Coronary Circulation

Research centering on blood flow in the heart continues to hold an important position, especially since a better understanding of the subject may help reduce the incidence of coronary arterial disease and heart attacks. This book summarizes recent advances in the field; it is the product of fruitful cooperation among international scientists who met in Japan in May, 1990 to discuss the regulation of coronary blood flow.

Few diagnostic methods in Cardiology have heralded such revolutionary developments as the introduction of coronary arteriography. When, in the early 1960's, Dr. F. Mason Sones demonstrated that visualization of the coronary anatomy in living humans was not only feasible but sufficiently safe and reliable to be used as a clinical tool in the evaluation of patients with known or suspected ischemic heart disease, the thus far somewhat neglected area of coronary circulation became the focus of interest. Naturally, for a considerable period of time a great deal of emphasis was placed upon coronary anatomy. Simple relations between narrowing lesions, impediment to flow, and prognosis were assumed to exist. Spectacular results of surgical coronary revascularization seemed to confirm this concept. Gradually it has become evident that the pathophysiology of coronary artery disease is considerably more complex. Diagnostic methods were introduced to assess and quantify exercise-induced myocardial ischemia. At first, these tests were used mainly to achieve a more discriminative selection of candidates for coronary arteriography and the coronary arteriogram remained the gold standard. Currently, these techniques have evolved to the point where they provide valuable functional and metabolic information. They have become powerful independent tools in clinical investigations and evaluation of individual patients.

The coronary circulation is unique in that it is responsible for maintaining adequate oxygen and substrate delivery to the organ that generates the pressure needed to drive blood throughout the entire circulatory system. In the simplest terms, coronary blood flow is directly proportional to the arterial pressure gradient across the coronary vasculature and inversely proportional to coronary vascular resistance. However, myocardial perfusion is collectively regulated by a complex variety of mechanisms which include: (1) extravascular compressive forces; (2) diastolic time fraction; (3) coronary perfusion pressure; (4) myocardial metabolism (local metabolic factors); (5) endothelial-derived substances; (6) neuro-humoral influences; and (7) arterial oxygen tension and content. This book considers each of these determinants with particular emphasis on the functional interaction between the physical and biological determinants of myocardial perfusion. Pathophysiologic aspects of coronary atherosclerosis and cardiovascular disease states are also considered. Table of Contents: Abbreviations / Acknowledgments / Introduction / Basic Coronary Anatomy / Myocardial-Coronary Interaction / Arterial Pressure and Autoregulation / Local Metabolic Control / Endothelial-Dependent Control / Neural Activation and Circulating Hormones / Coronary Stenosis, Myocardial Ischemia, and Effects of Disease / Summary / Reference List / Author Biography

This comprehensive text examines both global and local coronary blood flow based on morphometry and mechanical properties of the coronary vasculature. Using a biomechanical approach, this book addresses coronary circulation in a quantitative manner based on models rooted in experimental data that account for the various physical determinants of coronary blood flow including myocardial-vessel interactions and various mechanisms of autoregulation. This is the first text dedicated to a distributive analysis (as opposed to lumped) and provides digital files for detailed anatomical data (e.g., diameters, lengths, node-to-node connections) of the coronary vessels. This book also provides appendices with specific mathematical formulations for the biomechanical analyses and models in the text. Written by Dr. Ghassan S. Kassab, a leader in the field of coronary biomechanics, Coronary Circulation: Anatomy, Mechanical Properties, and Biomechanics is a synthesis of seminal topics in the field and is intended for clinicians, bioengineers, and researchers as a compendium on the topic. The detailed anatomical and mechanical data provided are intended to be used as a platform to address new questions in this exciting and clinically very important research area.

Considerable advances have been made in cardiology during the last few decades. In particular, there has been great progress in the field of coronary angiography both when combined with, and without, computed tomography (CT) and magnetic reso nance (MR) imaging. These techniques of modern imaging allow the cardiologist and coronary surgeon to study every cardiac structure in detail, both two- and three-di mensionally and from either side, to analyze the movements of the heart and valves, and to observe myocardial circulation and even myocardial metabolic processes. However, coronary heart disease, a multifactorial illness of the coronary vessels, still remains the most common cause of death in developed countries. In addition to the large group of patients suffering from coronary heart disease, there is a smaller group of children and adults who are in need of open heart surgery and,most frequently,valve surgery.Avery small number of individuals suffering from Wolff-Parkinson-White syndrome still await competent surgical intervention. These three groups of patients have in common that, for them, meticulous preop erative diagnostics and preparation for surgery are urgently required. Any open heart surgeon who carri es out procedures in the coronary or interventricular grooves or on the atrial walls of the heart must take the normal and anomalous origins,courses, and terminations of cardiac vessels into consideration. Therefore, with the availability of precise anatomical and physiological data,operation time will be shortened, operative risks will diminish, and the safety of the operation for the patient will be greater.

The fields of biological and medical physics and biomedical engineering are broad, multidisciplinary and dyanmic. They lie at the crossroads of frontier - search in physics, biology, chemistry, and medicine. The Biological & Me- cal Physics/Biomedical Engineering Series is intended to be comprehensive, covering a broad range of topics important to the study of the physical, che- cal and biological sciences. Its goal is to provide scientists and engineers with textbooks, monographs, and reference works to address the growing need for information. Books in the series emphasize established and emergent areas of science - cluding molecular, membrane, and mathematical biophysics; photosynthetic - ergy harvesting and conversion; information processing; physical principles of genetics; sensory communications; automata networks, neural networks, and cellular automata. Equally important will be coverage of applied aspects of b- logical and medical physics and biomedical engineering such as molecular el- tronic components and devices, biosensors, medicine, imaging, physical prin- ples of renewable energy production, advanced prostheses, and environmental control and engineering. Elias Greenbaum Oak Ridge, TN M. Zamir Department of Applied Mathematics University of Western Ontario London, Ontario, N6A 5B7 CANADA zamir@uwo.ca Library of Congress Cataloging-in-Publication Data Zamir, M. (Mair) The physics of coronary blood flow / M. Zamir. p. cm. — (Biological and medical physics, biomedical engineering) Includes bibliographical references and index. 1. Coronary circulation. 2. Hemodynamics. 3. Blood flow. I. Title. II. Series. QP108.Z36 2005 612.1?7—dc22 2005042502 ISBN-10: 0-387-25297-5 e-ISBN: 0-387-26019-6 Printed on acid-free paper.

by JULIEN IE HOFFMAN One of the earliest coronary physiologists was Scaramucci who, in 1695, postu lated that during systole the contracting myocardium inhibited coronary blood flow. Since then, the many contributions that have been made to our knowledge of the coronary circulation can be arbitrarily divided into three phases based on advances in technical methods. The early phase of research into the coronary circulation, done with great difficulty with crude methods, may be regarded as ending in the 1940s, and it included major discoveries made by such well known investigators as Georg von Anrep, Ernest Starling, Carl Wiggers, and Louis Katz, who formulated much of our basic understanding of the field. After 1940, the field of coronary physiology entered a new phase when instruments for high fidelity registration of coronary flow and pressure became available. This era was domi nated by Donald Gregg who combined careful attention to the function of these instruments (some of which he helped to develop) with an extraordinary ability to discern mechanisms from apparently minor changes in coronary flow and pressure patterns. His book 'The Coronary Circulation in Health and Disease' set a new standard in the field. After 1960, techniques for measuring regional myocardial blood flow became available, and enabled a large group of eminent investigators to make major advances in understanding the physiology and pathophysiology of myocardial blood flow.

Coronary heart disease is one of the major health problems in indus trialized nations because of its high incidence and severity. Recent innovations in medical and surgical treatment of coronary heart dis ease have increased the importance of accurate diagnostic methods for determining the severity of coronary disease, identifying potential treatment alternatives, and evaluating the results of treatment. Great advances have also been made in basic research on coronary circula tion and its interaction with myocardial contraction and relaxation and neural and humoral control. With respect to these developments, the papers included in the present monograph deal with important topics concerned with the basic mechanism of coronary circulation as well as ones of clinical relevance. It is directed toward physicians (cardiologists, cardiac surgeons, cardiac radiologists, anestheologists, and others) and basic scientists (e.g., physiologists, bioengineers). We would like to em phasize the importance of a multidisciplinary approach in which basic scientists and clinicians work closely together. This volume consists of nine chapters. Chapter 1 contains macro scopic and microscopic descriptions of coronary vascular anatomy, which is closely related to the functions of coronary circulation. In Chap. 2 two methods in current use to evaluate phasic coronary blood velocity waveforms are presented, i.e., the laser Doppler and ultrasound Doppler methods. Chapter 3 describes the mechanical properties of coronary circulation, a knowledge of which is indispens able for an understanding of coronary arterial and venous blood flow velocity waveforms in relation to cardiac contraction and relaxation.