Branko Furst - The Heart and Circulation: An Integrative Model

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Traditional models of the human circulation based on the generation of pulsatile flow into a coupled viscoelastic arterial system have evolved since man first had the opportunity to observe the movement of blood in mammals. These models are capable of explaining and modeling most of what we observe as clinicians much as Newtonian physics explains what we observe in the physical world around us. It is only when someone, as Branko Furst, M.D., has done in this tome, delves deeper into circulatory phenomena that are not so readily observed that we have cause to question the adequacy of the pressure-propulsion model of circulation. I liken the effort made by Dr. Furst here to the use of quantum and string theory to explain phenomena not readily explainable by classic Newtonian physics. There is much about the human circulation that remains mysterious, and in this brilliant work the author has opened our eyes to the necessity of developing a unifying model of the human circulation that can explain all observed phenomena. This book is a must read for anyone interested in the intricacies of the human circulation beyond what can be causally observed.

The cardiovascular system is complicated. However, frequently it is presented as a pump (the heart) that delivers fluid into a series of pipes (blood vessels) of varying resistance. The relationship between the output of the pump and the resistance in the pipes then determines the driving pressure (mean arterial pressure), which distributes the fluid (blood) around the system. This simple fluid engineering model is then supplemented or expanded by ideas about how various elements of this system are controlled. All of this thinking leads perhaps to what might be described as a cardiocentric view of the cardiovascular system. This cardiocentric view is reinforced by the dramatic events like death that occur when the pump stops for any one of a number of reasons.

In this monograph Branko Furst raises a number of interesting points about the oversimplified view outlined above.

First, how many pumps are there in the cardiovascular system? One could argue that there is the heart itself, the skeletal muscle pump which returns blood from the periphery to the central circulation and can translocate a large volume of blood in a matter of seconds. Perhaps there is a third pump embedded in the large elastic arteries that stores energy after cardiac systole and uses elastic recoil to propel the blood forward? If there is more than one pump, how do they operate together to deliver and return blood flow to the peripheral organs?

Second, the heart is seen largely as a pump, but both old and new ideas suggest that the twisting motions associated with cardiac ejection lead to a sucking action during cardiac relaxation. How much does this sucking action contribute to the filling of the heart and the subsequent delivery of blood to the periphery?

Third, the heart, blood vessels, and peripheral tissues all contain sensory nerve endings that influence cardiovascular function. Just like there is a so-called enteric nervous system, is there a cardiovascular nervous system?

Fourth, in addition to these pumps and the neural network that governs the cardiovascular system, there are a host of local control mechanisms that are too numerous to catalog in this introduction. For example, metabolites released by contracting skeletal muscle can evoke local vasodilation on a scale (50- to 100-fold) that is difficult to imagine. What factors contribute to this and how does the rest of the system respond to it?

Fifth and finally, there is the problem of cardiovascular disease. The traditional view of cardiovascular disease is that it is mostly a pump problem or blood vessel problem. However, diseases like heart failure and hypertension are in fact systemic, and a variety of feedback control mechanisms alluded to above become hijacked over time to reinforce the pathophysiology as opposed to correcting it.

These and other topics, including where the ideas behind various pieces of current dogma came from, are discussed in this book. So, we learn the history of the dogma, the limitations of the dogma, and a variety of altered perspectives that will help students, physiologists, and physicians to think about the cardiovascular system in a more nuanced and functional way. Like all good scientific and medical thinking, asking the right question is ultimately more important than simply mastery of current ideas, and this book is full of the right questions or ideas that will lead the reader to their own right questions.

Despite remarkable progress in medical treatment within the last 10 years, morbidity and mortality of heart failure are still high: 7080% of patients suffering from heart failure will die within the next 8 years. Paradoxically, the prevalence of heart failure remains high as more patients survive myocardial infarctions and fewer are dying from lethal arrhythmias. The traditional biological models used for understanding the cardiovascular function in failing hearts have been inconsistent and impeded the development of newer and more effective therapies. Some of these limitations may result from inaccuracies in modeling the structure and physiology of the cardiovascular system. In particular, the architecture and the working of cardiac chambers, which maintain the highly efficient global function of the normal heart, remain controversial and incompletely characterized.