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 [email protected] 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.
MOTOOMI NAKAMURA As we approach the 21st century, ischemic heart disease is the major cause of death in most of the developed nations of the world. Since the 1970s, much effort and expense have led to designs of coronary thrombolytic therapy, percutaneous coronary angioplasty (PTCA), coronary artery bypass grafting, heart transplantation, automatic defibrillators, as well as to the formation of beta blockers and com pounds which block the calcium channel. Socio-educational programs directed at exercise, diet, instruction in the risk factors of smoking, hyperlipidemia and hypertension have contributed to the decrease in the rate of morbidity and mortality of patients with ischemic heart disease. However, the first clinical event of ischemic heart disease, the so-called "heart attack" and sudden cardiac death continues to present problems, as the mechanisms involved in these events are poorly understood. It has long been thought that ischemic heart disease is the sequence of an organic fixed atherosclerotic obstruction of the epicardial coronary arteries and the role of coronary vasomotion has been given much less attention. Recent clinical and laboratory animal studies revealed that increased tonus and spasm of the large epicardial coronary arteries are the cause of various stages of ischemic heart disease. The role of coronary vasospasm in the development of un stable angina, sudden cardiac death and acute myocardial infarction remains open to debate. Pharmacophysiological studies showed that the epicardial large coronary artery contributes only 5% to regulation of normal coronary flow.
Cardiologists must answer three important questions when evaluating and treating patients with a coronary artery stenosis. As a physiologist: "What is the effect of this stenosis on coronary blood flow and myocardial function?"; as a clinician: " Is this lesion responsible for the patient's symptoms?"; and finally as an interventionalist: "Will revascularization of this artery improve the patient?" Fundamentally, the answer to these questions can be given to a large extent by measuring coronary pressure. That is the rationale of writing this book. 1. 1 Historical overview. Andreas Gruentzig and most interventional cardiologists in the early days of PTCA, had the intuitive feeling that pressure measurements could help to establish the severity of a coronary stenosis and to monitor the progress and result of a coronary intervention. At that time, measuring coronary pressure by the balloon catheter was part of a standard procedure. A residual transstenotic gradient of less than 15 mmHg was generally considered as a good result. Later, however, it turned out that measuring these (resting) gradients with balloon catheters was inaccurate an only had a limited prognostic value. Moreover, because there was no consistent theory to correlate pressure measurements to blood flow, the interest in measuring coronary pressures faded and disappeared almost completely with the introduction of new balloon catheters not intended for pressure measurement.
Interventional cardiology has transitioned from angiographic subjective analysis of stenosis severity into assessment of plaque characteristics and objective assessment of stenosis severity. The evolution of novel interventional imaging modalities is progressively altering our understanding of coronary artery disease diagnosis and prognosis. This book will be an essential companion to assist interventional cardiologists in better assessing patients with Coronary Artery Disease. It will encompass and review all interventional imaging modalities and provide guidance for interventional cardiologists to use these modalities.
The prevalence of autoimmune diseases and rheumatic conditions is constantly increasing. Autoimmune diseases affect approximately 7-10% of the population of the United States, while more than 50,000,000 American adults suffer from some type of arthritis. The Heart in Rheumatic, Autoimmune and Inflammatory Diseases examines the complex mechanisms relating to cardiac diseases from a pathophysiological and clinical point of view. Autoimmune rheumatic diseases can affect the coronary vessels, myocardium, pericardium, heart valves and the conduction system. The diagnosis of these unique cardiac complications necessitates medical awareness and a high index of suspicion. Increased risk of advanced atherosclerosis plays a pivotal role in the development of cardiac diseases in systemic, rheumatic and autoimmune illnesses. Yet, other complex immune medicated mechanisms may contribute to the pathogenesis. Patients' optimal care requires coordination between the primary caregiver, the rheumatologist, immunologist and cardiologist. Screening for cardiovascular risk factors, recognition of high-risk patients and identification of subclinical cardiac conditions are of great importance. Moreover, regulation of inflammation, as well as abnormal immune responses and the initiation of early treatments should be the focus of patient management. A continuous attempt to identify novel therapeutic targets and change the natural history of the underlying disease and its cardiac manifestations is in progress. The book aims at providing the readers with a state of the art collection of up to date information regarding clinically important topics based on experts' perspectives. This book was a result of an extended coordinated collaboration of one-hundred and fifty-four distinguished scientists from thirty-one countries around the globe. A review of common, as well as unusual (yet clinically significant) medical cardiac complications of prevalent rheumatic, autoimmune and inflammatory diseases. Focuses on aspects of pathophysiological processes, clinical presentations, screening tests, prognostic implications and novel therapeutic approaches. Presents an up-to-date “level of evidence” and “strengths of recommendations” for suggested therapies and reviews all randomized clinical trials, meta-analyses and other supporting published clinical findings.
