Caractéristiques et traitements des cicatrices myocardiques responsables d'arythmie ventriculaire

Radiofrequency (RF) catheter ablation is a recognized treatment for ventricular tachycardia(VT) in patients with structural heart disease. Even if it can be life saving, success rateremains around 53 to 67%.We aimed to better characterized VT substrate in patients with ischemic cardiomyopathy(CMP), non ischemic CMP with subepicardial scar, left ventricular assist device and Brugadasyndrome. We also evaluate the efficacy of new technologies (such as contact force), specificapproaches (epicardial access, intra coronary alcohol ablation), systematic use of cardiacimaging and new end-points for VT ablation.We demonstrated that each substrate had specific electrophysiological properties that helpoptimizing the mapping and the ablation in these patients. We also showed the interest of(1) new technologies to improve RF lesion formation; (2) specific approaches in selectedpatients to eradicate the VT substrate; and (3) cardiac imaging to help identifying thesubstrate and preventing complications. Finally using local abnormal ventricular potentialelimination as an end-point for VT ablation is feasible and associated with lower mortalityduring follow-up when achieved.Knowledge of substrate specificities, use of contact force, cardiac imaging, epicardial accessin selected patients and scar homogenization improve VT ablation efficacy and/or safety.L’ablation par radiofréquence percutanée est un des traitements des tachycardiesventriculaires (TV). Bien que salvateur chez certains patients avec myocardiopathie (MCP),les taux de succès rapportés varient de 53 à 67% dans les centres entrainés.Le but de ce travail est d’essayer de mieux comprendre le substrat des arythmiesventriculaires et d’en améliorer le traitement. Pour cela, nous avons étudié le substrat despatients adressés pour ablation de TV (sur MCP ischémique, sur MCP dilatée à coronairessaines avec cicatrices sous épicardiques, chez les patients avec assistance ventriculairegauche et chez un patient avec syndrome de Brugada). Nous avons également évalué etproposé des outils/attitudes thérapeutiques pour essayer d’améliorer le traitement des TV.Nous avons mis en évidence des particularités électrophysiologiques pour chacun de cessubstrats qui permettent d’optimiser et d’adapter la cartographie et l’ablation chez cespatients. Par ailleurs, nous avons montré l’intérêt : (1) de nouvelles technologies pouraméliorer l’efficacité de l’ablation ; (2) des approches épicardiques ou d’alcoolisation intracoronaire, chez certains patients sélectionnés, qui permettent d’éliminer le substrat et (3)de l’imagerie cardiaque pour mieux identifier le substrat et diminuer les risques perprocédure.La connaissance du substrat spécifique à chaque pathologie, une information sur laforce du contact entre le cathéter et le tissu, l’imagerie cardiaque (scanner et IRM), uneapproche épicardique chez certains patients et l’homogénéisation de la cicatricemyocardique permettent d’être plus efficace lors de l’ablation des TV

An Approach to Catheter Ablation of Cavotricuspid Isthmus Dependent Atrial Flutter

Much of our understanding of the mechanisms of macro re-entrant atrial tachycardia comes from study of cavotricuspid isthmus (CTI) dependent atrial flutter. In the majority of cases, the diagnosis can be made from simple analysis of the surface ECG. Endocardial mapping during tachycardia allows confirmation of the macro re-entrant circuit within the right atrium while, at the same time, permitting curative catheter ablation targeting the critical isthmus of tissue located between the tricuspid annulus and the inferior vena cava. The procedure is short, safe and by demonstration of an electrophysiological endpoint - bidirectional conduction block across the CTI - is associated with an excellent outcome following ablation. It is now fair to say that catheter ablation should be considered as a first line therapy for patients with documented CTI-dependent atrial flutter

Sail trimming FSI simulation - Comparison of viscous and inviscid flow models to optimise upwind sails trim

A numerical comparison between two FSI models, based on inviscid and viscous flow solvers, is presented in this paper. The differences between aerodynamic coefficients, sail flying shape and pressures computed by both FSI tools are investigated for medium wind conditions. These differences are evaluated for different values of the main sheet length. The study has shown very close results when the main sheet is not over trimmed for medium true wind speed, but discrepancies increase when flow separation becomes significant. Then, an optimisation procedure based on inviscid FSI is performed to optimise the main sheet and car trims, in order to maximise an objective function based on the driving and side forces, in a case of low true wind speed. Limitations of the inviscid flow hypothesis are highlighted and the difficulties to use inviscid FSI models in an optimisation procedure, for a case of low true wind speed, are shown

Experimental and numerical optimizations of an upwind mainsail trimming

International audienceThis paper investigates the use of meta-models for optimizing sails trimming. A Gaussian process is used to robustly approximate the dependence of the performance with the trimming parameters to be optimized. The Gaussian process construction uses a limited number of performance observations at carefully selected trimming points, potentially enabling the optimization of complex sail systems with multiple trimming parameters. We test the optimization procedure on the (two parameters) trimming of a scaled IMOCA mainsail in upwind conditions. To assess the robustness of the Gaussian process approach, in particular its sensitivity to error and noise in the performance estimation, we contrast the direct optimization of the physical system with the optimization of its numerical model. For the physical system, the optimization procedure was fed with wind tunnel measurements , while the numerical modeling relied on a fully non-linear Fluid-Structure Interaction solver. The results show a correct agreement of the optimized trimming parameters for the physical and numerical models, despite the inherent errors in the numerical model and the measurement uncertainties. In addition, the number of performance estimations was found to be affordable and comparable in the two cases, demonstrating the effectiveness of the approach

Shortening of Fibrillatory Cycle Length in the Pulmonary Vein During Vagal Excitation

ObjectivesThe goal of the present prospective study is to evaluate the impact of vagal excitation on ongoing atrial fibrillation (AF) during pulmonary vein (PV) isolation.BackgroundThe role of vagal tone in maintenance of AF is controversial in humans.MethodsTwenty-five patients (18 with paroxysmal AF, 7 with chronic AF) were selected by occurrence of vagal excitation during AF (atrioventricular [AV] block: R-R interval >3 s) produced by PV isolation. Fibrillatory cycle length (CL) in the targeted PV and coronary sinus (CS) were determined before, during, and after vagal excitation. The CL was available at PV ostium during vagal excitation in 11 patients.ResultsForty-eight episodes of vagal excitation were observed. During vagal excitation, CL abruptly decreased both in CS and PV (CS, 164 ± 20 ms to 155 ± 23 ms, p < 0.0001; PV, 160 ± 22 ms to 143 ± 28 ms, p < 0.0001), and both returned to the baseline value with resumption of AV conduction. The decrease in PVCL occurred earlier (2.5 ± 1.5 s vs. 4.0 ± 2.6 s, p < 0.01) and was of greater magnitude than that in CSCL (16 ± 16 ms vs. 8 ± 9 ms, p < 0.01). A sequential gradient of CL was observed from PV to PV ostium and CS during vagal excitation (138 ± 29 ms, 149 ± 24 ms, and 159 ± 26 ms, respectively). The decrease in CL was significantly greater in paroxysmal than in chronic AF (CS, 11 ± 9 ms vs. 5 ± 7 ms, p < 0.05; PV, 23 ± 25 ms vs. 8 ± 14 ms, p < 0.05).ConclusionsVagal excitation is associated with shortening of fibrillatory CL. This occurs earlier in PV with a sequential gradient to PV ostium and CS, suggesting that vagal excitation enhances a driving role of PV

Experimental and numerical trimming optimizations for a mainsail in upwind conditions

This paper investigates the use of meta-models for optimizing sails trimming. A Gaussian process is used to robustly approximate the dependence of the performance with the trimming parameters to be optimized. The Gaussian process construction uses a limited number of performance observations at carefully selected trimming points, potentially enabling the optimization of complex sail systems with multiple trimming parameters. We test the optimization procedure on the (two parameters) trimming of a scaled IMOCA mainsail in upwind conditions. To assess the robustness of the Gaussian process approach, in particular its sensitivity to error and noise in the performance estimation, we contrast the direct optimization of the physical system with the optimization of its numerical model. For the physical system, the optimization procedure was fed with wind tunnel measurements, while the numerical modeling relied on a fully non-linear Fluid-Structure Interaction solver. The results show a correct agreement of the optimized trimming parameters for the physical and numerical models, despite the inherent errors in the numerical model and the measurement uncertainties. In addition, the number of performance estimations was found to be affordable and comparable in the two cases, demonstrating the effectiveness of the approach

Fast Personalized Electrophysiological Models from CT Images for Ventricular Tachycardia Ablation Planning

International audienceAims 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 personalised cardiac electrophysiology (EP) model. The simulation output could be useful in the context of post-infarct ventricular tachycardia (VT) radio-frequency ablation (RFA) planning for pre-operative targets prediction

Early Repolarization Syndrome: Diagnostic and Therapeutic Approach

An early repolarization pattern can be observed in 1% up to 13% of the overall population. Whereas, this pattern was associated with a benign outcome for many years, several more recent studies demonstrated an association between early repolarization and sudden cardiac death, so-called early repolarization syndrome. In early repolarization syndrome patients, current imbalances between epi- and endo-cardial layers result in dispersion of de- and repolarization. As a consequence, J waves or ST segment elevations can be observed on these patients' surface ECGs as manifestations of those current imbalances. Whereas, an early repolarization pattern is relatively frequently found on surface ECGs in the overall population, the majority of individuals presenting with an early repolarization pattern will remain asymptomatic and the isolated presence of an early repolarization pattern does not require further intervention. The mismatch between frequently found early repolarization patterns in the overall population, low incidences of sudden cardiac deaths related to early repolarization syndrome, but fatal, grave consequences in affected patients remains a clinical challenge. More precise tools for risk stratification and identification of this minority of patients, who will experience events, remain a clinical need. This review summarizes the epidemiologic, pathophysiologic and diagnostic background and presents therapeutic options of early repolarization syndrome