Ischemia detection from morphological QRS angles changes

In this paper, an ischemia detector is presented based on the analysis of QRS-derived angles. The detector has been developed by modeling ischemic effects on the QRS angles as a gradual change with a certain transition time and assuming a Laplacian additive modeling error contaminating the angle series. Both standard and non-standard leads were used for analysis. Non- standard leads were obtained by applying the PCA technique over specific lead subsets to represent different potential locations of the ischemic zone. The performance of the proposed detector was tested over a population of 79 patients undergoing percutaneous coronary intervention in one of the major coronary arteries (LAD (n = 25), RCA (n = 16) and LCX (n = 38)). The best detection performance, obtained for standard ECG leads, was achieved in the LAD group with values of sensitivity and specificity of Se = 90.9%, Sp = 95.4%, followed by the RCA group with Se = 88.9%, Sp = 94.4 and the LCX group with Se = 86.1%, Sp = 94.4%, notably outperforming detection based on the ST series in all cases, with the same detector structure. The timing of the detected ischemic events ranged from 30 s up to 150 s (mean = 66.8 s) following the start of occlusion. We conclude that changes in the QRS angles can be used to detect acute myocardial ischemi

Progress Report No. 13

Progress report of the Biomedical Computer Laboratory, covering period 1 July 1976 to 30 June 1977

Analyse automatisée du signal électrocardiographique dans les arythmies atriales chez le rat vigil

Atrial fibrillation is the most common cardiac arrhythmia and its pathophysiology is still poorly understood. To date, there is no animal model in which the arrhythmia occurs spontaneously. As ageand hypertension are major risk factors of atrial fibrillation in humans, we examined whether the aging (11-13 months of age) spontaneously hypertensive rat (SHR) develops this pathology. Telemetric recordings of electrocardiogram (ECG) were obtained in four groups of conscious rats. They revealed the presence in the aging SHR of many non-sustained atrial tachyarrhythmic episodes that were observed neither in the young SHR nor in the young or aging normotensive Wistar Kyotorat. These results were obtained by visual examination of the whole ECG recordings, which is extremely time consuming and thus, not compatible with routine experiments. Therefore, we chose to develop an automated method to detect atrial arrhythmias in the conscious rat. This method only uses RR intervalsbecause P waves cannot always be accurately identified in telemetric recordings. It recognizes characteristicpatterns of tachyarrhythmia by using an automaton structure, and shows a good performance when applied to previously collected telemetric data. The new animal model, together with the new, automated method of ECG analysis, are expected to be extremely useful for producing high quality phenotypic data, which are necessary to test present molecular hypotheses of atrial fibrillation pathophysiology.La fibrillation atriale est la plus fréquente des arythmies cardiaques et sa physiopathologie reste mal comprise. Il n’existe pas actuellement de modèle animal dans lequel cette arythmie survienne de manière spontanée. Comme l’âge et l’hypertension artérielle sont deux facteurs de risque majeurs dela fibrillation atriale chez l’Homme, nous avons recherché si le rat spontanément hypertendu (SHR)vieillissant (11-13 mois d’âge) développe cette pathologie. Des enregistrements télémétriques de 24 h de l’électrocardiogramme (ECG) ont été réalisés dans 4 groupes de rats vigils. Ils ont révélé chez le rat SHR vieillissant la présence de nombreux épisodes de tachyarythmie atriale non soutenus, épisodes qui ne sont pas observés chez le rat SHR jeune ni chez lerat normotendu Wistar Kyoto jeune ou vieillissant. Les résultats rapportés ci-dessus ont été obtenus grâce à l’analyse visuelle de l’intégralité de chaque enregistrement ECG, ce qui représente une durée d’analyse incompatible avec des expérimentations de routine. Nous avons donc choisi de développer une méthode automatique de reconnaissance des arythmies atriales chez le rat vigil. Cette méthode utilise exclusivement les intervalles RR car les ondes P ne peuvent pas toujours être identifiées avec fiabilité dans les enregistrements télémétriques de l’ECG. Elle repère les motifs caractéristiques de tachyarythmie grâce à une structure d’automate, et présente une bonne performance sur les enregistrements télémétriques déjà réalisés. Le nouveau modèle animal, conjointement à la nouvelle méthode automatique d’analyse de l’ECG, devrait permettre de réaliser les analyses phénotypiques de qualité indispensables aux hypothèses physiopathologiques moléculaires actuellement avancées dans la fibrillation atriale

Body sensor networks: smart monitoring solutions after reconstructive surgery

Advances in reconstructive surgery are providing treatment options in the face of major trauma and cancer. Body Sensor Networks (BSN) have the potential to offer smart solutions to a range of clinical challenges. The aim of this thesis was to review the current state of the art devices, then develop and apply bespoke technologies developed by the Hamlyn Centre BSN engineering team supported by the EPSRC ESPRIT programme to deliver post-operative monitoring options for patients undergoing reconstructive surgery. A wireless optical sensor was developed to provide a continuous monitoring solution for free tissue transplants (free flaps). By recording backscattered light from 2 different source wavelengths, we were able to estimate the oxygenation of the superficial microvasculature. In a custom-made upper limb pressure cuff model, forearm deoxygenation measured by our sensor and gold standard equipment showed strong correlations, with incremental reductions in response to increased cuff inflation durations. Such a device might allow early detection of flap failure, optimising the likelihood of flap salvage. An ear-worn activity recognition sensor was utilised to provide a platform capable of facilitating objective assessment of functional mobility. This work evolved from an initial feasibility study in a knee replacement cohort, to a larger clinical trial designed to establish a novel mobility score in patients recovering from open tibial fractures (OTF). The Hamlyn Mobility Score (HMS) assesses mobility over 3 activities of daily living: walking, stair climbing, and standing from a chair. Sensor-derived parameters including variation in both temporal and force aspects of gait were validated to measure differences in performance in line with fracture severity, which also matched questionnaire-based assessments. Monitoring the OTF cohort over 12 months with the HMS allowed functional recovery to be profiled in great detail. Further, a novel finding of continued improvements in walking quality after a plateau in walking quantity was demonstrated objectively. The methods described in this thesis provide an opportunity to revamp the recovery paradigm through continuous, objective patient monitoring along with self-directed, personalised rehabilitation strategies, which has the potential to improve both the quality and cost-effectiveness of reconstructive surgery services.Open Acces

Análise remota do eletrocardiograma para detecção de eventos isquêmicos

The evolution of technologies for remote services delivery over the Internet unveils a new frontier in the development of the knowledge needed to implement health prevention measures. In this study, a computational tool was conceived for the remote analysis of multiple lead electrocardiograms. As a proof of concept, a method for detecting ST-T segment changes related to ischemic episodes in remote computing is proposed. The architecture combines only open source software that allows incremental object-oriented programming and support multiuser services via the Web, focusing on system evolution within the academic world. The technique used to detect ischemic events favored low computational cost and storage of both data and metadata in a database. It was anchored in a method of interpolation by weighted least squares and histograms, capable of detecting the positions of the QRS complexes, and the respective positions of J points and T waves. These points were used as borderline positions in obtaining representative under curve areas for the subsequent detection of ischemic events in the leads present in the research file. After assessment with engineering students, we conclude that the platform, architecture, and programming techniques provide a satisfactory tool for ischemic event management that can be used to develop new biomedical signal processing techniques that support the risk assessment of myocardial dysfunction.A evolução das tecnologias para entrega de serviços remotos pela Internet revela uma nova fronteira no desenvolvimento do conhecimento necessário para implementar medidas de prevenção da saúde. Neste estudo, uma ferramenta computacional foi concebida para a análise remota de eletrocardiogramas de múltiplas derivações. Como prova de conceito, um método é proposto para detectar alterações no segmento ST-T relacionadas a episódios isquêmicos através da computação remota. A arquitetura combina apenas software de código aberto que permite programação incremental orientada a objetos e oferece suporte a serviços multiusuário via Web, com foco na evolução do sistema no mundo acadêmico. A técnica utilizada para detectar eventos isquêmicos favoreceu o baixo custo computacional e armazenamento de dados e metadados em um Banco de Dados. Foi ancorado em um método de interpolação por mínimos quadrados ponderados e histogramas, capazes de detectar as posições dos complexos QRS e as respectivas posições dos pontos J e ondas T. Esses pontos foram usadas como posições limítrofes na obtenção de áreas representativas sob curvas para a subsequente detecção de eventos isquêmicos nas derivações presentes no arquivo de pesquisa. Após avaliação junto a discentes de engenharia, concluímos que a plataforma, arquitetura e técnicas de programação fornecem uma ferramenta satisfatória para o gerenciamento de eventos isquêmicos, a qual pode ser usada para o desenvolvimento de novas técnicas de processamento de sinais biomédicos que objetivem apoiar a avaliação de risco de disfunção miocárdic