Until recently, the major portion of the study of the electrical activity of the heart has been done with the aid of electrocardiograms and vectorcardiograms. However, such information as the variation of the magnitude and angle of the heart vector with time is not directly discernible from either of these recordings. A polarcardiograph was developed by W.K.R. Park to present the plane projection of the heart vector in magnitude and angle as a continuous function of time. The polarcardiograph proved to be useful but it was not sufficiently stable. An electronic device which would be stable and at the same-time present the heart vector in three dimensions, magnitude, frontal angle and polar angle as continuous functions of time, would be useful in electrocardiographic research. The design of such a computer, the "spherical polarcardiograph", is described in this thesis. The spherical polarcardiograph, which must compute the spherical polar coordinates of points from their respective Cartesian coordinates, has been developed using analog multipliers, subtracters and adders as well as a two-phase sinusoidal voltage source and a device for generating a voltage proportional to the phase difference of two sinusoidal signals. With the exception of the third coordinate computation and the gated feedback circuitry, the system is similar to that used by Park. Automatic balancing of the circuit occurs for a short interval during the rest period of the heart. The spherical polarcardiograph has not been constructed in final form but tests on the individual units indicate that the instrument will be well within the accuracy required for normal electrocardiographic purposes. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

Heart disease is the leading cause of death globally. Early diagnosis is the key to successful treatment. By providing noninvasive, non-ionizing, and real-time imaging, echocardiography plays a critical role in identifying heart disease. Compared to other imaging modalities, ultrasound has unparalleled temporal resolution. High frame-rate imaging has enabled the development of new metrics to characterize myocardial mechanics. Strain imaging measures the heart's deformation throughout the cardiac cycle, providing a quantitative assessment of cardiac health. The intention of this dissertation is to bring Myocardial Elastography (ME) closer to clinical realization. ME is a high frame-rate strain imaging technique for transthoracic and intracardiac echocardiography. This work consists of four Aims. There is a fundamental trade-off between spatial and temporal resolution in strain imaging. In Aim 1, the optimal transmit sequence that generates the most accurate and precise strain estimate was determined. Two common approaches to coherent compounding (full and partial aperture) were compared in simulation and in transthoracic imaging of healthy human subjects (n=5). The optimized subaperture compounding sequence (25-element subperture, 90° angular aperture, 10 virtual sources, 300 Hz frame rate) was compared to the optimized steered compounding sequence (60° angular aperture, 15° tilt, 10 virtual sources, 300 Hz frame rate) and was found to measure strain in healthy human subjects with equivalent precision. The optimal compounding configuration was then evaluated against two other high-frame rate transmit strategies, ECG-gated focused imaging, and wide-beam imaging, in simulation and in healthy subjects (n=7). Achieving the highest level of strain precision, ECG-gated focused imaging was determined to be the preferred imaging approach in patients capable of sustaining a breath hold, with compounding preferred in those unable to do so. Rapid diagnosis is essential to successful treatment of myocardial infarction. In Aim 2, ME's ability to track infarct formation and recovery, and localize infarct using regional strain measurments, was investigated in a large animal survival model (n=11). Infarcts were generated via ligation of the left anterior descending, imaging regularly for up to 28 days. A radial strain-based metric, percentage of healthy myocardium by strain (PHM_ε), was developed as a marker for healthy myocardial tissue. PHM_ε was strongly linearly correlated with actual infarct size as determined by gross pathology (R2 = 0.80). ME was capable of diagnosing individual myocardial segments as non-infarcted or infarcted with high sensitivity (82%), specificity (92%), and precision (85%) (ROC AUC = 0.90), and tracked infarct recovery from collateral reperfusion through time. Noninvasive strain imaging at rest can improve pre-test probability accuracy, and reduce unnecessary stress testing. In Aim 3, ME's potential to provide early diagnosis of coronary artery disease was investigated in an ongoing study. Patients undergoing myocardial perfusion imaging were recruited (n=126). Perfusion scores were used as the reference standard. Morphological transformations were integrated into the processing pipeline to reduce variability in the strain measurements. PHM_ε was reintroduced and used to differentiate between patients with and without coronary artery disease. ME was capable of distinguishing between normal patients and those with significant ischemia or infarct (subjects with perfusion defects at rest) with statistical significance (p < 0.05), although a greater sample size is needed to confirm the results. One of the most common treatments for arrhythmia, catheter ablation, can fail if the lesion line intended to terminate the abnormal rhythm is non-contiguous. In Aim 4, the gap resolution and clinical feasibility of Intracardiac Myocardial Elastography (IME) strain imaging, an ablation monitoring technique, was investigated. Lesion size estimation and gap resolution was evaluated in an open chest canine model (n=3), wherein lesion lines consisting of three lesions and two gaps were generated in each canine left ventricle via epicardial ablation. All gaps were resolvable. Average lesion and gap areas were measured with high agreement (33 ± 14 mm2 and 30 ± 15 mm2, respectively) when compared against gross pathology (34 ± 19 mm2 and 26 ± 11 mm2, respectively). Gaps as small as 11 mm2 (3.6 mm on epicardial surface) were identifiable. Patients undergoing ablation to treat typical cavotricuspid isthmus atrial flutter (n=5) were imaged throughout the procedure. In all patients, strain decreased in the cavotricuspid isthmus after ablation (mean paired difference of -17 ± 11 %, p < 0.05). Together, these Aims intend to translate a promising imaging method from research to clinical reality.

Lu, Yan. / "October 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 65-68). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Electrocardiogram --- p.1 / Chapter 1.1.1 --- ECG Measurement --- p.2 / Chapter 1.1.2 --- Cardiac Conduction Pathway and ECG Morphology --- p.4 / Chapter 1.1.3 --- A Basic Clinical Approach to ECG Analysis --- p.6 / Chapter 1.2 --- Cardiovascular Disease --- p.7 / Chapter 1.3 --- Motivation --- p.9 / Chapter 1.4 --- Related Work --- p.10 / Chapter 1.5 --- Overview of Proposed Approach --- p.11 / Chapter 1.6 --- Thesis Outline --- p.13 / Chapter 2. --- ECG Signal Preprocessing --- p.14 / Chapter 2.1 --- ECG Model and Its Generalization --- p.14 / Chapter 2.1.1 --- ECG Dynamic Model --- p.14 / Chapter 2.1.2 --- Generalization of ECG Model --- p.15 / Chapter 2.2 --- Empirical Mode Decomposition --- p.17 / Chapter 2.3 --- Baseline Wander Removal --- p.20 / Chapter 2.3.1 --- Sources of Baseline Wander --- p.20 / Chapter 2.3.2 --- Baseline Wander Removal by EMD --- p.20 / Chapter 2.3.3 --- Experiments on Baseline Wander Removal --- p.21 / Chapter 2.4 --- ECG Denoising --- p.24 / Chapter 2.4.1 --- Introduction --- p.24 / Chapter 2.4.2 --- Instantaneous Frequency --- p.26 / Chapter 2.4.3 --- Problem of Direct ECG Denoising by EMD : --- p.28 / Chapter 2.4.4 --- Model-based Pre-filtering --- p.30 / Chapter 2.4.5 --- EMD Denoising Using Significance Test --- p.33 / Chapter 2.4.6 --- EMD Denoising using Instantaneous Frequency --- p.35 / Chapter 2.4.7 --- Experiments --- p.39 / Chapter 2.5 --- Chapter Summary --- p.44 / Chapter 3. --- ECG Classification --- p.45 / Chapter 3.1 --- Database --- p.45 / Chapter 3.2 --- Feature Extraction --- p.46 / Chapter 3.2.1 --- Feature Selection --- p.46 / Chapter 3.2.2 --- Feature Dimension Reduction by GDA --- p.48 / Chapter 3.3 --- Classification by Support Vector Machine --- p.50 / Chapter 3.4 --- Experiments --- p.53 / Chapter 3.4.1 --- Performance of Feature Reduction --- p.54 / Chapter 3.4.2 --- Performance of Classification --- p.57 / Chapter 3.4.3 --- Performance Comparison with Other Works --- p.60 / Chapter 3.5 --- Chapter Summary --- p.61 / Chapter 4. --- Conclusions --- p.63 / Reference --- p.65

published_or_final_version / Community Medicine / Master / Master of Public Health

Heart disease is a major cause of death in western countries. In order to diagnose and monitor heart disease, 3D echocardiography is an important tool, as it provides a fast, relatively low-cost, portable and harmless way of imaging the moving heart. Segmentation of cardiac walls is an indispensable method of obtaining quantitative measures of heart function. However segmentation of ultrasound images has its challenges: image quality is often relatively low and current segmentation methods are often not fast. It is desirable to make the segmentation technique as fast as possible, making quantitative heart function measures available at the time of recording. In this thesis, we test two state-of-the-art fast segmentation techniques to address this issue; furthermore, we develop a novel technique for finding the best segmentation propagation strategy between points of time in a cardiac image sequence. The first fast method is Graph Cuts (GC), an energy minimisation technique that represents the image as a graph. We test this method on static 3D echocardiography to segment the myocardium, varying the importance of the regulariser function. We look at edge measures, position constraints and tissue characterisation and find that GC is relatively fast and accurate. The second fast method is Random Forests (RFos), a discriminative classifier using binary decision trees, used in machine learning. To our knowledge, we are the first to test this method for myocardial segmentation on 2D and 3D static echocardiography. We investigate the number of trees, image features used, some internal parameters, and compare with intensity thresholding. We conclude that RFos are very fast and more accurate than GC segmentation. The static RFo method is subsequently applied to all time frames. We describe a novel optical flow based propagation technique that improves the static results by propagating the results from well-performing time frames to less-performing frames. We describe a learning algorithm that learns for each frame which propagation strategy is best. Furthermore, we look at the influence of the number of images and of the training set available per tree, and we compare against other methods that use motion information. Finally, we perform the same propagation learning method on the static GC results, concluding that the propagation method improves the static results in this case as well. We compare the dynamic GC results with the dynamic RFo results and find that RFos are more accurate and faster than GC.

儘管心力衰竭的診斷和治療已取得了長足進步，但是心力衰竭依然是目前主要的致殘和致死病因。而且，隨著人口的老齡化，心力衰竭的發病率不斷上升。然而心力衰竭的快速診斷、心功能評價以及患者的危險分層依然面臨眾多挑戰。Acoustic cardiography 是一項經濟簡單的新技術。憑藉獨有的雙功能感測器，這項技術可以同時評估收縮間期（systolic time intervals）以及舒張期心音（diastolic heart sounds）。這項技術提供的主要參數包括：第三心音分數（S3 score；第三心音存在的可能性），電機械時間（EMAT, electromechanical activation time；從心電圖Q 波到心音圖第一心音的時間）及電機械時間比例（%EMAT；電機械時間占整個心動週期的比例），收縮障礙指數（SDI, systolic dysfunctionindex）。本論文主要涵蓋Acoustic cardiography 在心力衰竭患者中如下三個方面 的應用： / 一、心力衰竭的診斷和不同亞型的識別 / 本研究入組了 94 名高血壓但無心力衰竭患者、109 名射血分數正常的心力衰竭患者以及89 名射血分數減低的心力衰竭患者，我們發現%EMAT 可以鑒別射血分數正常的心力衰竭和高血壓患者。另一方面，SDI 是鑒別分射血分數正常和射血分數減低患者的最好指標。 / 二、心力衰竭患者心功能障礙嚴重程度評估 / 此研究共招募 94 名高血壓患者和127 名射血分數減低的心力衰竭患者。結果顯示：SDI 可以鑒別射血分數減低的心力衰竭和高血壓患者。亞組分析顯示：SDI 可以區分射血分數嚴重減低和中度減低的心力衰竭患者；S3 score 可以識別伴舒張功能嚴重障礙的心力衰竭患者。 / 三、心力衰竭患者的危險分層 / 共計 474 名心力衰竭患者被納入此研究，平均隨訪時間484±316 天，169名患者死亡，其中125 名死於心臟病。SDI 和S3 score 都是全因死亡率的獨立預測因數；Kaplan Meier 分析顯示：SDI ≥ 5 或S3 score ≥ 4.12 的心力衰竭患者的生存率顯著降低。 / 通過以上三個方面的研究，我們發現這項新技術有助於（1）心力衰竭的診斷和不同亞型的識別；（2）評估心力衰竭患者的心功能障礙嚴重程度，進而發現其中的高危人群；（3）心力衰竭患者的危險分層。因此，這項新技術有望在心力衰竭患者的管理中扮演早期診斷、評估以及危險分層的重要角色。 / Despite recent advances in its management, heart failure remains a major cause of disability and death and its prevalence is still increasing as the population ages. However, rapid and accurate bedside diagnosis, evaluation as well as risk stratification of heart failure still remain challenging. / Acoustic cardiography (AUDICOR, Inovise Medical, Inc., Portland, OR, USA) is a novel and user friendly equipment which can be used in a wide variety of clinical conditions. With proprietary dual-functional sensors, this technology permits simultaneous acquisition of detailed information regarding systolic time intervals and diastolic heart sounds and provides a computerized interpretation of the findings. Major acoustic cardiographic parameters include S3 score (probability that the third heart sound exists), electromechanical activation time (EMAT, interval from Q wave to the first heart sound; %EMAT is the proportion of cardiac cycle that EMAT occupies), and systolic dysfunction index (SDI= exp [S3 score/10] x QRS interval x QR interval x %EMAT).This thesis will cover 3 aspects of clinical application of acoustic cardiography in heart failure patients. / I. Identification of heart failure and its phenotypes / We performed one study involving 94 patients with hypertension without heart failure, 109 patients with heart failure with normal ejection fraction (HFNEF, EF > 50%) and 89 patients with heart failure and reduced ejection fraction (HFREF, EF < 50%). We found that %EMAT significantly differentiated HFNEF from hypertension. Whereas SDI out-performed the other acoustic cardiographic parameters in differentiating HFREF from HFNEF. / II. Assessment of HFREF patients at high risk by evaluating the severity of left ventricular (LV) systolic and diastolic dysfunction / Ninety-four hypertensive patients without heart failure and 127 HFREF patients (EF < 50%) were consecutively recruited for the study. SDI significantly differentiated HFREF from hypertension. In subgroup analysis, SDI discriminated HFREF patients with severely impaired EF (EF ≤ 35%) from those with moderately impaired EF (35% < EF <50%). S3 score > 4.67 identified HFREF patients with restrictive LV filling pattern. / III. Risk stratification in patients with heart failure / A total of 474 patients hospitalized for heart failure were enrolled into our study. During a mean follow-up time of 484±316 days, 169 (35.7%) patients died and 125 (26.4%) of them died of cardiac causes. After controlling for other potential confounders, we found that S3 score ≥ 4.12, and SDI ≥ 5 were both independent predictors for all-cause mortality. Kaplan-Meier analysis showed that heart failure patients with SDI ≥ 5 or S3 score ≥ 4.12 had a significantly lower survival rate than those with lower SDI or S3 score. / In summary, this bedside technology offers a wide variety of clinical applications in (1) identification of heart failure and its phenotypes; (2) assessmet of HFREF patients at high risk by evaluating the severity of LV systolic and diastolic dysfunction; (3) risk stratification in patients with heart failure. Thus, acoustic cardiography is likely to be helpful in the management of heart failure patients, acting as an early detection, evaluation and risk-stratification tool. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wang, Shang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 123-135). / Abstract also in Chinese. / DECLARATION OF ORIGINALITY --- p.i / ACKNOWLEDGEMENTS --- p.ii / PUBLICATIONS RELATED TO THIS THESIS --- p.iv / Full publications --- p.iv / Conference presentations --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF TABLES --- p.xi / LIST OF FIGURES --- p.xiii / LIST OF ABBREVIATIONS --- p.xv / ABSTRACT --- p.xviii / 論文摘要 --- p.xx / Chapter PART I --- LITERATURE REVIEW --- p.1 / Chapter Chapter 1 --- Introduction to Acoustic Cardiography --- p.2 / Chapter 1.1 --- History of auscultation, phonocardiography --- p.2 / Chapter 1.2 --- STIs --- p.3 / Chapter 1.2.1 --- Conventional STIs --- p.3 / Chapter 1.1.2 --- Echocardiographic STI --- p.5 / Chapter 1.3 --- Acoustic cardiography --- p.7 / Chapter 1.3.1 --- ECG parameters of acoustic cardiography --- p.11 / Chapter 1.3.2 --- Systolic parameters of acoustic cardiography --- p.12 / Chapter 1.3.3 --- Diastolic Parameters of acoustic cardiography --- p.13 / Chapter 1.4 --- Comparison between acoustic cardiography and traditional phonocardiography --- p.19 / Chapter Chapter 2 --- Clinical Application of Acoustic Cardiography --- p.27 / Chapter 2.1 --- Mechanism of generation of S3 and S4 --- p.27 / Chapter 2.2 --- Prevalence of S3 and S4 --- p.28 / Chapter 2.3 --- Clinical auscultation of S3 and S4 problems --- p.29 / Chapter 2.4 --- Rapid identification of heart failure or LV dysfunction --- p.32 / Chapter 2.4.1 --- S3 and S4 --- p.32 / Chapter 2.4.2 --- EMAT --- p.33 / Chapter 2.4.3 --- SDI --- p.34 / Chapter 2.4.5 --- Other derived acoustic cardiographic parameters --- p.34 / Chapter 2.5 --- Predicting elevated LV filling pressure --- p.35 / Chapter 2.6 --- Improving diagnostic utility of BNP in detection of heart failure or LV dysfunction --- p.36 / Chapter 2.7 --- Hemodynamic correlations of acoustic cardiographic parameters --- p.37 / Chapter 2.8 --- Prognostic value of acoustic cardiography --- p.38 / Chapter 2.9 --- Cardiac resynchronization therapy --- p.39 / Chapter 2.10 --- Detection of ischemia --- p.40 / Conclusions --- p.42 / Chapter PART II --- STUDIES ON APPLICATION OF ACOUSTIC CARDIOGRAPHY --- p.48 / Chapter Chapter 3 --- Acoustic Cardiography Helps to Identify Heart Failure and Its Phenotypes --- p.49 / Introduction --- p.49 / Methods --- p.50 / Participants and study design --- p.50 / Echocardiography --- p.51 / Acoustic cardiography --- p.52 / Assessment of reproducibility --- p.55 / Statistical analysis --- p.55 / Results --- p.56 / Characteristics of study subjects --- p.56 / Acoustic cardiographic and echocardiographic characteristics --- p.59 / Diagnostic characteristics of acoustic cardiography --- p.64 / Analysis of covariance results --- p.68 / Inter-operator reproducibility --- p.68 / Discussion --- p.68 / Chapter Chapter 4 --- Rapid Bedside Identification of High-Risk Population in Heart Failure with Reduced Ejection Fraction by Acoustic Cardiography --- p.72 / Introduction --- p.72 / Methods --- p.73 / Study population --- p.73 / Echocardiography --- p.73 / Acoustic cardiography --- p.74 / Assessment of reproducibility --- p.74 / Statistical analysis --- p.74 / Results --- p.75 / Baseline characteristics of study subjects --- p.75 / Acoustic cardiographic and echocardiographic characteristics --- p.78 / Diagnostic test characteristics of acoustic cardiography --- p.84 / Analysis of covariance results --- p.89 / Inter-operator reproducibility --- p.89 / Discussion --- p.89 / Chapter Chapter 5 --- Prognostic value of Acoustic Cardiography in Risk Stratification of Patients With Heart Failure --- p.93 / Introduction --- p.93 / Methods --- p.94 / Study population --- p.94 / Acoustic cardiography --- p.94 / Echocardiography --- p.94 / Endpoint --- p.95 / Assessment of reproducibility --- p.95 / Statistical analysis --- p.95 / Results --- p.96 / Study population --- p.96 / All-cause mortality --- p.100 / Cardiac death --- p.100 / Subgroup analysis in 232 patients undergoing echocardiography --- p.107 / Inter-operator reproducibility --- p.107 / Discussion --- p.114 / Strengths and potential limitations --- p.115 / Chapter PART III --- CONCLUSIONS --- p.117 / Chapter Chapter 6 --- Summary of the Present Studies --- p.118 / Chapter I. --- Identification of heart failure and its phenotypes --- p.118 / Chapter II. --- Assessment of HFREF patients at high risk by evaluating the severity of LV systolic and diastolic dysfunction --- p.119 / Chapter III. --- Risk stratification in patients with heart failure --- p.119 / Chapter Chapter 7 --- Future Research Directions --- p.121 / References --- p.123

by Leung Sze-wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 79-84). / Abstracts in English and Chinese. / ACKNOWLEDGEMENT --- p.II / ABSTRACT --- p.III / 摘要 --- p.V / CONTENTS --- p.VI / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Objectives --- p.1 / Chapter 1.2 --- Prevalence of Heart Diseases --- p.1 / Chapter 1.3 --- Importance of ECG Monitoring --- p.2 / Chapter 1.4 --- Wireless Electrode --- p.2 / Chapter 1.5 --- Analogue-to-Digital Converters --- p.3 / Chapter 1.6 --- Organization of Thesis --- p.4 / Chapter CHAPTER 2 --- LITERATURE REVIEW --- p.5 / Chapter 2.1 --- Telemetry --- p.5 / Chapter 2.1.1 --- "Definitions of ""Telemetry “" --- p.5 / Chapter 2.1.2 --- Advantages of Telemetry --- p.6 / Chapter 2.1.3 --- History of Telemetry --- p.7 / Chapter 2.1.4 --- Special Considerations on Telemetry System --- p.10 / Chapter 2.2 --- Sigma-Delta Converter --- p.12 / Chapter 2.2.1 --- Conventional Digitizing Circuitry --- p.12 / Chapter 2.2.2 --- "Single, Dual-Slope A/D Converters" --- p.13 / Single-Slope A/D Converter --- p.13 / Dual-Slope Converter --- p.75 / Chapter 2.2.3 --- Successive Approximation (SAR) --- p.17 / Chapter 2.2.4 --- Flash Converters --- p.18 / Chapter 2.2.5 --- Sigma-Delta Converter --- p.18 / Chapter 2.3 --- Conclusion --- p.20 / Chapter CHAPTER 3 --- WIRELESS ELECTRODE --- p.21 / Chapter 3.1 --- """Single Electrode"" Measurement" --- p.21 / Chapter 3.2 --- VSE (Virtual Single Electrode) --- p.21 / Concentric Electrode --- p.21 / Chapter 3.3 --- WE (Wireless Electrode) --- p.24 / Chapter 3.4 --- Discussion --- p.29 / Chapter CHAPTER 4 --- SIGMA-DELTA CONVERTER FOR ECG SIGNALS --- p.30 / Chapter 4.1 --- Motivations --- p.30 / Chapter 4.2 --- Baseband Application --- p.31 / Chapter 4.2.1 --- Simulation Results --- p.31 / Chapter 4.2.2 --- Experimental Results --- p.48 / Chapter 4.3 --- Wireless Application --- p.58 / Chapter 4.3.1 --- General Description --- p.58 / Chapter 4.3.2 --- Simulation Results --- p.59 / Chapter 4.3.3 --- Scenario 1 (Analogue Decoding) --- p.70 / Chapter 4.3.4 --- Scenario II (Digital Decoding) --- p.73 / Chapter 4.4 --- Discussion and Conclusion --- p.76 / Chapter CHAPTER 5 --- CONCLUSION AND FUTURE WORK --- p.77 / Chapter 5.1 --- General Conclus ion --- p.77 / Chapter 5.2 --- Future Work --- p.78 / BIBLIOGRAPHY --- p.79 / LIST OF ABBREVIATIONS --- p.85

1. An explicit mathematical description of PEP in terms of DBP was proposed, which in the first time quantitatively clarified the ventricular and arterial effects on PEP timing. / 2. A nonlinear pressure-volume relationship which reflected the natural arterial wall properties was introduced into the asymmetric T-tube arterial model, which effectively and quantitatively described the effect of pulsatile BP on arterial parameters, e.g., compliance, PTT etc. / 3. A mathematical relationship between PAT and BP was firstly proposed as a result of the heart-arterial interaction, which simulated a significantly strong and negative relationship between PAT and SBP and between PAT and MBP but a much weaker negative relationship between PAT and DBP during exercise. The hypothesis was supported by the experiment data. To our knowledge, it is the first study describing the quantitative relation of PAT and BP by both model-based study and experimental data. / 4. A novel wearable measurable CO parameter, PTRR, was proposed and it successfully showed a significantly high and positive correlation with CO during exercise both in model simulation and in the experiments. / 5. Linear prediction models using PAT to estimate MBP and using PTRR to estimate CO were proposed and evaluated in two exercise experiments conducted on 84 subjects with different ages and cardiovascular diseases. Results showed the proposed method could achieve the accuracy required for medical diagnosis. / 6. Taken the findings in 3, 4 and 5 together, this study in the first time provided both the theoretical basis and experimental verifications of developing a wearable and direct measurement technique of CPO in dynamic exercise using multiple physiological signals measured on body surface. / Cardiac power output (CPO) is defmed as the product of mean arterial blood pressure (MBP) and cardiac output (CO), and CPO measured during peak dynamic exercise (i.e. peak CPO) has been shown as a powerful predictor of death for heart failure patients. However, so far there has been no existing device which directly measures CPO, and CPO is acquired from simultaneous measurement of MBP and CO. Further, simultaneous MBP and CO measurement during dynamic exercise is a challenge for current BP and CO methods. Therefore, there is an urgent need to develop new devices which are fully wearable and unobtrusive for monitoring of CPO during dynamic exercise. Since the core problem in most wearable devices is how to estimate the target cardiovascular parameter, e.g. CPO in this study, through physiological signals measured from body surface, this thesis focus on developing a direct measurement technique of CPO in dynamic exercise using multiple physiological signals measured on body surface, specifically, electrocardiogram (ECG) and photoplehtysmogram (PPG). / Finally, based on the theoretical and experimental verifications, linear prediction models were proposed to estimate MBP from PAT and estimate CO from PTRR. The results showed that PAT can estimate MBP with a standard deviation of 7.42 mmHg, indicating PAT model has the potential to achieve the accuracy required by AMMI standard (mean error within +/- 5 mmHg and SD less than 8 mmHg). The results also showed that PTRR can estimate CO with a percent error of 22.57%, showing an accuracy which was considered as clinically acceptable (percent error less than 30%). / Heart failure is the end stage of many cardiovascular diseases, such as hypertension, coronary heart disease, diabetes mellitus, etc. Around 5.8 million people in the United States have heart failure and about 670,000 people are diagnosed with it each year. In 2010, heart failure will cost the United States $30.2 billion, and the cost of healthcare services is a major component of this total. With the resultant burden on health care resources it is imperative that heart failure patients with different risk stages are identified, ideally with objective indicators of cardiac dysfunction, in order that appropriate and effective treatment can be instituted. / In order to verify the theoretical findings, two experiments were carried out. One was incremental supine bicycle exercise conducted on 19 young healthy subjects and the other was incremental to maximum supine bicycle exercise conducted on 65 subjects, including heart failure patients, cardiovascular patients and healthy elderly. PAT showed significantly high and negative correlation with SBP and MBP, but lower correlation with DBP. PTRR showed significantly high and positive correlation with CO. / In this thesis, a model based study is conducted to address the above problem. Firstly, we deduced the mathematical expression of PEP as a function of DBP by introducing the arbitrary heart rate into the exponential mathematical description of a pressure-source model. Secondly, an asymmetric T-tube model was modified by introducing a nonlinear pressure-volume relationship where PTT was expressed as a dependent variant of BP. Thirdly, we proposed the mathematical equation between PAT and BP by coupling the modified ventricular and arterial models. Then, the relationships between PAT with systolic blood pressure (SBP), MBP and DBP were simulated under changing heart contractility, preload, heart rate, peripheral resistance, arterial stiffness and a mimic exercise condition. The simulation results indicated significantly high and negative correlations between PAT and SBP and between PAT and MBP whereas the correlation between DBP and PAT was low. / Next, we developed a novel CO index, namely pulse time reflection ratio (PTRR), expressed in terms of MBP and mean aortic reflection coefficient (Gamma(0)), from the modified asymmetric T-tube model. PTRR was further expressed in terms of PAT and inflection point area (IPA), a surrogate of Gamma(0) from the shape feature of PPG. The simulation results suggested significantly and positive relationship between PTRR and CO and between IPA and Gamma(0) during dynamic exercise. / Recently, a wearable measurable parameter, pulse arrival time or PAT, has been developed for BP measurement. PAT is the time delay from the R peak of ECG to the systolic foot of PPG. PAT consists of two timing components, the pre-ejection period (PEP) of the heart and pulse transit time (PTT). PTT is related to BP by an arterial elastic model and thus can be used to estimate beat-to-beat BP. However, PTT is difficult to be measured through a wearable device, and thus PAT is usually used as a surrogate of PTT for BP estimation, under the assumption of a constant PEP. However, PEP is not a constant but changing with physiological conditions, which may alter the PAT-BP relationship. Thus, it is important to clarify the PAT-BP relationship and address the feasibility of MBP estimation using PAT during dynamic exercise. / To summarize, the original contributions of this thesis are: / Wang, Ling. / Adviser: Y.T. Zhang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Thesis. 1977. B.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 50. / B.S.