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The Effects of Nicotine and Cigarette Smoking on Cardiac Electrophysiology

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The Effects of Nicotine and Cigarette Smoking on Cardiac Electrophysiology University of Louisville ThinkIR: The University of Louisville's Institutional Repository Electronic Theses and Dissertations 12-2019 The effects of nicotine and cigarette smoking on cardiac electrophysiology. Affan B. Irfan University of Louisville Follow this and additional works at: https://ir.library.louisville.edu/etd Part of the Cardiology Commons, Cardiovascular Diseases Commons, Medical Physiology Commons, and the Preventive Medicine Commons Recommended Citation Irfan, Affan B., "The effects of nicotine and cigarette smoking on cardiac electrophysiology." (2019). Electronic Theses and Dissertations. Paper 3319. https://doi.org/10.18297/etd/3319 This Doctoral Dissertation is brought to you for free and open access by ThinkIR: The University of Louisville's Institutional Repository. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of ThinkIR: The University of Louisville's Institutional Repository. This title appears here courtesy of the author, who has retained all other copyrights. For more information, please contact [email protected]. THE EFFECTS OF NICOTINE AND CIGARETTE SMOKING ON CARDIAC ELECTROPHYSIOLOGY By Affan B. Irfan M,B.B,S Aga Khan University, 2008 A Dissertation Submitted to the Faculty of the School of Medicine of the University of Louisville In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Physiology and Biophysics Department of Physiology University of Louisville Louisville, Kentucky December 2019 THE EFFECTS OF NICOTINE AND CIGARETTE SMOKING ON CARDIAC ELECTROPHYSIOLOGY By Affan B. Irfan M,B.B,S Aga Khan University, 2008 A Dissertation Approved on November 27, 2019 by the following Dissertation Committee: Dr Aruni Bhatnagar (Dissertation Director) Dr Alex Carll (Co-Director) Dr. Andrew P. DeFilippis Dr. Irving G. Joshua Dr. Dale A. Schuschke ii DEDICATION This dissertation is dedicated to my parents, Irfan Uddin and Farzana Irfan, (without whom I would not have been here), my brother, Furqan Irfan, and sister Bismah Irfan, (without whom I would not have been the middle child), and my wife, Sommaya Naveed, and our daughter, Aiza Affan (without whom this dissertation would have been completed a year ago). iii ACKNOWLEDGEMENTS Firstly, I am indebted to Dr. Aruni Bhatnagar, for giving me the opportunity to complete my Ph.D dissertation under his supervision, and also to Dr. Glenn Hirsch and the University of Louisville Cardiovascular Fellowship Program, for allowing me to participate in the Ph.D graduate studies during my fellowship training. I particularly would like to thank my mentors, Dr. Bhatnagar and Dr. Alex P. Carll, for their tireless guidance and “tough love” that pushed me out of my comfort zone (of just being a physician), and onto the path of a successful (and humble) scientist. I would like to thank the rest of my dissertation committee members (Dr. Andrew P. DeFilippis, Dr. Irving G. Joshua, and Dr. Dale A. Schuschke) for their support and invaluable advice. I am also especially grateful to Dr. Andrew P. DeFilippis for his expertise in clinical research studies that contributed greatly to this research. Moreover, I am thankful to Dr. Elsayed Soliman for his advice, collaboration, and contribution to projects related to this dissertation. This work would not have been possible without the administrative and financial support of Marshall University’s Departments of Cardiology and Clinical Translational Services. I am especially grateful to research coordinators, Melissa Marcum and Scott Wiley, for their perseverance and unwavering commitment to this research study. I am greatly indebted to, and honored by, the encouragement and guidance from Dr. Christian Mueller, who introduced me to cardiovascular research and helped take the first steps of my scientific pursuits. Lastly, I thank my dear family, especially my mother, father, brother, sister, and wife for their enduring love, support, and sacrifice. iv ABSTRACT THE EFFECTS OF NICOTINE AND CIGARETTE SMOKING ON CARDIAC ELECTROPHYSIOLOGY Affan B. Irfan November 27, 2019 Cigarette smoking is a leading cause of preventable disease and premature death worldwide. The adverse effects of cigarette smoking, including proarrhythmia, are related to the mixture of chemicals, including nicotine (which sustains tobacco addiction). However, it remains unclear which individual tobacco smoke constituents and biological pathways mediate this increased risk. The purpose of this research was to explore the chronic effects of cigarette smoking, as well as compare the acute effects of nicotine and cigarette smoking, and the possible role of β-adrenoreceptors, on human cardiac electrophysiology. Chapter 1 is a comprehensive literature review of (a) the ex vivo and in vivo effects of nicotine and non-nicotine constituents of cigarette smoking on cardiac ion channels, (b) the direct and indirect effects of the autonomic nervous system on cardiac electrophysiology, and (c) studies of acute and chronic effects of cigarette smoking in humans. Chapter 2 consists of two studies in which we used cotinine levels to investigate the differences in baseline cardiac electrocardiogram between chronic smokers and non- smokers, and to define smoking status and its burden. We also explored the relationship between urinary catecholamines, cotinine, and electrocardiographic changes. Chapter 3 features the 2 x 2 factorial experimental study designed to compare v the acute effects of cigarette smoking and nicotine, with and without a β-blocker (propranolol). We found that chronic cigarette smoking was associated with a shortened PR segment at baseline, and that dopamine possibly mediates this effect. There was also (corrected) QT interval shortening with increased cotinine levels. This experimental study revealed that the non-nicotine constituents in cigarette smoking were mainly responsible for PR segment shortening, through β-adrenoreceptors. Other evidence revealed that, although nicotine in cigarette smoke is primarily responsible for sympathetic activation and (corrected) QT interval shortening, it is the non-nicotine constituents that depress the ST segment. Collectively, acute and chronic exposure studies indicate that smoking may promote cardiac arrhythmia, primarily via β-adrenoreceptors, causing acceleration of dromotropy and ischemia (non-nicotine mediated), and ventricular repolarization (nicotine-mediated). This research elucidated a major physiological mechanism driving the effect of cigarette smoking and nicotine on cardiac electrophysiology. Consequently, these findings will inform U.S. Food and Drug Administration of tobacco and nicotine- containing products’ impact on the human cardiac electrical system, and potentially help regulate alternative forms of nicotine delivery and protect public health. vi TABLE OF CONTENTS PAGE ACKNOWLEDGEMENTS ............................................................................................ iv ABSTRACT ..................................................................................................................... v LIST OF TABLES .......................................................................................................... ix LIST OF FIGURES .......................................................................................................... X CHAPTER I. INTRODUCTION ..................................................................................... 1 Background and context ............................................................................................... 1 Clinical significance of cigarette smoking, nicotine, and cardiac electrophysiology ...................................................................................................... 1 Effects of cardiac autonomic system and cigarette smoke on cardiac action potential .......................................................................................................... 7 Literature review of effects of autonomic nervous system and smoking on electrocardiogram .................................................................................................... 32 Hypothesis ................................................................................................................... 44 Ethical considerations ............................................................................................. 45 CHAPTER II CHRONIC EFFECTS OF CIGARETTE SMOKING ON ELECTROCARDIOGRAM ........................................................................................... 46 Cigarette smoking, ECG and interaction with Atrioventricular nodal blockers ............................................................................................................. 46 Participants from NHANES database ..................................................................... 45 Results ..................................................................................................................... 52 Discussion ............................................................................................................... 61 Conclusions ............................................................................................................. 64 Effects of cigarette smoking on electrocardiogram mediated via catecholamines ...................................................................................................... 65 Participants from Louisville Healthy Heart Study .................................................. 65 Results ....................................................................................................................
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