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Key Words. postural tachycardia, autonomic disorder, POTS, chronic fatigue, syncope, orthostatic hypotension
Episodic periods of transient neurocardiogenic hypotension and bradycardia have become wellestablished cause of recurrent syncope and near syncope. Over the last decade tilt table testing became widely employed as a useful tool for diagnosing these disorders while at the same time provided a controlled environment for observation and measurement to be made [1]. During the virtual explosion of research that followed it was noted that these episodic disturbances in autonomic nervous system tone could result in varying degrees of systemic hypotension. While these falls in pressure might not be sufficiently great so as to allow for loss of consciousness, they were none the less enough to produce states of hypoperfusion sufficient to cause symptoms such as lightheadedness, vertigo, near syncope and focal neurologic defects that resembled transient ischemic attacks. During this same period a number of researchers became aware of a large subgroup of patients who exhibited a less severe form of autonomic disturbance causing a form of orthostatic intolerance characterized by postural tachycardia, disabling fatigue, exercise intolerance, blurred vision, lightheadedness, and dizziness [2]. Careful analysis of these patients revealed that their clinical histories, physical findings and responses to postural change and head up tilt were remarkably similar. The combined observations of multiple investigators found that these patients suffer from a distinct disorder which is most commonly referred to as the postural orthostatic tachycardia syndrome. The following review is designed to acquaint the interested reader with the clinical features of this condition, it's diagnosis and potential management options.
Physiologic Aspects
In order to understand this disorder it is necessary to brie[empty set]y review some aspects of the human body's mechanisms for adapting to postural orthostatic challenge. These are principally mediated via the autonomic nervous system.
The human nervous system has two basic components: The central nervous system, made up of the brain and the spinal cord [3]; and the peripheral nervous system, which is comprised of groups of neurons that are termed ganglia, and of peripheral nerves that lie outside the brain and spinal cord. Although anatomically separate, the two systems are functionally interconnected. The peripheral nervous system is further divided into somatic and autonomic divisions. The somatic division is principally concerned...