Neurocardiology is the study of the neurophysiological, neurological and neuroanatomical aspects of cardiology, including the neurological origins of cardiac disorders. The effects of stress on the heart are studied in terms of the heart's interactions with both the peripheral nervous system and the central nervous system. Clinical issues in neurocardiology include hypoxic–ischemic brain injury, neurogenic stress cardiomyopathy, cerebral embolism, encephalopathy, neurologic sequelae of cardiac and thoracic surgery and cardiac interventions, and cardiovascular findings in patients with primary neurological disease.
Overview Neurocardiology refers to study of the pathophysiological interactions between the nervous and cardiovascular systems. The communication between the heart and the brain have proved invaluable to the interdisciplinary fields of neurological and cardiac diseases. The fundamental understanding of the communication between the heart and the brain via the nervous system has led scientists towards an understanding of its elaborate circuitry. The brain emits neurological signals of oscillating frequencies. The neural rhythms provide information on the steady-state conditions of healthy individuals. Variations in the neural rhythms provide evidence that a problem is present regarding physiologic regulation and help physicians to more quickly determine the underlying condition based on the given symptoms. The neurocardiac axis links the cardiovascular and nervous systems to physiological problems such as arrhythmias, epilepsy and stroke. These problems are related to the fundamental factor of stress on the body. As stated previously, the changes in neural oscillations can contribute to the knowledge of what a steady state in an individual looks like, especially because it changes based on the person, as well as contributing to the imbalance of the nervous system and physiological function. Moreover, the brain can control the heart rate through the sympathetic nervous system.
Map between cardiovascular system and nervous system The cardiovascular system is regulated by the autonomic nervous system, which includes the sympathetic and parasympathetic nervous systems. A distinct balance between these systems is crucial for the pathophysiology of cardiovascular disease. An imbalance can be caused by hormone levels, lifestyle, environmental stressors and injuries. The complicated link between the brain and the heart can be mapped out from the complex of higher nervous system influences descending down to the heart. This complex innervates key autonomic structures from the brain's cortex to the heart along the neurocardiac axis. The heart is both the source of life and a source of cardiac arrhythmias and complications. The information originates in the brain's cortex and descends down to the hypothalamus. The neural signals are then transferred to the brainstem, followed by the spinal cord—the location from which the heart receives all its signals. In further detail, the heart receives its neural input through parasympathetic and sympathetic ganglia and the lateral grey column of the spinal cord.
Problems The neurocardiac axis is the link to many problems regarding the physiological functions of the body. This includes cardiac ischemia, stroke, epilepsy, heart arrhythmias and cardiac myopathies. Many of these problems are due to the imbalance of the nervous system, resulting in symptoms that affect both the heart and the brain. The connection between the cardiovascular and nervous system has raised concerns in the training processes for medical students. Neurocardiology is based on an understanding that systems within the body are interconnected. When training within one specialty, doctors are more likely to associate patients' symptoms with their field. Without taking integration into account, doctors can consequently delay a correct diagnosis and treatment for the patient. However, by specializing in a field, advancement in medicine continues as new findings come into perspective.
Stress
Cardiovascular systems are regulated by the autonomic nervous system, which includes the sympathetic and parasympathetic nervous systems. A distinct balance between these two systems is crucial for the pathophysiology of cardiovascular disease. Chronic stress has been widely studied for its effects on the body, resulting in an elevated heart rate (HR), reduced HR variability, elevated sympathetic tone and intensified cardiovascular activity. Consequently, stress promotes an autonomic imbalance in favor of the sympathetic nervous system. The activation of the sympathetic nervous system contributes to endothelial dysfunction, hypertension, atherosclerosis, insulin resistance and increased incidence of arrhythmias. An imbalance in the autonomic nervous system has been documented in mood disorders; it is commonly regarded as a mediator between mood disorders and cardiovascular disorders. The hypothalamus is the part of the brain that regulates function and responds to stress. When the brain perceives environmental danger, the amygdala fires a nerve impulse to the hypothalamus to initiate the body's fight-or-flight mode through the sympathetic nervous system. The stress response starts with the hypothalamus stimulating the pituitary gland, which releases the adrenocorticotropic hormone. This signals the release of cortisol, the stress hormone, initiating a multitude of physical effects on the body to aid in survival. A negative feedback loop is then needed to return the body to its resting state by signaling the parasympathetic nervous system. Prolonged stress leads to many hazards within the nervous system. Various hormones and glands become overworked, and chemical waste is produced, resulting in the degeneration of nerve cells. The result of prolonged stress is the breakdown of the body and the nervous system. Stress alone does not produce potentially deadly arrhythmias in normal healthy hearts; however, studies do appear to show that stress causes cardiac damage that may lead to arrhythmias.
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