Data-Driven ECG Denoising Techniques for Characterising Bipolar Lead Sets along the Left Arm in Wearable Long-Term Heart Rhythm Monitoring

Abnormal heart rhythms (arrhythmias) are a major cause of cardiovascular disease and death in Europe. Sudden cardiac death accounts for 50% of cardiac mortality in developed countries; ventricular tachycardia or ventricular fibrillation is the most common underlying arrhythmia. In the ambulatory population, atrial fibrillation is the most common arrhythmia and is associated with an increased risk of stroke and heart failure, particularly in an aging population. Early detection of arrhythmias allows appropriate intervention, reducing disability and death. However, in the early stages of disease arrhythmias may be transient, lasting only a few seconds, and are thus difficult to detect. This work addresses the problem of extracting the far-field heart electrogram signal from noise components, as recorded in bipolar leads along the left arm, using a data driven ECG (electrocardiogram) denoising algorithm based on ensemble empirical mode decomposition (EEMD) methods to enable continuous non-invasive monitoring of heart rhythm for long periods of time using a wrist or arm wearable device with advanced biopotential sensors. Performance assessment against a control denoising method of signal averaging (SA) was implemented in a pilot study with 34 clinical cases. EEMD was found to be a reliable, low latency, data-driven denoising technique with respect to the control SA method, achieving signal-to-noise ratio (SNR) enhancement to a standard closer to the SA control method, particularly on the upper arm-ECG bipolar leads. Furthermore, the SNR performance of the EEMD was improved when assisted with an FFT (fast Fourier transform ) thresholding algorithm (EEMD-fft)

Non-invasive evaluation of ventricular refractoriness and its dispersion during ventricular fibrillation in patients with implantable cardioverter defibrillator

BACKGROUND: Local ventricular refractoriness and its dispersion during ventricular fibrillation (VF) have not been well evaluated, due to methodological difficulties. METHODS: In this study, a non-invasive method was used in evaluation of local ventricular refractoriness and its dispersion during induced VF in 11 patients with VF and/or polymorphic ventricular tachycardia (VT) who have implanted an implantable cardioverter defibrillator (ICD). Bipolar electrograms were simultaneously recorded from the lower oesophagus behind the posterior left ventricle (LV) via an oesophageal electrode and from the right ventricular (RV) apex via telemetry from the implanted ICD. VF intervals were used as an estimate of the ventricular effective refractory period (VERP). In 6 patients, VERP was also measured during sinus rhythm at the RV apex and outflow tract (RVOT) using conventional extra stimulus technique. RESULTS: Electrograms recorded from the RV apex and the lower esophagus behind the posterior LV manifested distinct differences of the local ventricular activities. The estimated VERPs during induced VF in the RV apex were significantly shorter than that measured during sinus rhythm using extra stimulus technique. The maximal dispersion of the estimated VERPs during induced VF between the RV apex and posterior LV was that of 10 percentile VF interval (40 ± 27 ms), that is markedly greater than the previously reported dispersion of ventricular repolarization without malignant ventricular arrhythmias (30–36 ms). CONCLUSIONS: This study verified the feasibility of recording local ventricular activities via oesophageal electrode and via telemetry from an implanted ICD and the usefulness of VF intervals obtained using this non-invasive technique in evaluation of the dispersion of refractoriness in patients with ICD implantation

Martin Hartmann's letter to Ignaz Goldziher

There are contrasting views as to whether education systems and curricular characteristics are converging. A number of theoretical perspectives have been proposed attempting to explain or predict similarities and differences in education systems and curricula around the world, e.g. World Culture theory, and the modernisation and qualitative differences perspectives. From an empirical point of view, existing research investigating variation in citizenship education across countries tends to focus on superficial features such as curriculum objectives and structure, and school subject categories. The more substantive issue of the values and norms promoted in the curriculum are usually ignored because of the difficulty in investigating these. Further, while it is possible to identify convergence at the most general and abstract level, it is at the level of the enactment and implementation of policy that meaningful similarities or differences can be identified. This chapter presents original data at the level of the structural features and curriculum content of citizenship education from 16 Western and East Asian countries. It uses cross-country patterns of the dimensions of state control and collective values to assess the validity and explanatory power of World Culture theory, and the modernisation and qualitative differences perspectives

Introduction and summary

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Control and optimization of dynamical systems in the presence of stochastic uncertainty is a mature field with a large range of applications. A comprehensive treatment of such problems can be found in excellent books and other resources including [7, 16, 29, 68, 84, 95, 104], and [6]. To date, there exist a nearly complete theory regarding the existence and structure of optimal solutions under various formulations as well as computational methods to obtain such optimal solutions for problems with finite state and control spaces. However, there still exist substantial computational challenges involving problems with large state and action spaces, such as standard Borel spaces. For such state and action spaces, obtaining optimal policies is in general computationally infeasible