The role of cardiopulmonary exercise testing for identifying possible silent myocardial ischaemia in people with coronary heart disease

This thesis investigates the utility of cardiopulmonary exercise testing (CPET) in assessing and managing patients with coronary artery disease (CAD), particularly focusing on the significance of oxygen pulse (O2Pulse) inflections as a marker for myocardial ischemia. The research encompasses a comprehensive analysis of O2Pulse morphology, inflection point identification, and the impact of exercise-based cardiac rehabilitation (exCR) programs, specifically high-intensity interval training (HIIT) and moderate-intensity steady-state (MISS) training, on patients with CHD.Chapter 3 examines the reliability of CPET in detecting suspected myocardial ischemia through O2Pulse and ΔV̇O2/ΔWR inflections in chronic total occlusion (CTO) patients. This study was considerable hampered by poor recruitment and the outbreak of COVID-19. Subsequently only four patients were enrolled, three of whom exhibited no inflections in O2Pulse. In the one patient who did have O2Pulse inflections they occurred at similar work rates (10W) and heart rates (5bpm). Chapter 5 extends the inquiry into the short-term reliability and agreement of O2Pulse curve parameters in a healthy cohort demonstrating that the mean percent minimal detectable change for filtered O2Pulse was 13.5 ± 3.2. Building on these findings, Chapter 6 evaluates the inter- and intra-rater reliability in identifying O2Pulse inflections, comparing subjective assessments with an objective algorithmic method. Almost perfect agreement between the algorithm and human raters was demonstrated, with a Fleiss’ Kappa statistic of 0.89. Chapter 7, a subset analysis from the HIIT or MISS UK trial, delves into the rate of O2Pulse inflections in outpatient cardiac rehabilitation (16%) and how different exercise interventions affect O2Pulse inflections in CAD patients.The results highlight a considerable potential for CPET, particularly O2Pulse inflections, in the diagnosis, treatment, and management of CAD. The research underscores the potential reliability of O2Pulse as a diagnostic tool, the effectiveness of exCR in improving cardiopulmonary fitness, and the relevance of O2Pulse inflections as a surrogate marker for myocardial ischemia. The findings suggest that both HIIT and MISS can positively influence O2Pulse inflections, offering a non-invasive means to monitor and potentially improve the health outcomes of CAD patients.This thesis contributes to the understanding of CPET in clinical settings, advocating for its broader application in cardiac rehabilitation. It identifies areas for further research, including the exploration of different exercise modalities, to optimize exCR programs and enhance patient care

Computational methods for physiological data

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2009.Author is also affiliated with the MIT Dept. of Electrical Engineering and Computer Science. Cataloged from PDF version of thesis.Includes bibliographical references (p. 177-188).Large volumes of continuous waveform data are now collected in hospitals. These datasets provide an opportunity to advance medical care, by capturing rare or subtle phenomena associated with specific medical conditions, and by providing fresh insights into disease dynamics over long time scales. We describe how progress in medicine can be accelerated through the use of sophisticated computational methods for the structured analysis of large multi-patient, multi-signal datasets. We propose two new approaches, morphologic variability (MV) and physiological symbolic analysis, for the analysis of continuous long-term signals. MV studies subtle micro-level variations in the shape of physiological signals over long periods. These variations, which are often widely considered to be noise, can contain important information about the state of the underlying system. Symbolic analysis studies the macro-level information in signals by abstracting them into symbolic sequences. Converting continuous waveforms into symbolic sequences facilitates the development of efficient algorithms to discover high risk patterns and patients who are outliers in a population. We apply our methods to the clinical challenge of identifying patients at high risk of cardiovascular mortality (almost 30% of all deaths worldwide each year). When evaluated on ECG data from over 4,500 patients, high MV was strongly associated with both cardiovascular death and sudden cardiac death. MV was a better predictor of these events than other ECG-based metrics. Furthermore, these results were independent of information in echocardiography, clinical characteristics, and biomarkers.(cont.) Our symbolic analysis techniques also identified groups of patients exhibiting a varying risk of adverse outcomes. One group, with a particular set of symbolic characteristics, showed a 23 fold increased risk of death in the months following a mild heart attack, while another exhibited a 5 fold increased risk of future heart attacks.by Zeeshan Hassan Syed.Ph.D

Data Mining and Machine Learning to Predict Acute Coronary Syndrome Mortality

This thesis has investigated and demonstrated the potential for developing prediction models using Machine Learning(ML) algorithms on registry datasets. Many current Acute Coronary Syndrome (ACS) prediction models, were developed using traditional statistical methods. In an era of big-data evolution, ML offers a spectrum of algorithms that aid in generating prediction models for ACS. This study has explored 29 algorithms with which to build ACS prediction models for Asian (Malaysia) and Western (Leeds, UK) registries, covering patients with all types of ACS and those with the new standard ACS treatments. The internal and external validation of the models present satisfactory calibration measures, indicating the ability of ML algorithms to produce competitive models in comparison to traditional statistical methods. To achieve simpler, yet competitive predictive performance, comprehensive ML feature selection methods have been evaluated, and Correlation-Based-Feature-Selection(CFS) emerged as the best method. This thesis also has evaluated the potential of predictors of existing ACS models to be adapted to other registries‘ data. Despite different regions and different population characteristics, most of the existing predictors remains constant with the outcome. Thus, the findings suggest that, with some adjustments customized to the registry, the existing predictors can be adopted to develop a simple model and expedite the model development process. Furthermore, the strength of the predictors of each clinical categories has also been evaluated. The results suggest that, to construct a satisfactory ACS model, combination of predictors from various clinical events is essential. At the very least, to achieve a satisfactory model, combination of demographic, medical history, and clinical presentation information categories is required. However, predictors from medication history category has found to be worthless in terms of contributing to a better prediction model. Next, this study has investigated classifier degradation in ML model development. The findings suggest that the overlapping instances in minority class of imbalanced dataset and missing values are the main problems of classifier degradation. New methods i.e. the overlapped-undersampling method to handle imbalanced dataset and the mean-clustering-imputation method to handle missing values have been introduced. The overlapped-undersampling failed to boost the model performance of the datasets. Nevertheless, the results suggest that more training samples on imbalanced datasets are sufficient to produce satisfactory models. The mean-clustering-imputation method produced better models compare to the simple imputation method and imputation method embedded in an algorithm. However, removing instances with missing data resulted in superior models

Front Lines of Thoracic Surgery

Front Lines of Thoracic Surgery collects up-to-date contributions on some of the most debated topics in today's clinical practice of cardiac, aortic, and general thoracic surgery,and anesthesia as viewed by authors personally involved in their evolution. The strong and genuine enthusiasm of the authors was clearly perceptible in all their contributions and I'm sure that will further stimulate the reader to understand their messages. Moreover, the strict adhesion of the authors' original observations and findings to the evidence base proves that facts are the best guarantee of scientific value. This is not a standard textbook where the whole discipline is organically presented, but authors' contributions are simply listed in their pertaining subclasses of Thoracic Surgery. I'm sure that this original and very promising editorial format which has and free availability at its core further increases this book's value and it will be of interest to healthcare professionals and scientists dedicated to this field

Patients' Health Related Quality of Life After Coronary Revascularization: A Longitudinal Mixed Method Study

Aims: Coronary Revascularization (CR) has increased patients’ survival rate globally. However, the lack of a consensus definition of Health Related Quality of Life (HRQoL) and the different methodological and conceptual approaches adopted by researchers in the cardio-revascularization field create an incomplete picture of the influence of CR on individuals’ HRQoL. By using mixed methodology, the current research aimed to explore Greek CHD patients’ perspectives of their HRQoL after CR (Coronary Artery Bypass Grafting (CABG) or Percutaneous Coronary Interventions (PCI)), as well as detect and explain individual disparities. Method: Two studies were conducted with a total sample of 487 individuals: (1) The translation and validation of the Coronary Revascularization Outcome Questionnaire (CROQ) into Greek and (2) The longitudinal mixed methods study, the main study of the thesis, following a sequential explanatory design with two research components: a) the longitudinal quantitative component aimed to detect changes in patients’ HRQoL (both overall and its subdomains) following CR over a 12-month period based on individuals’ subjective evaluation as captured by the CROQ, detect the influence of CR type on the outcome and to explore potential predictors (individuals’ demographic, clinical and behavioural features). Data were analysed using multilevel modelling; b) the qualitative component aimed to capture individuals’ lived experience, their view and understanding of themselves and their life approximately 12 months after treatment using Interpretive Phenomenological Analysis (IPA). Results/findings: Based on participants’ subjective evaluations as captured by the validated Greek version of the CROQ, one year after CR Greek Coronary Heart Disease (CHD) patients experience an increase in their HRQoL level compared to prior to CR. The pattern of change though is not constant; initially HRQoL increases with time, and then decreases again, however, remaining much greater compared to prior to CR one year after CR. Regarding the influence of the CR type of treatment on patients’ HRQoL level, a year after CR mixed findings are revealed. In the symptoms and physical functioning subdomain, patients treated with CABG demonstrate a greater increase compared to patients treated with PCI. In the psychosocial functioning subdomain no difference is found. In the cognitive functioning subdomain, patients treated with CABG demonstrate a decline compared to their cognitive functioning prior to the CR. Various demographic, clinical and behavioural features are demonstrated to be predictors of the outcome though not consistent for all subdomains. The main predictors associated with larger positive changes following CR seem to be sex, BMI and smoking; females with low BMI that do not smoke tend to demonstrate a greater increase in HRQoL after CR. According to individuals’ lived experience, participants, reflecting on their experience one year after treatment, perceive CR as a simple process and their negative experience is mostly related to medical care. Many participants with no symptoms or adverse effects tend to misperceive CHD, viewing their health condition as an acute disease treated with CR. Trying to understand disease causality they tend to adopt medical discourse especially in relation to stress as a factor that can be controlled by themselves and reflect on their own responsibility as a causal factor. Feeling grateful for being alive, sensing a different body, a “revitalized body” as many participants suggest, as well as a fear of re-occurrence or disease progression motivate individuals to work on aspects of the self related to the CHD development in an effort to regain control over their life which has been reduced after the CHD diagnosis. In effect a dramatic change in how the self and life are viewed is reported, highlighting a positive growth; a greater appreciation of life, a personal growth and effort to build more meaningful relationships. Challenges that participants face in modification of their lifestyle are attributed to both external and internal factors. Concerning smoking participants’ accounts point to a lack of knowledge regarding the relationship between smoking and CHD, a lack of support (by experts or family members) and conscious denial as a way to cope with every day anxiety and stress, but also a pleasure in everyday life. The findings provide a complementary insight into perceptions of individuals with CHD about their quality of life one year after CR, suggesting that other factors beyond CR may influence their perspectives. Conclusions/implications: This study highlights the benefits of using a mixed methods longitudinal design in exploring HRQoL. Both the quantitative and qualitative findings support the notion that HRQoL is a multidimensional, continuously changing concept, providing support for the Wold Health Organization’s definition. Also, the findings suggest that CR has a positive influence on individuals’ HRQoL. The effect of the CR type needs further investigation as mixed findings are observed in the present thesis. Moreover, it seems difficult to investigate the pure effect of CR on individuals’ HRQoL without taking into consideration individuals’ adjustment processes and positive growth triggered by the CR. The self regulation model (SRM) might be considered a useful theoretical framework for developing theory-based interventions aiming to alter patients’ false beliefs since individuals’ making-meaning process seems to be aligned with it. Finally, the complementary insights concerning smoking may help health care providers to develop smoking cessation interventions tailored to cardiac patients

Patients' Health Related Quality of Life After Coronary Revascularization: A Longitudinal Mixed Method Study

Aims: Coronary Revascularization (CR) has increased patients’ survival rate globally. However, the lack of a consensus definition of Health Related Quality of Life (HRQoL) and the different methodological and conceptual approaches adopted by researchers in the cardio-revascularization field create an incomplete picture of the influence of CR on individuals’ HRQoL. By using mixed methodology, the current research aimed to explore Greek CHD patients’ perspectives of their HRQoL after CR (Coronary Artery Bypass Grafting (CABG) or Percutaneous Coronary Interventions (PCI)), as well as detect and explain individual disparities. Method: Two studies were conducted with a total sample of 487 individuals: (1) The translation and validation of the Coronary Revascularization Outcome Questionnaire (CROQ) into Greek and (2) The longitudinal mixed methods study, the main study of the thesis, following a sequential explanatory design with two research components: a) the longitudinal quantitative component aimed to detect changes in patients’ HRQoL (both overall and its subdomains) following CR over a 12-month period based on individuals’ subjective evaluation as captured by the CROQ, detect the influence of CR type on the outcome and to explore potential predictors (individuals’ demographic, clinical and behavioural features). Data were analysed using multilevel modelling; b) the qualitative component aimed to capture individuals’ lived experience, their view and understanding of themselves and their life approximately 12 months after treatment using Interpretive Phenomenological Analysis (IPA). Results/findings: Based on participants’ subjective evaluations as captured by the validated Greek version of the CROQ, one year after CR Greek Coronary Heart Disease (CHD) patients experience an increase in their HRQoL level compared to prior to CR. The pattern of change though is not constant; initially HRQoL increases with time, and then decreases again, however, remaining much greater compared to prior to CR one year after CR. Regarding the influence of the CR type of treatment on patients’ HRQoL level, a year after CR mixed findings are revealed. In the symptoms and physical functioning subdomain, patients treated with CABG demonstrate a greater increase compared to patients treated with PCI. In the psychosocial functioning subdomain no difference is found. In the cognitive functioning subdomain, patients treated with CABG demonstrate a decline compared to their cognitive functioning prior to the CR. Various demographic, clinical and behavioural features are demonstrated to be predictors of the outcome though not consistent for all subdomains. The main predictors associated with larger positive changes following CR seem to be sex, BMI and smoking; females with low BMI that do not smoke tend to demonstrate a greater increase in HRQoL after CR. According to individuals’ lived experience, participants, reflecting on their experience one year after treatment, perceive CR as a simple process and their negative experience is mostly related to medical care. Many participants with no symptoms or adverse effects tend to misperceive CHD, viewing their health condition as an acute disease treated with CR. Trying to understand disease causality they tend to adopt medical discourse especially in relation to stress as a factor that can be controlled by themselves and reflect on their own responsibility as a causal factor. Feeling grateful for being alive, sensing a different body, a “revitalized body” as many participants suggest, as well as a fear of re-occurrence or disease progression motivate individuals to work on aspects of the self related to the CHD development in an effort to regain control over their life which has been reduced after the CHD diagnosis. In effect a dramatic change in how the self and life are viewed is reported, highlighting a positive growth; a greater appreciation of life, a personal growth and effort to build more meaningful relationships. Challenges that participants face in modification of their lifestyle are attributed to both external and internal factors. Concerning smoking participants’ accounts point to a lack of knowledge regarding the relationship between smoking and CHD, a lack of support (by experts or family members) and conscious denial as a way to cope with every day anxiety and stress, but also a pleasure in everyday life. The findings provide a complementary insight into perceptions of individuals with CHD about their quality of life one year after CR, suggesting that other factors beyond CR may influence their perspectives. Conclusions/implications: This study highlights the benefits of using a mixed methods longitudinal design in exploring HRQoL. Both the quantitative and qualitative findings support the notion that HRQoL is a multidimensional, continuously changing concept, providing support for the Wold Health Organization’s definition. Also, the findings suggest that CR has a positive influence on individuals’ HRQoL. The effect of the CR type needs further investigation as mixed findings are observed in the present thesis. Moreover, it seems difficult to investigate the pure effect of CR on individuals’ HRQoL without taking into consideration individuals’ adjustment processes and positive growth triggered by the CR. The self regulation model (SRM) might be considered a useful theoretical framework for developing theory-based interventions aiming to alter patients’ false beliefs since individuals’ making-meaning process seems to be aligned with it. Finally, the complementary insights concerning smoking may help health care providers to develop smoking cessation interventions tailored to cardiac patients