstructions revealed ECGI accurately captures the pattern of activation (correlation = 0.79 ± 0.11) and identified regions of late and/or early repolarization during different perfusions through LAD. ECGI also correctly demonstrated gradients in both activation and repolarization, although in some cases these were under or over-estimated or shifted slightly in space. A novel experimental setup has been developed, combining a human-shaped torso tank with optical mapping, which can be effectively used in the validation of ECGI techniques; including the reconstruction of activation and repolarization patterns and gradients.
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http://dx.doi.org/10.3389/fphys.2019.00146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6399141PMC
February 2019

Reply to the Editor-Interpretation of electrograms is key to understand the clinical potential of ECGi.

Heart Rhythm 2019 06 27;16(6):e52. Epub 2019 Feb 27.

Bordeaux University Hospital and IHU LIRYC, Bordeaux, France; Hôpital Cardiologique du Haut Lévèque, CHU de Bordeaux, Pessac, France.

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http://dx.doi.org/10.1016/j.hrthm.2019.02.029DOI Listing
June 2019

Reply to the Editor-Performance and limitations of noninvasive cardiac activation mapping.

Heart Rhythm 2019 06 7;16(6):e51. Epub 2019 Feb 7.

Bordeaux University Hospital, IHU LIRYC, Bordeaux, France; Hôpital Cardiologique du Haut Lévèque, CHU de Bordeaux, Pessac, France.

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http://dx.doi.org/10.1016/j.hrthm.2019.02.003DOI Listing
June 2019

Impact of the Endocardium in a Parameter Optimization to Solve the Inverse Problem of Electrocardiography.

Front Physiol 2018 22;9:1946. Epub 2019 Jan 22.

IHU Liryc, Electrophysiology and Heart Modeling Institute, Pessac, France.

Electrocardiographic imaging aims at reconstructing cardiac electrical events from electrical signals measured on the body surface. The most common approach relies on the inverse solution of the Laplace equation in the torso to reconstruct epicardial potential maps from body surface potential maps. Here we apply a method based on a parameter identification problem to reconstruct both activation and repolarization times. From an ansatz of action potential, based on the Mitchell-Schaeffer ionic model, we compute body surface potential signals. The inverse problem is reduced to the identification of the parameters of the Mitchell-Schaeffer model. We investigate whether solving the inverse problem with the endocardium improves the results or not. We solved the parameter identification problem on two different meshes: one with only the epicardium, and one with both the epicardium and the endocardium. We compared the results on both the heart (activation and repolarization times) and the torso. The comparison was done on validation data of sinus rhythm and ventricular pacing. We found similar results with both meshes in 6 cases out of 7: the presence of the endocardium slightly improved the activation times. This was the most visible on a sinus beat, leading to the conclusion that inclusion of the endocardium would be useful in situations where endo-epicardial gradients in activation or repolarization times play an important role.
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http://dx.doi.org/10.3389/fphys.2018.01946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6349712PMC
January 2019

Characterizing localized reentry with high-resolution mapping: Evidence for multiple slow conducting isthmuses within the circuit.

Heart Rhythm 2019 05 28;16(5):679-685. Epub 2018 Nov 28.

Hôpital Haut Leveque, Pessac, France; LIRYC Institute, Pessac, France.

Background: Reentrant circuits are considered to be critically dependent on a single protected slow conducting isthmus.

Objective: The purpose of this study was to investigate conduction properties and electrogram (EGM) characteristics of the entire circuit in localized atrial reentrant circuits using high-resolution mapping.

Methods: Fifteen localized reentrant atrial tachycardias were studied with high-resolution mapping (Rhythmia). EGMs along the entire circuit were analyzed offline for fractionation, duration, and amplitude. Maps were exported to MATLAB (MathWorks) to measure bipolar voltage and conduction velocities (CVs) within the circuit. Slow conduction was defined as <30 cm/s.

Results: Fifteen localized re-entrant circuits (12 left atrial, 3 right atrial) with mean cycle length 273 ± 40 ms were analyzed using high-resolution maps (22,389 ± 13,375 EGMs). A mean of 4.5 ± 1.6 slow conduction corridors were identified per circuit. Although the entire circuit was of low voltage, the bipolar voltage in slow conducting corridors was significantly lower than the rest of the circuit (0.22 ± 0.20 mV vs 0.50 ± 0.48 mV; P <.001). The mean conduction velocity of the circuit, excluding slow conduction areas, was 90.3 ± 34.3 cm/s vs 13.9 ± 3.5 cm/s (P <.001) in the slow conduction corridors. EGM analysis at the slowest conduction corridors demonstrated fractionation (100%) with longer EGM duration compared to the other slow conduction corridors along the circuit (99 ± 9 ms vs 74 ± 11 ms; P = .003).

Conclusion: In contrast to current understanding, localized atrial reentrant circuits have multiple sequential "corridors" of very slow conduction (2-7) that contribute to maintenance of arrhythmia. The localized reentry occurs in low-voltage areas, with voltage further reduced in these multiple slow conducting corridors.
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http://dx.doi.org/10.1016/j.hrthm.2018.11.027DOI Listing
May 2019

Fast personalized electrophysiological models from computed tomography images for ventricular tachycardia ablation planning.

Europace 2018 Nov;20(suppl_3):iii94-iii101

Université Côte d'Azur, Inria, Epione, Sophia Antipolis, France.

Aims: Clinical application of patient-specific cardiac computer models requires fast and robust processing pipelines that can be seamlessly integrated into clinical workflows. We aim at building such a pipeline from computed tomography (CT) images to personalized cardiac electrophysiology (EP) model. The simulation output could be useful in the context of post-infarct ventricular tachycardia (VT) radiofrequency ablation (RFA) planning for pre-operative targets prediction.

Methods And Results: The support for model personalization is a patient-specific virtual three-dimensional heart obtained from CT images. Here, the scar is identified as thinning of the myocardial wall on automatically computed thickness maps. We then use an Eikonal model of wave front propagation with reduced velocity in the damaged areas. An image-based vessel enhancement algorithm can automatically identify VT isthmuses. The personalized model is used for virtual pacing. We obtained a very fast pipeline that enables simulations in only a few minutes. It is fully automated starting from the semi-automated image segmentation phase. The computational time frame is compatible with the construction of a virtual pacing tool. In this tool, onset points and an optional directional block could be interactively selected. The directional block is a simple way to model tissue refractoriness. Output activation maps are compared with EP data acquired pre-operatively. We show that this framework allows the reproduction of recorded re-entrant VT activation patterns.

Conclusion: Our simulation framework has an application in VT RFA intervention planning. It could be used to guide EP explorations and even predict ablation targets pre-operatively. This could reduce intervention duration and improve success rate.
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http://dx.doi.org/10.1093/europace/euy228DOI Listing
November 2018

Depolarization versus repolarization abnormality underlying inferolateral J-wave syndromes: New concepts in sudden cardiac death with apparently normal hearts.

Heart Rhythm 2019 05 2;16(5):781-790. Epub 2018 Nov 2.

IHU LIRYC, Electrophysiology and Heart Modeling Institute, Bordeaux, France; University of Bordeaux, U1045, Bordeaux, France.

Early repolarization indicates a distinct electrocardiographic phenotype affecting the junction between the QRS complex and the ST segment in inferolateral leads (inferolateral J-wave syndromes). It has been considered a benign electrocardiographic variant for decades, but recent clinical studies have demonstrated its arrhythmogenicity in a small subset, supported by experimental studies showing transmural dispersion of repolarization. Here we review the current knowledge and the issues of risk stratification that limit clinical management. In addition, we report on new mapping data of patients refractory to pharmacologic treatment using high-density electrogram mapping at the time of inscription of J wave. These data demonstrate that distinct substrates, delayed depolarization, and abnormal early repolarization underlie inferolateral J-wave syndromes, with significant implications. Finally, based on these data, we propose a new simplified mechanistic classification of sudden cardiac deaths without apparent structural heart disease.
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http://dx.doi.org/10.1016/j.hrthm.2018.10.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6486498PMC
May 2019

Performance and limitations of noninvasive cardiac activation mapping.

Heart Rhythm 2019 03 26;16(3):435-442. Epub 2018 Oct 26.

IHU LIRYC, Bordeaux University, Bordeaux, France.

Background: Activation mapping using noninvasive electrocardiographic imaging (ECGi) has recently been used to describe the physiology of different cardiac abnormalities. These descriptions differ from prior invasive studies, and both methods have not been thoroughly confronted in a clinical setting.

Objective: The goal of the present study was to provide validation of noninvasive activation mapping in a clinical setting through direct confrontation with invasive epicardial contact measures.

Methods: Fifty-nine maps were obtained in 55 patients and aligned on a common geometry. Nearest-neighbor interpolation was used to avoid map smoothing. Quantitative comparison was performed by computing between-map correlation coefficients and absolute activation time errors.

Results: The mean activation time error was 20.4 ± 8.6 ms, and the between-map correlation was poor (0.03 ± 0.43). The results suggested high interpatient variability (correlation -0.68 to 0.82), wide QRS patterns, and paced rhythms demonstrating significantly better mean correlation (0.68 ± 0.17). Errors were greater in scarred regions (21.9 ± 10.8 ms vs 17.5 ± 6.7 ms; P < .01). Fewer epicardial breakthroughs were imaged using noninvasive mapping (1.3 ± 0.5 vs 2.3 ± 0.7; P < .01). Primary breakthrough locations were imaged 75.7 ± 38.1 mm apart. Lines of conduction block (jumps of ≥50 ms between contiguous points) due to structural anomalies were recorded in 27 of 59 contact maps and were not visualized at these same sites noninvasively. Instead, artificial lines appeared in 33 of 59 noninvasive maps in regions of reduced bipolar voltage amplitudes (P = .03). An in silico model confirms these artificial constructs.

Conclusion: Overall, agreement of ECGi activation mapping and contact mapping is poor and heterogeneous. The between-map correlation is good for wide QRS patterns. Lines of block and epicardial breakthrough sites imaged using ECGi are inaccurate. Further work is required to improve the accuracy of the technique.
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http://dx.doi.org/10.1016/j.hrthm.2018.10.010DOI Listing
March 2019

Characteristics of Scar-Related Ventricular Tachycardia Circuits Using Ultra-High-Density Mapping: A Multi-Center Study.

Circ Arrhythm Electrophysiol 2018 10;11(10):e006569

LIRYC Institute/INSERM 1045, Bordeaux University Hospital (R.M., C.D., C.A.M., M.T., A.F., N.T., T.K., K.V., M.W., G.C., J.D., G.M., T.P., A.D., N.D., M. Hocini, M. Haïssaguerre, P.J., R.D., F.S.).

Background: Ventricular tachycardia (VT) with structural heart disease is dependent on reentry within scar regions. We set out to assess the VT circuit in greater detail than has hitherto been possible, using ultra-high-density mapping.

Methods: All ultra-high-density mapping guided VT ablation cases from 6 high-volume European centers were assessed. Maps were analyzed offline to generate activation maps of tachycardia circuits. Topography, conduction velocity, and voltage of the VT circuit were analyzed in complete maps.

Results: Thirty-six tachycardias in 31 patients were identified, 29 male and 27 ischemic. VT circuits and isthmuses were complex, 11 were single loop and 25 double loop; 3 had 2 entrances, 5 had 2 exits, and 15 had dead ends of activation. Isthmuses were defined by barriers, which included anatomic obstacles, lines of complete block, and slow conduction (in 27/36 isthmuses). Median conduction velocity was 0.08 m/s in entrance zones, 0.29 m/s in isthmus regions ( P<0.001), and 0.11 m/s in exit regions ( P=0.002). Median local voltage in the isthmus was 0.12 mV during tachycardia and 0.06 mV in paced/sinus rhythm. Two circuits were identifiable in 5 patients. The median timing of activation was 16% of diastole in entrances, 47% in the mid isthmus, and 77% in exits.

Conclusions: VT circuits identified were complex, some of them having multiple entrances, exits, and dead ends. The barriers to conduction in the isthmus seem to be partly functional in 75% of circuits. Conduction velocity in the VT isthmus slowed at isthmus entrances and exits when compared with the mid isthmus. Isthmus voltage is often higher in VT than in sinus or paced rhythms.
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http://dx.doi.org/10.1161/CIRCEP.118.006569DOI Listing
October 2018

Mapping and Ablation of Idiopathic Ventricular Fibrillation.

Front Cardiovasc Med 2018 18;5:123. Epub 2018 Sep 18.

Electrophysiology and Ablation Unit, Bordeaux University Hospital (CHU), Pessac, France.

Idiopathic ventricular fibrillation (IVF) is the main cause of unexplained sudden cardiac death, particularly in young patients under the age of 35. IVF is a diagnosis of exclusion in patients who have survived a VF episode without any identifiable structural or metabolic causes despite extensive diagnostic testing. Genetic testing allows identification of a likely causative mutation in up to 27% of unexplained sudden deaths in children and young adults. In the majority of cases, VF is triggered by PVCs that originate from the Purkinje network. Ablation of VF triggers in this setting is associated with high rates of acute success and long-term freedom from VF recurrence. Recent studies demonstrate that a significant subset of IVF defined by negative comprehensive investigations, demonstrate in fact subclinical structural alterations. These localized myocardial alterations are identified by high density electrogram mapping, are of small size and are mainly located in the epicardium. As reentrant VF drivers are often colocated with regions of abnormal electrograms, this localized substrate can be shown to be mechanistically linked with VF. Such areas may represent an important target for ablation.
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http://dx.doi.org/10.3389/fcvm.2018.00123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6153961PMC
September 2018

Wavelength and Fibrosis Affect Phase Singularity Locations During Atrial Fibrillation.

Front Physiol 2018 10;9:1207. Epub 2018 Sep 10.

IMB, UMR 5251, University of Bordeaux, Pessac, France.

The mechanisms underlying atrial fibrillation (AF), the most common sustained cardiac rhythm disturbance, remain elusive. Atrial fibrosis plays an important role in the development of AF and rotor dynamics. Both electrical wavelength (WL) and the degree of atrial fibrosis change as AF progresses. However, their combined effect on rotor core location remains unknown. The aim of this study was to analyze the effects of WL change on rotor core location in both fibrotic and non-fibrotic atria. Three patient specific fibrosis distributions (total fibrosis content: 16.6, 22.8, and 19.2%) obtained from clinical imaging data of persistent AF patients were incorporated in a bilayer atrial computational model. Fibrotic effects were modeled as myocyte-fibroblast coupling + conductivity remodeling; structural remodeling; ionic current changes + conductivity remodeling; and combinations of these methods. To change WL, action potential duration (APD) was varied from 120 to 240ms, representing the range of clinically observed AF cycle length, by modifying the inward rectifier potassium current () conductance between 80 and 140% of the original value. Phase singularities (PSs) were computed to identify rotor core locations. Our results show that conductance variation resulted in a decrease of APD and WL across the atria. For large WL in the absence of fibrosis, PSs anchored to regions with high APD gradient at the center of the left atrium (LA) anterior wall and near the junctions of the inferior pulmonary veins (PVs) with the LA. Decreasing the WL induced more PSs, whose distribution became less clustered. With fibrosis, PS locations depended on the fibrosis distribution and the fibrosis implementation method. The proportion of PSs in fibrotic areas and along the borders varied with both WL and fibrosis modeling method: for patient one, this was 4.2-14.9% as varied for the structural remodeling representation, but 12.3-88.4% using the combination of structural remodeling with myocyte-fibroblast coupling. The degree and distribution of fibrosis and the choice of implementation technique had a larger effect on PS locations than the WL variation. Thus, distinguishing the fibrotic mechanisms present in a patient is important for interpreting clinical fibrosis maps to create personalized models.
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http://dx.doi.org/10.3389/fphys.2018.01207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6139329PMC
September 2018

Noninvasive Assessment of Atrial Fibrillation Complexity in Relation to Ablation Characteristics and Outcome.

Front Physiol 2018 17;9:929. Epub 2018 Jul 17.

Institute of Electrophysiology and Heart Modeling (IHU Liryc), Foundation Bordeaux University, Pessac-Bordeaux, France.

The use of surface recordings to assess atrial fibrillation (AF) complexity is still limited in clinical practice. We propose a noninvasive tool to quantify AF complexity from body surface potential maps (BSPMs) that could be used to choose patients who are eligible for AF ablation and assess therapy impact. BSPMs (mean duration: 7 ± 4 s) were recorded with a 252-lead vest in 97 persistent AF patients (80 male, 64 ± 11 years, duration 9.6 ± 10.4 months) before undergoing catheter ablation. Baseline cycle length (CL) was measured in the left atrial appendage. The procedural endpoint was AF termination. The ablation strategy impact was defined in terms of number of regions ablated, radiofrequency delivery time to achieve AF termination, and acute outcome. The atrial fibrillatory wave signal extracted from BSPMs was divided in 0.5-s consecutive segments, each projected on a 3D subspace determined through principal component analysis (PCA) in the current frame. We introduced the nondipolar component index (NDI) that quantifies the fraction of energy retained after subtracting an equivalent PCA dipolar approximation of heart electrical activity. AF complexity was assessed by the NDI averaged over the entire recording and compared to ablation strategy. AF terminated in 77 patients (79%), whose baseline AF CL was 177 ± 40 ms, whereas it was 157 ± 26 ms in patients with unsuccessful ablation outcome ( = 0.0586). Mean radiofrequency emission duration was 35 ± 21 min; 4 ± 2 regions were targeted. Long-lasting AF patients (≥12 months) exhibited higher complexity, with higher NDI values (≥12 months: 0.12 ± 0.04 vs. <12 months: 0.09 ± 0.03, < 0.01) and short CLs (<160 ms: 0.12 ± 0.03 vs. between 160 and 180 ms: 0.10 ± 0.03 vs. >180 ms: 0.09 ± 0.03, < 0.01). More organized AF as measured by lower NDI was associated with successful ablation outcome (termination: 0.10 ± 0.03 vs. no termination: 0.12 ± 0.04, < 0.01), shorter procedures (<30 min: 0.09 ± 0.04 vs. ≥30 min: 0.11 ± 0.03, < 0.001) and fewer ablation targets (<4: 0.09 ± 0.03 vs. ≥4: 0.11 ± 0.04, < 0.01). AF complexity can be noninvasively quantified by PCA in BSPMs and correlates with ablation outcome and AF pathophysiology.
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http://dx.doi.org/10.3389/fphys.2018.00929DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056813PMC
July 2018

Localized Structural Alterations Underlying a Subset of Unexplained Sudden Cardiac Death.

Circ Arrhythm Electrophysiol 2018 07;11(7):e006120

IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, France (M. Haïssaguerre, M. Hocini, G.C., J.D., F.S., S.P., H.C., M.T., A.D., R.M., N.D., P.B., P.R., S.P., T.P., N.K., G.M., X.P., C.D., L.L., R.C., P.J., D.B., E.V., M.P., R.W., O.B., R.D.).

Background: Sudden cardiac death because of ventricular fibrillation (VF) is commonly unexplained in younger victims. Detailed electrophysiological mapping in such patients has not been reported.

Methods: We evaluated 24 patients (29±13 years) who survived idiopathic VF. First, we used multielectrode body surface recordings to identify the drivers maintaining VF. Then, we analyzed electrograms in the driver regions using endocardial and epicardial catheter mapping during sinus rhythm. Established electrogram criteria were used to identify the presence of structural alterations.

Results: VF occurred spontaneously in 3 patients and was induced in 16, whereas VF was noninducible in 5. VF mapping demonstrated reentrant and focal activities (87% versus 13%, respectively) in all. The activities were dominant in one ventricle in 9 patients, whereas they had biventricular distribution in others. During sinus rhythm areas of abnormal electrograms were identified in 15/24 patients (62.5%) revealing localized structural alterations: in the right ventricle in 11, the left ventricle in 1, and both in 3. They covered a limited surface (13±6 cm) representing 5±3% of the total surface and were recorded predominantly on the epicardium. Seventy-six percent of these areas were colocated with VF drivers (<0.001). In the 9 patients without structural alteration, we observed a high incidence of Purkinje triggers (7/9 versus 4/15, =0.033). Catheter ablation resulted in arrhythmia-free outcome in 15/18 patients at 17±11 months follow-up.

Conclusions: This study shows that localized structural alterations underlie a significant subset of previously unexplained sudden cardiac death. In the other subset, Purkinje electrical pathology seems as a dominant mechanism.
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http://dx.doi.org/10.1161/CIRCEP.117.006120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7661047PMC
July 2018

Cardiac Propagation Pattern Mapping With Vector Field for Helping Tachyarrhythmias Diagnosis With Clinical Tridimensional Electro-Anatomical Mapping Tools.

IEEE Trans Biomed Eng 2019 02 28;66(2):373-382. Epub 2018 May 28.

Ventricular (VT) and atrial (AT) tachycardias are some of the most common clinical cardiac arrhythmias. For ablation of tachycardia substrates, two clinical diagnosis methods are used: invasive electroanatomical mapping for an accurate diagnosis using electrograms (EGMs) acquired with intracardiac catheters, and localized on the surface mesh of the studied cavities; and noninvasive electrocardiographic imaging (ECGi) for a global view of the arrhythmia, with EGMs mathematically reconstructed from body surface electrocardiograms using 3-D cardio-thoracic surface meshes obtained from CT-scans. In clinics, VT and AT are diagnosed by studying activation time maps that depict the propagation of the activation wavefront on the cardiac mesh. Nevertheless, slow conduction areas-a well-known proarrhythmic feature for tachycardias-and tachycardia specific propagation patterns are not easily identifiable with these maps. Therefore, local characterization of the activation wavefront propagation can be helpful for improving VT and AT diagnoses. The purpose of this study is to develop a method to locally characterize the activation wavefront propagation for clinical data. For this, a conduction velocity vector field is estimated and analyzed using divergence and curl mathematical operators. The workflow was first validated on a simulated database from computer models, and then applied to a clinical database obtained from ECGi to improve AT diagnosis. The results show the relevancy and the efficacy of the proposed method to guide ablation of tachyarrhythmias.
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http://dx.doi.org/10.1109/TBME.2018.2841340DOI Listing
February 2019