Complexity of Atrial Fibrillation Electrograms Through Nonlinear Signal Analysis: In Silico Approach

Identification of atrial fibrillation (AF) mechanisms could improve the rate of ablation success. However, the incomplete understanding of those mechanisms makes difficult the decision of targeting sites for ablation. This work is focused on the importance of EGM analysis for detecting and modulating rotors to guide ablation procedures and improve its outcomes. Virtual atrial models are used to show how nonlinear measures can be used to generate electroanatomical maps to detect critical sites in AF. A description of the atrial cell mathematical models, and the procedure of coupling them within two‐dimensional and three‐dimensional virtual atrial models in order to simulate arrhythmogenic mechanisms, is given. Mathematical modeling of unipolar and bipolar electrogramas (EGM) is introduced. It follows a discussion of EGM signal processing. Nonlinear descriptors, such as approximate entropy and multifractal analysis, are used to study the dynamical behavior of EGM signals, which are not well described by a linear law. Our results evince that nonlinear analysis of EGM can provide information about the dynamics of rotors and other mechanisms of AF. Furthermore, these fibrillatory patterns can be simulated using virtual models. The combination of features using machine learning tools can be used for identifying arrhythmogenic sources of AF

Atrial fibrillation detection in PPG signal recorded through a wristband device

LAUREA MAGISTRAL

Non-invasive predictors of mortality after acute myocardial infarction

AbstractThere is a need to identify patients with an increased risk of dying after acute myocardial infarction (AMI), because sudden cardiac death (SCD) and potentially fatal ventricular tachyarrhythmias can be prevented by an implantable cardioverter-defibrillator, or in some cases, with aggressively optimized drug or revascularization therapy. The present study was designed to study the predictive power of non-invasive risk markers and all-cause, cardiac and arrhythmic mortality in 700 consecutive post-AMI patients discharged alive with optimal medication according to contemporary guidelines.Detrended fluctuation analysis of heart rate variability (HRV) predicted all-cause mortality beyond clinical variables as well as left ventricular function in post-AMI patients. The predictive power of the short-term scaling exponent α₁ was higher than that of the traditional indexes of HRV (for α₁ The presence of sustained T-wave alternans during a predischarge exercise test after AMI was not a marker of mortality. However, the inability to perform an exercise test or to reach the heart rate of 105 beats/min predicted independently all-cause (RR 9.3, 95% CI 2.0–43.3, p SCDs occurred mainly more than 18 months after AMI, and the proportion of SCD was less than 40% of all cardiac deaths. Common arrhythmia markers such as the presence of ventricular premature beats or episodes of nonsustained ventricular tachycardia during ambulatory recordings, the time domain parameters of HRV, baroreflex sensitivity, QT dispersion and QRS complex duration provided only limited predictive power on the risk of SCD or arrhythmic events in patients with optimized beta-blocking therapy. Many risk variables previously considered to predict SCD were better predictors of non-SCD than SCD.Conclusions: 1. The epidemiological pattern of SCD was different from that reported previously. 2. Many arrhythmia risk markers provided only limited information on the risk of SCD. 3. Short-term fractal scaling exponent α₁ provided potentially useful information on the risk for all-cause mortality, and BNP was useful in predicting the risk of SCD in a post-AMI population with optimized therapy.Academic Dissertation to be presented with the assent of the Faculty of Medicine, University of Oulu, for public discussion in the Auditorium 10 of the University Hospital of Oulu, on May 3rd, 2003, at 12 noon.Abstract There is a need to identify patients with an increased risk of dying after acute myocardial infarction (AMI), because sudden cardiac death (SCD) and potentially fatal ventricular tachyarrhythmias can be prevented by an implantable cardioverter-defibrillator, or in some cases, with aggressively optimized drug or revascularization therapy. The present study was designed to study the predictive power of non-invasive risk markers and all-cause, cardiac and arrhythmic mortality in 700 consecutive post-AMI patients discharged alive with optimal medication according to contemporary guidelines. Detrended fluctuation analysis of heart rate variability (HRV) predicted all-cause mortality beyond clinical variables as well as left ventricular function in post-AMI patients. The predictive power of the short-term scaling exponent α₁ was higher than that of the traditional indexes of HRV (for α₁ < 0.65, the risk ratio (RR) in multivariate analysis was 5.1, with 95% confidence intervals (CI) 2.9–8.9; p < 0.001). HRV results from a conventional 24-hour electrocardiographic (ECG) recording system differed significantly when compared to a system with a higher sampling frequency. The difference was generally more pronounced in post-AMI patients than in healthy subjects. The presence of sustained T-wave alternans during a predischarge exercise test after AMI was not a marker of mortality. However, the inability to perform an exercise test or to reach the heart rate of 105 beats/min predicted independently all-cause (RR 9.3, 95% CI 2.0–43.3, p < 0.01) and cardiac mortality (RR 11.1, 95% CI 2.4–50.8, p < 0.01). High levels of natriuretic peptides were associated with both sudden and non-sudden cardiac mortality. B-type natriuretic peptide provided more specific independent information on the risk for subsequent SCD (RR 3.9, 95% CI 1.2–12.3, p < 0.05) than non-SCD. SCDs occurred mainly more than 18 months after AMI, and the proportion of SCD was less than 40% of all cardiac deaths. Common arrhythmia markers such as the presence of ventricular premature beats or episodes of nonsustained ventricular tachycardia during ambulatory recordings, the time domain parameters of HRV, baroreflex sensitivity, QT dispersion and QRS complex duration provided only limited predictive power on the risk of SCD or arrhythmic events in patients with optimized beta-blocking therapy. Many risk variables previously considered to predict SCD were better predictors of non-SCD than SCD. Conclusions: 1. The epidemiological pattern of SCD was different from that reported previously. 2. Many arrhythmia risk markers provided only limited information on the risk of SCD. 3. Short-term fractal scaling exponent α₁ provided potentially useful information on the risk for all-cause mortality, and BNP was useful in predicting the risk of SCD in a post-AMI population with optimized therapy

Novel approaches for quantitative electrogram analysis for rotor identification: Implications for ablation in patients with atrial fibrillation

University of Minnesota Ph.D. dissertation. May 2017. Major: Biomedical Engineering. Advisor: Elena Tolkacheva. 1 computer file (PDF); xxviii, 349 pages + 4 audio/video filesAtrial fibrillation (AF) is the most common sustained cardiac arrhythmia that causes stroke affecting more than 2.3 million people in the US. Catheter ablation with pulmonary vein isolation (PVI) to terminate AF is successful for paroxysmal AF but suffers limitations with persistent AF patients as current mapping methods cannot identify AF active substrates outside of PVI region. Recent evidences in the mechanistic understating of AF pathophysiology suggest that ectopic activity, localized re-entrant circuit with fibrillatory propagation and multiple circuit re-entries may all be involved in human AF. Accordingly, the hypothesis that rotor is an underlying AF mechanism is compatible with both the presence of focal discharges and multiple wavelets. Rotors are stable electrical sources which have characteristic spiral waves like appearance with a pivot point surrounded by peripheral region. Targeted ablation at the rotor pivot points in several animal studies have demonstrated efficacy in terminating AF. The objective of this dissertation was to develop robust spatiotemporal mapping techniques that can fully capture the intrinsic dynamics of the non-stationary time series intracardiac electrogram signal to accurately identify the rotor pivot zones that may cause and maintain AF. In this thesis, four time domain approaches namely multiscale entropy (MSE) recurrence period density entropy (RPDE), kurtosis and intrinsic mode function (IMF) complexity index and one frequency domain approach namely multiscale frequency (MSF) was proposed and developed for accurate identification of rotor pivot points. The novel approaches were validated using optical mapping data with induced ventricular arrhythmia in ex-vivo isolated rabbit heart with single, double and meandering rotors (including numerically simulated data). The results demonstrated the efficacy of the novel approaches in accurate identification of rotor pivot point. The chaotic nature of rotor pivot point resulted in higher complexity measured by MSE, RPDE, kurtosis, IMF and MSF compared to the stable rotor periphery that enabled its accurate identification. Additionally, the feasibility of using conventional catheter mapping system to generate patient specific 3D maps for intraprocedural guidance for catheter ablation using these novel approaches was demonstrated with 1055 intracardiac electrograms obtained from both atria’s in a persistent AF patient. Notably, the 3D maps did not provide any clinically significant information on rotor pivot point identification or the presence of rotors themselves. Validation of these novel approaches is required in large datasets with paroxysmal and persistent AF patients to evaluate their clinical utility in rotor identification as potential targets for AF ablation

Diagnostic Challenges in Sports Cardiology

The foundations of sports cardiology include promoting physical activity and providing a safe environment for training and competition for all athletes at all levels, from professional to recreational. To combine these two aims, reliable tools to perform preparticipation screenings are needed. Moreover, those at high risk of potentially life-threatening events should be advised to limit their training load, while others should be reassured that there is no exercise-related cardiovascular risk. We are currently witnessing the advent of new portable devices for remote and mobile heart monitoring and several new and promising biochemical markers, which can support athletes’ diagnostic processes. In this Special Issue of the Diagnostics journal entitled “Diagnostic Challenges in Sports Cardiology”, we present a series of 13 manuscripts, including eight original works, three reviews, and two case reports, which give a glimpse into the current research topics in the area of sports cardiology

Cardiac Arrhythmogenesis in Urban Air Pollution: Optical Mapping in Tissue-Engineered Model

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Libro de actas. XXXV Congreso Anual de la Sociedad Española de Ingeniería Biomédica

596 p.CASEIB2017 vuelve a ser el foro de referencia a nivel nacional para el intercambio científico de conocimiento, experiencias y promoción de la I D i en Ingeniería Biomédica. Un punto de encuentro de científicos, profesionales de la industria, ingenieros biomédicos y profesionales clínicos interesados en las últimas novedades en investigación, educación y aplicación industrial y clínica de la ingeniería biomédica. En la presente edición, más de 160 trabajos de alto nivel científico serán presentados en áreas relevantes de la ingeniería biomédica, tales como: procesado de señal e imagen, instrumentación biomédica, telemedicina, modelado de sistemas biomédicos, sistemas inteligentes y sensores, robótica, planificación y simulación quirúrgica, biofotónica y biomateriales. Cabe destacar las sesiones dedicadas a la competición por el Premio José María Ferrero Corral, y la sesión de competición de alumnos de Grado en Ingeniería biomédica, que persiguen fomentar la participación de jóvenes estudiantes e investigadores