Microcanonical processing methodology for ECG and intracardial potential: application to atrial fibrillation

Cardiac diseases are the principal cause of human morbidity and mortality in the western world. The electric potential of the heart is a highly complex signal emerging as a result of nontrivial flow conduction, hierarchical structuring and multiple regulation mechanisms. Its proper accurate analysis becomes of crucial importance in order to detect and treat arrhythmias or other abnormal dynamics that could lead to life-threatening conditions. To achieve this, advanced nonlinear processing methods are needed: one example here is the case of recent advances in the Microcanonical Multiscale Formalism. The aim of the present paper is to recapitulate those advances and extend the analyses performed, specially looking at the case of atrial fibrillation. We show that both ECG and intracardial potential signals can be described in a model-free way as a fast dynamics combined with a slow dynamics. Sharp differences in the key parameters of the fast dynamics appear in different regimes of transition between atrial fibrillation and healthy cases. Therefore, this type of analysis could be used for automated early warning, also in the treatment of atrial fibrillation particularly to guide radiofrequency ablation procedures.Comment: Transactions on Mass-Data Analysis of Images and Signals 4, 1 (2012). Accepte

Attenuation of stretch-induced arrhythmias following chemical ablation of Purkinje fibres, in isolated rabbit hearts

Purkinje fibres (PFs) play an important role in some ventricular arrhythmias and acute ventricular stretch can evoke mechanically-induced arrhythmias. We tested whether Purkinje fibres, play a role in these arrhythmias. Pseudo-ECGs were recorded in isolated, Langendorff-perfused, rabbit hearts in which the left ventricular endocardial surface was also irrigated with Tyrode, via an indwelling catheter placed in the left ventricular lumen. The number and period of ectopic activations was measured during left ventricular lumen inflation via an indwelling fluid-filled balloon (500 μL added over 2 s and maintained for 15 s in total). Mechanically-induced arrhythmias occurred in 70% of balloon inflations: they were maximal in the first 5 s and ceased within 15 s. Brief, (10 s) irrigation of the left ventricular lumen with Lugol solution (IK/I2), via the indwelling catheter, reduced inflation-induced ectopics by 98% (p < 0.05). Ablation of endocardial PFs by Lugol was confirmed by Triphenyltetrazolium Chloride staining. Optical mapping revealed the left ventricular epicardial activation patterns of ectopics could have PF-mediated and focal sources. In silico modelling predicted ectopic sources originating in the endocardial region propagate to and through the Purkinje fibres network. Acute distention-induced ectopics are multi-focal, their attenuation by Lugol, their activation patterns and in silico modelling indicate a participation of Purkinje fibres in these arrhythmias

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

A Singularity-analysis Approach to characterize Epicardial Electric Potential

International audienceThe cardiac electrical activity conforms a complex sys- tem, for which nonlinear signal-processing is required to characterize it properly. In this context, an analysis in terms of singularity exponents is shown to provide compact and meaningful descriptors of the structure and dynam- ics. In particular, singularity components reconstruct the epicardial electric potential maps of human atria, inverse- mapped from surface potentials; such approach describe sinus-rhythm dynamics as well as atrial flutter and atrial fibrillation. We present several example cases in which the key descriptors in the form of fast-slow dynamics point at the arrhythmogenic areas in the atria

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

Background: 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.Methods: 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.Results: 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 (p = 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, p < 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, p < 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, p < 0.01), shorter procedures (<30 min: 0.09 ± 0.04 vs. ≥30 min: 0.11 ± 0.03, p < 0.001) and fewer ablation targets (<4: 0.09 ± 0.03 vs. ≥4: 0.11 ± 0.04, p < 0.01).Conclusions: AF complexity can be noninvasively quantified by PCA in BSPMs and correlates with ablation outcome and AF pathophysiology

A new ECG-based method to guide catheter ablation of ventricular tachycardia

International audienceINTRODUCTION Catheter ablation is used to treat ventricular tachycardia (VT). It uses radiofrequency energy to destroy a small part of heart tissue that is causing rapid and irregular heartbeats. Automated localization of VT exit sites can facilitate the long and often challenging ablation procedures but current methods are not accurate enough, cannot be used in some conditions, and often require detailed information about the patient's anatomy. The aim of this study was to optimize the accuracy of a previously proposed computer-based method for localization of arrhythmia exit sites. The effectiveness of the method was tested using simulated ECG data. We looked for optimal settings of the method allowing to apply it in clinical conditions.METHODS The proposed algorithm works on any set of 3 or more ECG leads. The QRS complex integral (QRSi) of an ectopic beat is reduced to principal components (PCs) treated as coordinates of the exit site in ECG space and then projected to real space by a linear transformation based on a small number of QRSis paced at known locations. The accuracy of the method was tested on 8 patient-tailored models of the human heart and torso. For each model ~500 simulations were run, each for a different stimulus location. A set of training points was randomly chosen and all other locations were then estimated from simulated surface ECGs. The absolute and relative (to a neighboring stimulation site) localization errors (in mm) were computed for a 252-lead ECG, and Frank VCG and using different numbers of training points and principal components.RESULTS The localization error depended on the size of the training set. By using patient’s mean transform matrix of stimulus position from ECG space to real space and Frank XYZ leads we found 15.5 ± 6.4 mm of mean absolute error. Starting from 9 pacing positions available and 3 PCs used we reached a similar level of mean error (15.22 ± 3.5 mm). With 20 stimulus points available and 7 PCs we got 10 ± 2 mm of error. Added noise had no significant influence on the results; even a 2 dB signal/noise ratio increased the error by only 1 mm.DISCUSSION This study suggests that the proposed method can predict exit sites with a precision in the order of a centimeter. By dynamically switching the settings of the algorithm it is possible to obtain better accuracy

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

In-Silico Data Based Machine Learning Technique Predicts Premature Ventricular Contraction Origin Coordinates

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A Patient-Specific Equivalent Dipole Model

International audienceSophisticated models for the electrocardiographic inverse problem are available, but their reliance on imaging data and large numbers of electrodes limit their use. Simple models such as the equivalent dipole model (EDM) therefore remain relevant. We developed a probabilistic approach to the equivalent unbounded uniform single dipole problem and developed a natural extension to the bounded nonuniform case that relies on a patientspecific statistical inference of the propagation mechanism between the location of the dipole and the electrode locations. The two models were tested on data simulated with a detailed heart-torso model with four different activation sequences and three different sets of tissue characteristics. We observed a throughout enhancement of the ability to reconstruct the ECG of the patient-specific model when compared to the uniform unbounded dipole model