A paper submitted to The University of Arizona College of Medicine - Phoenix, History of Medicine course.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The Electrocardiograph (EKG or ECG) measures electrical changes of tissue surrounding the heart to create a time-based representation of the physical operation of the heart. The purpose of this paper is to explore the future of ECG telemetry systems and how they are used in health care. The initial goal is to develop an inexpensive, efficient, and robust real-time ECG telemetry system. The future goal is to create a wireless network of miniature body sensors capable of measuring ECG data and other vital signs.

Background: Atrial fibrillation (AF) confers high risk of stroke, but often goes undiagnosed due to difficulties in its diagnosis. AF detection is important in post-stroke populations for secondary prevention and smartwatches have emerged as a promising modality for detecting AF, but little is known about their use in older adults who have experienced a stroke. Methods: This dissertation uses data from the Pulsewatch study, a two-phased trial assessing accuracy, usability, and adherence of smartwatch-based AF detection among older patients after stroke. Analyses performed include: descriptive statistics, linear and logistic regressions, qualitative and mixed-methods analyses, mixed effects modeling, and group-based trajectory modeling. Results: The Pulsewatch system was 91% accurate in detecting AF compared to a clinical gold-standard. Participants found the system easy to use, but indicated that streamlining the smartwatch’s functionalities to focus on passive cardiac monitoring is crucial. Improving battery life to allow for longer wear time would alleviate anxiety in some participants. Participants with previous experience using cardiac rhythm monitors rated the system lower on usability, but overwhelmingly preferred it to previous monitors due to the watch’s comfort, appearance, and convenience. Watch wear decreased over time, and we observed three distinct patterns of decline. No individual-level characteristics were associated with usability or adherence to watch wear. Conclusions: Smartwatches are promising for AF detection in older adults after stroke, though while they offer high accuracy and usability, adherence to wear is low. Strategies to encourage extended watch wear are necessary to realize the potential of smartwatches as a viable cardiac monitoring modality.

The electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. The 12-lead ECG shows this activity in 12 "views" called "leads", relative to the location of sensors attached to the body surface. The ECG is a routinely applied cost effective diagnostic medical test, utilised in healthcare settings around the world. Although more than three hundred million ECGs are recorded each year, correctly interpreting them is considered a complex task. Failure to make correct interpretations can lead to injury or death and costs vast sums in litigation payments. Many automated attempts at interpreting ECGs have been implemented and continue to be developed and improved. Despite this, automated methods are still considered to be less reliable than expert human interpretation. As ECG interpretation is both a cognitive and visual task, eye-tracking holds great potential as an investigative methodology. This thesis aims to identify any cues in visual behaviour that may indicate differences in subsequent ECG interpretation accuracy. This is the first work that uses eye-tracking to analyse how practitioners interpret ECGs as a function of accuracy. In order to investigate these phenomenon, several experiments were carried out using eye-movements captured from clinical practitioners that interpret ECGs as part of their usual clinical role. The findings presented in this thesis have advanced research in the understanding of ECG interpretation. Specifically: Clinical history makes a difference to how people look at ECGs; different gaze patterns are often found in accurate and inaccurate interpretation groups. Grouping data to account for within ECG lead behaviour (eye-movement patterns within a lead) is more revealing than analysis at the level of the lead (eye-movements between leads). Findings suggest analysing visual behaviour at this level is crucial in order to detect behaviour in ECG interpretation. Further to this the thesis presents eye-tracking techniques that can be applied to wider areas of task performance. These methods work over complex stimuli, are able to deal post hoc with differently sized groups and generate appropriate areas of interest on a stimulus. These methods detect important differences in eye-movement behaviour between groups that are missed when applying standard inferential statistical techniques.

This work deals with the classification of cardiac cycles, which uses a method of dynamic time warping and cluster analysis. Method of dynamic time warping is among the elderly, but for its simplicity compared to others is still very much used, and also achieved good results in practice. Cluster analysis is used in many fields such as marketing or just for biological signals. The aim of this work is a general introduction to the ECG signal and the method and implementation of dynamic time warping algorithm. Subsequently, cluster analysis and finally the creation of the user interface for the algorithms.

No description available.

De nos jours, les mesures sans contact du signal cardiaque du patient en utilisant le radar Doppler a suscité un intérêt considérable chez les chercheurs, surtout que les électrocardiographes traditionnels avec des électrodes fixes ne sont pas pratiques dans certains cas comme les nourrissons ou les victimes de brûlure. En raison de la sensibilité des micro­ondes à de petits mouvements, le radar a été utilisé comme système de surveillance de l'activité cardio-pulmonaire humaine. Selon l'effet Doppler, un signal de fréquence constante est transmis vers la cible ayant un déplacement variable puis réfléchi. Le signal réfléchit possède une variation de phase par rapport au temps. Dans notre cas, la cible est la poitrine du patient; Le signal réfléchi de la poitrine de la personne contient le signal cardiorespiratoire. Le système est basé sur un analyseur de réseau vectoriel et deux antennes cornet. Le S21 est calculé en utilisant un analyseur de réseau. La variation de phase de S21 contient des informations de l'activité cardio-pulmonaire. Des techniques de traitement sont utilisées pour extraire le signal cardiaque de la variation de la phase de S21 . Cette thèse présente une étude comparative dans la détection des signaux de battements cardiaques au niveau de la puissance rayonnée et de la fréquence opérationnelle. Les puissances rayonnées sont comprises entre 3 et -17 dBm et les fréquences opérationnelles utilisées sont 2.4, 5.8, 1 0 et 20 GHz. Cela permet de spécifier la fréquence opérationnelle optimale, qui donne un compromis entre la puissance minimale émise ainsi que la complexité du système de mesure. De plus, une étude comparative entre plusieurs méthodes de traitement de signal est proposée pour extraire la meilleure méthode qui permet de mesurer le signal cardiaque et par suite extraire ses paramètres. Des techniques de traitement basées sur des transformées en ondelettes ou le filtrage classique sont présentées et utilisées afin de faire une comparaison entre elles. Le paramètre extrait dans cette thèse est le taux des battements cardiaques. Les mesures ont été effectuées simultanément avec un électrocardiographe afin de valider les mesures du signal cardiaque. Puisque la personne peut se déplacer d'une pièce à une autre à l'intérieur de son domicile, des mesures des quatre côtés de la personne et derrière un mur sont réalisées. Ajoutons une approche de modélisation fondée sur la mesure cardio-respiratoire pour une personne qui exerce une marche en avant. De plus, une comparaison entre un système à micro-ondes à simple et deux antennes pour une personne qui prend son souffle est effectuée afin de tester la précision du système à antenne unique par rapport au a la deuxième. Par suite, des mesures sont effectuées pour une personne qui respire en utilisant un système à une seule antenne. / Nowadays, contact-less monitoring patient's heartbeat using Doppler radar has attracted considerable interest of researchers, especially when the traditional electrocardiogram (ECG) measurements with fixed electrodes is not practical in some cases like infants at risk or sudden infant syndrome or burn victims. Due to the microwave sensitivity toward tiny movements, radar has been employed as a noninvasive monitoring system of human cardiopulmonary activity. According to Doppler effect, a constant frequency signal reflected off an object having a varying displacement will result in a reflected signal, but with a time varying phase. In our case, the object is the patient's chest; the reflected signal of the person's chest contains information about the heartbeat and respiration. The system is based on a vector network analyzer and 2 horn antennas. The S21 is computed using a vector network analyzer. The phase variation of S21 contains information about cardiopulmonary activity. Processing techniques are used to extract the heartbeat signal from the S21 phase. This thesis presents a comparative study in heartbeat detection, considering different radiated powers and frequencies. The radiated powers used are between 3 and -17 dBm and the operational frequencies used are 2.4, 5.8, 10 and 20 GHz. This helps to make a compromise between the minimum power emitted and the complexity of the measurement system. In addition, a comparative study of several signal processing methods is proposed to extract the best technique for heartbeat measurement and thus to extract its parameters. Processing techniques are based on wavelet transforms and conventional filtering in order to make a comparison between them. The parameter extracted in this thesis is the heartbeat rate HR. Measurements were performed simultaneously with a PC-based electrocardiograph to validate the heartbeat rate measurement. Since the person can move from a room to another inside his home, measurements from the four sides of the person and behind a wall are performed. In addition, a modeling approach based on cardio-respiratory measurement for a person who is walking forward is presented. Furthermore, a comparison between single and two-antenna microwave systems for a non-breathing person is carried out to test the accuracy of the single-antenna system relative to the two ­antenna microwave system. After that, measurements are performed using one antenna microwave system for a person who breathes normally.

[pt] Com a motivação de contribuir para a garantia da confiabilidade metrológica de eletrocardiógrafos, o presente trabalho tem por objetivo desenvolver um sistema para avaliação da conformidade de ECGs com base na norma IEC 60601-2-51 e na Recomendação R90 (1990) da OIML. Desde 1995, as normas da série IEC 60601 vêm sendo utilizadas como base para regulamentar a avaliação de equipamentos eletromédicos no País. Em 2003, a IEC publicou a norma IEC 60601-2-51 (avaliação de desempenho de eletrocardiógrafos - ECGs) sendo adotada pela ABNT em 2005, com a denominação ABNT NBR IEC 60601-2-51. O sistema desenvolvido foi estruturado em dois subsistemas: subsistema de avaliação de segurança elétrica e subsistema de avaliação de desempenho. O sistema permite avaliar eletrocardiógrafos analógicos e eletrocardiógrafos digitais sem automatização da medição, de acordo com a norma IEC 60601-2-51. Para avaliar o sistema desenvolvido foram utilizados dois ECGs digitais em uso em hospital público do Rio de Janeiro. A sua calibração, com rastreabilidade ao SI, foi realizada no Laboratório de Metrologia do Parque de Material de Eletrônica da Aeronáutica do Rio de Janeiro (PAME-RJ). Os ensaios realizados mostraram que o sistema atende aos requisitos da norma ABNT NBR IEC 60601-2-51, com limitações caracterizadas no trabalho e passíveis de solução (rejeição de modo comum, deriva com a temperatura e reticulado de tempo e amplitude). / [en] Motivated to contribute with the guarantee of metrological reliability of electrocardiographs, the present work aims at developing a system for conformity assessment of ECGs, based on the IEC 60601-2-51 standard and on the Metrological Recomendation R-90 (1990) of OIML. Since 1995, the standard series IEC 60601 have been used as base to regulate the evaluation of electromedical equipments in Brazil. The IEC 60601-2-51 standard (performance evaluation of electrocardiographs - ECGs) has been published by IEC in 2003 and incorporated by ABNT in 2005, with the denomination ABNT NBR IEC 60601-2-51. To allow the conformity analysis to the applicable standards, the proposed system was structured in two subsystems: subsystem for electric safety evaluation and subsystem for performance evaluation. The system allows to evaluate analogical and digital electrocardiographs without automated measurements, in agreement with the IEC 60601-2- 51 standard. In order to evaluate the system, it was applied on two digital ECGs in use at a public hospital of Rio de Janeiro. Its calibration, with traceability to SI, has been performed at the Metrology Laboratory of the Electronics Material Depot of the Air Force at Rio de Janeiro (PAME-RJ). The tests performed have shown that the system complies with the requirements of the IEC 60601-2-51 standard. The detected limitations, which were characterized in this work, have simple solutions, concerning the common-mode rejection ratio, temperature drift and reticulate of time and amplitude.

This work is dedicated to study of the recognition and classification of cardiac disease, diagnosised through the electrocardiogram ECG. This examination is normally used in heart medical center, emergency, intensive therapy, and with complement diagnosis in heart disease as: acute myocardium infarction, bundle block branches, hypertrophy and others. The software was developed for support to the model, with focus on extraction of ECG signal characteristics, and an artificial neural network for recognition of diseases. For extraction these characteristics, we have used a auto-regressive model, AR, with the algorithm least mean square LMS, to minimize the minimum error. The neural network, with architecture multilayer perceptron and back propagation algorithm of training, was chosen for the recognition of the standards. The method was showed efficient. / Este trabalho dedica-se ao estudo do reconhecimento e classificação de cardiopatias, diagnosticadas através do exame de eletrocardiografia, ECG. Esse exame é comumente utilizado em visitas a cardiologistas, centros de emergência, centros de terapia intensiva e exames eletivos para auxílio de diagnóstico de cardiopatias como: infarto agudo do miocárdio, bloqueios de ramos, hipertrofia e outros. O aplicativo desenvolvido para apoio ao trabalho focaliza a extração de características do sinal ECG, representado por ciclos e a aplicação destas características a uma rede neural artificial para reconhecimento das cardiopatias. Para extração das características do sinal, utilizamos o modelo matemático de previsão de comportamento de curvas, chamado de auto-regressivo, AR, onde utilizamos o passado histórico recente da curva para determinar o próximo ponto; em nosso caso, utilizamos o algoritmo dos mínimos quadrados para adequação do erro, conhecido como LMS. A rede neural de topologia perceptron multicamadas e com algoritmo de treinamento backpropagation foi escolhida para o reconhecimento dos padrões, pela sua capacidade de generalização. O método se mostrou adequado e eficiente ao objetivo proposto. / Mestre em Ciências