Coronary Blood Flow

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.

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.

The ultrasound velocity tomography allows measurement of cardiac geometries for various phases in the cardiac cycle. The present tomograph makes reconstruc tions at intervals of 20 ms. Because of a lack of clear (intramural) landmarks (except the roots of the papillairy muscle), it is difficult to pinpoint spatial trajectories of particular points in the heart. Therefore, a second method was developed of injecting radiopaque markers in the heart and following their motion patterns during the cardiac cycle with help of a biplane X-ray equipment. The data obtained with both methods can be implemented in our finite element model of the heart to compute intramural stresses and strains. The results obtained sofar with the extended Darcy equation to account for the interaction of blood rheology and tissue mechanics look promising. Further testing with more sophisticated subjects than mentioned in Figure 9 is required before it will be implemented in our finite element model of the heart. We conclude that analysis of regional cardiac function, including regional myocardial blood flow, requires still a major research effort but the results obtained sofar justify, to our opinion, a continuation in this direction. Acknowledgement The authors acknowledge Dr. C. Borst and coworkers for doing the animal experiments and prof. Van Campen and dr. Grootenboer for their participation is some aspects of this work.

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

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.

Covers all of the equations that candidates need to understand and be able to apply when sitting postgraduate anaesthetic examinations.

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.