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Definitions | History | Symptoms | Management | Prognosis


It is estimated that over 500,000 Americans are afflicted with Orthostatic Intolerance. Despite the enormity of the number, these conditions are among the least understood of the autonomic disorders.

Affecting predominately younger individuals, often in those under the age of thirty five, these syndromes affect more women than men. The onset can be sudden, and the impact can be significant on both lifestyle and on the capacity to work.

Often, these conditions tend to be misdiagnosed as either a psychiatric or anxiety - related disorders, due to the nature of the symptoms.

Standing upright results in a series of reflexive bodily responses, regulated by the Autonomic Nervous System, to compensate for the effect of gravity upon the distribution of blood. These conditions are a result of an inappropriate response to this change in body position.

The normal response for a change in body position, results in a stabilization to the upright position in approximately sixty seconds. During this process, the normal change in heart rate would include an increase in heart rate of 10 to 15 beats per minute, and an increase in diastolic pressure of 10 mm Hg, with only a slight change in systolic pressure.

For those who are afflicted with Orthostatic Intolerance, there is an excessive increase in heart rate upon standing, resulting in the cardiovascular system working harder to maintain blood pressure and blood flow to the brain.

Upright posture also brings about a neurohumoral response, involving a change in the levels of vasopressin, renin, angiotensin and aldosterone levels - all of which are involved in the regulation of blood pressure.

Additionally, arterial baroreceptors, particularly those in the carotid sinus area, play an important role in the regulation of blood pressure and the response to positional changes. As the heart pumps blood to the body, the left atrium is passively filled with blood as a result of the force exerted by venous blood pressure. The baroreceptors in the left atrium respond, proportionately, to the pressure exerted by this venous blood pressure. Thus, a drop in venous blood pressure will trigger a compensatory response to increase blood pressure.

Any disruption in any of these processes, or their coordination, can result in an inappropriate response to an upright position, and can lead to a series of symptoms, and may include syncope.


The inappropriate response to an upright position has been observed and given a variety of names in medical literature. These names have included:

  • Soldier's Heart

  • Irritable Heart

  • Neurocirculatory Asthenia

  • Partial Dysautonomia

  • Hyperadrenergic Orthostatic Hypotension

  • Vasoregulatory Asthenia

Currently, there are three main categories used to describe Orthostatic Intolerance Conditions:

  • Postural Tachycardia Syndrome (POTS)

  • Mitral Valve Prolapse Dysautonomia

  • Idiopathic Hypovolemia

These conditions are similar in presentation, and in the ensuing treatment plans. The underlying mechanisms will have to become better understood in order to alleviate some of the overlap in the terminology used for these conditions.

Individualized treatment plans are often necessary to manage these conditions.


The symptoms for these conditions may include the following:

  • Excessive Fatigue

  • Exercise Intolerance

  • Recurrent Syncope or Near Syncope

  • Dizziness

  • Nausea

  • Tachycardia

  • Palpitations

  • Visual Disturbances

    • Blurred Vision

    • Tunnel Vision

    • Graying Out

  • Tremulusness

  • Weakness - most noticeable in the legs

  • Chest Discomfort

  • Shortness of Breath

  • Mood Swings

  • Migraines and Other Headaches

  • Gastrointestinal Problems


There has been much new insight gained as to the mechanisms of these disorders in the past several years, and as a result, it can be confusing for both the affected individual, as well as the physician, to get a clear understanding of these conditions, and how to effectively manage them.

As a result, management of these conditions needs to be highly individualized, and may include both pharmocologic and non-pharmocologic methods.


The majority of individuals affected with Orthostatic Intolerance Syndromes see an improvement in their condition, and only experience mild symptoms. However, for some, the disorder can be a debilitating condition, that poses a significant challenge for effective treatment. Additional research into the underlying causes of these disorders will be necessary to develop more effective treatment plans.

For many, the effect of these disorders will be short lived, while others tend to show a progressive nature to their disorder, and a worsening of symptoms may occur.

In most cases, a well defined, individualized, treatment plan needs to be developed. Since the underlying causes for these disorders are not yet completely understood, no one approach can be defined as the sole treatment plan. The underlying causes for these disorders are probably multiple, and, for some, may include an underlying autonomic nervous system disease.

Continued research into these disorders will result in more effective diagnostic tools and treatment plans.


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The National Dysautonomia Research Foundation (NDRF) has established this site to help inform afflicted patients, physicians and the general public on the various forms of Dysautonomia. It is our desire to give timely, as well as, accurate information, however NDRF will not be responsible for the misinterpretation of the information provided.  Questions or problems regarding this web site should be directed to .

Medical questions and information, should be reviewed with your physician. 

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Last modified: Monday January 28, 2008.