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Novel Approaches to the Assessment of Systemic Circulation and Ventricular Performance

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Novel Approaches to the Assessment of Systemic Circulation and Ventricular Performance University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2019-02-27 Novel Approaches to the Assessment of Systemic Circulation and Ventricular Performance Howell, Sarah Howell, S. (2019). Novel Approaches to the Assessment of Systemic Circulation and Ventricular Performance (Unpublished master's thesis). University of Calgary, Calgary, AB. http://hdl.handle.net/1880/109938 master thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Novel Approaches to the Assessment of Systemic Circulation and Ventricular Performance by Sarah Howell A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE GRADUATE PROGRAM IN CARDIOVASCULAR AND RESPIRATORY SCIENCES CALGARY, ALBERTA FEBRUARY, 2019 © Sarah Howell 2019 Abstract The purpose of evaluating the systemic circulation using systemic vascular conductance and head-capacity curve to quantify left ventricle performance is to validate these assessment approaches instead of more commonly used cardiovascular indexes (i.e., systemic vascular resistance and ejection fraction) used for physiologic responses. Systemic vascular conductance is reciprocal of systemic vascular resistance and is defined as the flow to the systemic circulation that determines arterial pressure. Systemic vascular conductance is calculated by dividing cardiac output by arteriovenous pressure difference. Left ventricle performance is assessed using head- capacity curve. It states that left ventricle as a pump, works under a head-capacity curve. The aim of this study is to increase our understanding of systemic circulation and ventricular performance by studying how changing loading conditions using drug interventions (phenylephrine, sodium nitroprusside, and isoproterenol), proximal aortic constriction, and volume loading will affect the systemic vascular conductance and left ventricle performance. The ultimate goal of this study is to combine circulatory and ventricular properties quantitatively and define the relationship between output produced by the heart and input of the circulation. Overall, results are consistent with the hypothesized physiological changes and allow the application of both proposed indices to determine the global cardiovascular performance in a simple manner. These results further enhance our understanding that conductance of each intervention in systemic circulation determines the mean arterial pressure. Systemic vascular conductance changes markedly with changing cardiac index and these changes are mediated by i left ventricle. The potential benefits of these assessment parameters will help provide insights to optimize circulatory performance in patients with cardiovascular disease. ii Acknowledgements First and foremost, I would like to thank Dr. John Tyberg, for his continuous encouragement, advice, support and mentorship. I greatly appreciate him giving me the opportunity to work in his lab and have had a great experience. It has been both a pleasure and privilege for me to obtain my M.Sc. under his guidance. He not only gave me a strong foundation of hemodynamics over the last two years but continued to reinforce my understanding of the subject matter through every stage of my graduate school. Thank you Dr. Tyberg for shaping my critical thinking and helping me mature as a medical scientist. I would also like to thank Dr. Nigel Shrive for his guidance, expertise and approachability. His tough questions and thorough critiques of my written work or data analysis have helped me enormously. Thank you Dr. Shrive for being patient throughout this program and its administrative requirements. My committee members, Dr. Robert Sheldon and Dr. Aaron Phillips require special acknowledgement for their time. Thank you for your guidance and providing invaluable comments regarding important aspects of cardiac physiology. To my examiner, Dr. Paul Fedak thank you for being interested in my project. I appreciate your commitment for reviewing my thesis. In addition, I would also like to thank Dr. Israel Belenkie for his valuable suggestions and advice from a clinical perspective. Although he claims that “the advice is worth as much as you pay for it”, it was still very valued. I also want to express my sincere gratitude to Dr. Henk ter Keurs for his thoughtful critiques and inputs during our discussions. I would like to express my sincere thank you to several additional members of the Tyberg lab, as each one of them were incredibly important for successful completion of this work. Cheryl iii Hall thank you for your much-needed help with experimental procedures. Her surgical expertise is exemplary and constitutes a crucial part of this study. Her fun-loving nature made my graduate learning experience enjoyable and memorable. John Nystrom’s unrelenting patience with all the technical issues and providing the best technical support possible was immensely helpful for entire data analysis. Dr. Carol Gibbons Kroeker thank you for taking the time to teach me Sigma Plot and your willingness to help in any way possible. A sincere gratitude goes to Dr. Lindsay Burrowes for being a constant source of support and mentorship since my arrival to the lab. Thank you for teaching me how to perform and troubleshoot data analysis using MATLAB and other software. I am extremely thankful for your kindness and patience for answering all my questions ranging from mathematical concepts to cardiovascular physiology. This study would not have been possible without your significant contributions. I must also thank Anukul Ghimire for helping me get started in the lab and provide answers to my countless questions about the basics of reservoir-wave approach, MATLAB and physiology concepts. Thank you also to Maryell Lopez for making lab an enjoyable place to work. I am indebted to my family for their unwavering support and unconditional love during graduate school and throughout life. Despite my worries, they never doubted my ability to complete this manuscript. I am incredibly blessed to have such parents, aunt, parents-in-law, siblings and brothers-in-law. Mama, papa and phopho, I owe you an enormous unrepayable debt of gratitude for all your sacrifices and to show my gratitude I dedicate this thesis to you. Last but certainly not least, special thanks go to my husband, Jadeon who has been my constant support in many significant ways. I simply cannot thank him enough for his patience, love, and iv encouragement. Thank you for always putting a smile on my face and making my world shine brighter every day. v Table of Contents Abstract ............................................................................................................................................ i Acknowledgements ........................................................................................................................ iii List of Figures .............................................................................................................................. viii List of Tables ................................................................................................................................ xii List of Symbols, Abbreviations and Nomenclature ..................................................................... xiii Chapter One: Introduction .............................................................................................................. 1 Chapter Two: Background .............................................................................................................. 3 2.1 Cardiovascular System .......................................................................................................... 3 2.1.1 Cardiac Cycle and Pressure Volume Loop ........................................................................ 4 2.1.2 Pressure Volume Relationship ........................................................................................... 9 2.1.3 Cardiovascular Models ..................................................................................................... 14 2.1.3.1 Literature Review of Evaluation of the Systemic Circulation ................................... 15 2.1.3.2 Systemic Vascular Conductance ............................................................................... 20 2.1.3.3 Literature Review of Ventricular Performance ......................................................... 25 2.1.3.4 Head-Capacity Approach .......................................................................................... 30 2.2 Goals.................................................................................................................................... 36 2.3 Rationale.............................................................................................................................. 36 Chapter Three: Methods ............................................................................................................... 38 3.1 Animal Preparation ............................................................................................................. 38 3.2
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