Chronic Orthostatic Intolerance

Up ] Physiology of Orthostasis ] Patterns of Orthostatic Intolerance ] Acute Orthostatic Intolerance and Syncope ] [ Chronic Orthostatic Intolerance ]


POTS and Chronic Orthostatic Intolerance ] Chronic Fatigue Syndrome ]

Postural Orthostatic Tachycardia Syndrome (POTS), the Chronic Fatigue Syndrome (CFS) and Post-Inflammatory Fatigue
Symptoms include lightheadedness or dizziness (in all patients) associated with pallor, exercise intolerance and fatigue in most, blurred vision, chest discomfort, shortness of breath or hyperpnea, palpitations, tremulousness, clamminess, anxiety, nausea/abdominal pain while standing, acrocyanosis, weakness (which must be related to a loss of postural tone), headache (which must be provoked by orthostasis), flushing, neurocognitive defects and sleep impairment. Associated findings are mitral valve prolapse, and gastrointestinal illness including irritable bowel disease. A subgroup of mitral valve prolapse patients are known to have autonomic dysfunction including a hyperadrenergic state  while abnormal serotoninergic pathways are one source of neuro-intestinal dysfunction in irritable bowel disease.The relationship of symptoms to orthostasis is a key aspect of orthostatic intolerance although some patients may experience symptoms during sitting as well as while standing. Therefore history taking is critical. Usually a long-standing history of symptoms (on the order of 3 or more for 3-6 months) is necessary before the diagnosis of chronic orthostatic intolerance should be confirmed.

Chronic orthostatic intolerance occurs with chronic failure of the autonomic nervous system as in primary autonomic failure, multiple system atrophy, and secondary autonomic failure in diabetes and Parkinsonism, but, with the exception of familial dysautonomia, these are rare events in children.  

However, evidence for extensive involvement of orthostatic intolerance diagnosed by HUT has recently been described in a syndrome of postural tachycardia (POTS) characterized by symptoms of orthostatic intolerance in association with a rapid heart rate when upright. Some patients have severe hypotension. Patients run the gamut from minimally affected to seriously disabled. Adolescents with the Chronic Fatigue Syndrome (CFS) almost all have a variant of POTS which has also been noted in attenuated form during post-inflammatory illnesses such as the post-Lyme syndrome endemic to our area. Our preliminary data in adolescents and the work of others have shown a form of orthostatic intolerance with uniquely abnormal neurovascular physiology related to other forms of orthostatic intolerance. Indeed, the only effective treatment for CFS in adults and children seems to target orthostatic intolerance. The cardiovascular form taken by OI in these syndromes is distinct in producing low blood pressure without overt fainting but with severe, often disabling postural symptoms associated with tachycardia. Data suggest a post-inflammatory mechanism involving abnormality in venous blood flow returning to the heart and resulting in a hypovolemic state (low blood volume) not unlike hemorrhage. 


We found evidence for defective vasoconstriction and vascular pooling in these patients, in which purplish discoloration and swelling of the legs occur (see figure). This is particularly obvious in those with the worst clinical symptoms. Although these problems are described in adults, little is known concerning its diagnosis and treatment in children, particularly in teenagers.


 Circulatory Findings in POTS


Physiology of Orthostasis
Patterns of Orthostatic Intolerance
Acute Orthostatic Intolerance and Syncope
Chronic Orthostatic Intolerance