Brain, Vol. 124, No. 3, 637-638,
March 2001
© 2001 Oxford University Press
Book reviews |
THE NERVOUS SYSTEM AND THE HEART.
Edited by Gert J. Ter Horst. 1999. New Jersey: Humana Press. Price $145. Pp. 584. ISBN 0-89603-693-6.
Department of Neurology, AZ Sint-Jan, Bruges, Belgium
In common language, the brain and the heart have been used as metaphors for thinking and feeling, for cognition and emotion. As a modern alternative, this book offers a scientific approach to the state-of-the-art knowledge about the complex relationship between these two organs. It does not deal with every aspect of the interrelationship between the heart and the nervous system, looking at these complex interactions mainly from the viewpoint of the heart and stressing the importance of knowledge in this domain for understanding cardiac function, physiology and disease. However, the heart–brain relationship in stroke, an important topic to the neurologist, is not discussed.
Chapter 1 describes the efferent and afferent nerve supply of the heart. It relies on studies in the pig, but also in humans. It reviews the neurotransmitters involved, both classical ones (noradrenaline and acetylcholine) and other neurochemicals (ATP, neuropeptide Y, VIP, somatostatin, substance P, CGRP, nitric oxide and others). The authors of this chapter emphasize the importance of the intrinsic intracardiac neurones in the effective control of cardiac performance.
Chapter 2 is written by the editor and concentrates on nervous circuitry controlling cardiac activity as part of emotional expression. First, a historical account of the neurobiology of emotion is given, briefly discussing the circuit of Papez and the limbic system. There is then a review of lesions, stimulation studies and neuroimaging in humans, concluding that different neuronal networks mediate specific emotions. The role of the amygdala in fear and anger responses is stressed. An exhaustive review of fundamental research in the field of nervous circuitry for emotions and regulation of heart activity concludes that cardiovascular activity is regulated by a hierarchical system, in which the hypothalamus is functioning at the highest level of command.
Chapter 3 is devoted to the circadian organization of the autonomic nervous system. It describes the connections between the suprachiasmatic nucleus and the hypothalamus. The complex role of the neurotransmitters GABA and vasopressin is described nicely and the influence of the suprachiasmatic nucleus on the circadian rhythm of corticosterone secretion is also dealt with. Finally, some arguments are advanced for a direct influence of the suprachiasmatic nucleus on the autonomic nervous system, not limited to its influence on the pineal and the adrenal glands.
Dysfunction of the brain may underlie cardiac disease. Chapter 4 discusses the cardiovascular effects of neuropathological conditions in experimental animals. The studies suggest that the insular cortex plays a role in the tonic regulation of autonomic responses; moreover, they show a right-hemispheric dominance for sympathetic effects. The infralimbic cortex can also generate cardiovascular changes, mainly by inhibition of autonomic tone. The amygdala plays a major role in the integration of autonomic responses to emotional stimuli.
Chapter 5 reviews the clinical aspects of human neuropathology and cardiovascular regulation. The methods for assessing cardiovascular autonomic function are briefly described. Then, different cardiovascular complications are discussed, e.g. ECG changes and cardiac arrhythmias in cerebral lesions, autonomic dysfunction in Parkinson's disease, multiple system atrophy, multiple sclerosis, migraine and peripheral neuropathies.
Chapter 6 attempts to give a recent view on the hypothalamopituitary–adrenal system, stress and the heart. It is most likely that the hormones involved (corticosteroids, CRH and melanocortins) play a modulatory role in stress, both in the brain and at the heart level.
The cardiac nociceptive system is dealt with in Chapter 7. Angina pectoris pain is described as a visceral pain involving intrinsic cardiac neurones, mediastinal ganglia, the spinal cord and brain areas. The role of lactate, bradykinin, potassium, substance P and serotonin is reviewed. Only adenosine is released in substantial quantity during myocardial ischaemia and is able to excite cardiac nerves and provoke anginal chest pain. Silent myocardial ischaemia and syndrome X are considered manifestations of an alteration of the cardiac nociceptive system.
Chapter 8 is illuminating. It stresses the differential representations of deep and superficial pain, as already hypothesized by Sir Thomas Lewis in 1942. Based on elegant studies in the rat, using immediate-early gene expression as a marker of neuronal activation, the authors consistently show that there is a clear separation between superficial and deep pain at the spinal cord level; cardiac pain activates neurones in the same spinal laminae as other types of deep somatic/visceral pain. Significant activation of upper cervical cord neurones occurs after noxious stimulation of the heart. The role of the nucleus of the solitary tract in central deep pain conduction remains controversial.
Chapter 9 is very short, discussing the neurophysiology of heart pain. Alas, it does not integrate the anatomical data from the previous chapter and gives a rather superficial survey of the subject.
In Chapter 10, Stuart Rosen reviews his studies of PET scanning in angina pectoris, silent ischemia and syndrome X. He concludes that in patients with coronary heart disease, the central structures activated in angina pectoris, but not in silent ischemia, constitute the pathways involved in the perception of heart pain; consequently, the thalamus may have a central role in the perception of pain from the heart. In syndrome X, there is an abnormal activation of the right insula, pointing to a `visceral cortical pain syndrome' mechanism and, thus, to a cerebral—not cardiac—origin of the symptoms.
Chapter 11 focuses on the central renin–angiotensin system in the regulation of body fluid and cardiovascular homeostasis. Synthesis of angiotensin II has indeed been demonstrated clearly in the brain. The renin–angiotensin system produces pressor responses through activation of peripheral and central angiotensin II receptors. Furthermore, angiotensin II exerts tonic inhibitory control over baroreceptor reflex activity. The central renin–angiotensin system contributes to the development and maintenance of arterial hypertension in the spontaneously hypertensive rat.
Chapter 12 reviews the role of mediators of inflammation in patients with coronary artery disease. It concludes that, besides the classical risk factors influencing atherogenesis, both a systemic and a local inflammatory response to either a systemic infection or an autoimmune reaction may induce atherosclerosis. Reduction of the inflammatory response could lead to plaque stabilization.
Finally, Chapter 13 is dedicated to the relationship between heart disease and cognitive/neuropsychiatric disorders. There is convincing evidence that depression and cardiovascular disease are linked in both ways. Moreover, it is not the type A behaviour pattern (hard driving, workaholic) that predisposes to heart disease, as was formerly thought, but the type D (distressed to depressed) personalities. The relationship between anxiety disorders and cardiovascular disease has been less extensively studied and is briefly summarized. Research regarding cognitive disorders in heart patients is scarce.
Overall, the book is something of a mixed bag: it offers very interesting insights on different topics but lacks unity. Most chapters are comprehensive, well written and give an up-to-date survey of the discussed topic; those on circadian organization of the autonomic nervous system, on the neuroanatomy of cardiac nociceptive pathways and on neuroimaging of heart pain are excellent and enlightening. However, most chapters stand alone and do not elaborate on the contributions of co-authors in other chapters. There is also little cross-referencing between the chapters and the preface by the editor is only partly successful in its attempt to link the chapters together. The succession of the chapters does not always reflect a logical order; in my opinion, it would have been better to group the anatomical chapters at the beginning and the clinical ones at the end. The figures are numbered per chapter, which is somewhat confusing; adding the number of the chapter to the number of the figure would have been helpful. The references are thorough and complete, offering a welcome invitation to further reading and the index at the end of the book is also valuable.
In summary, this book offers a timely review of recent insights on different topics involving the influence of the nervous system on the heart in health and disease. It can be recommended to neurologists and neuroscientists interested in the heart–brain relationship, but especially to cardiologists wishing to put their organ of interest into a broader perspective.
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