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Upright tilt testing was devised in the
1940's at NASA as a postural stressor and its use in cardiology as a test for
fainting and related disorders dates from the 1980's. In the young it is
neither specific nor sensitive and to improve these indices workers have
combined the test with pharmacological agents whose use is moot. However, as an
orthostatic stress test that [mostly] disables the skeletal muscle pump it is
excellent. Note that tilt is not exclusively a test of the autonomic nervous
system but is instead an orthostatic stressor which evokes compensatory
responses among them autonomic responses.
Patients with orthostatic
intolerance and in particular those with syncope (fainting) are
often referred early during their evaluation to a cardiologist.
The reason is that cardiac disease ranks high on the list of
dangerous illnesses which provoke syncope although rarely chronic
orthostatic intolerance. Typically, this form of syncope is not
posturally induced but occurs in all positions. While most
children and adolescents with syncope or orthostatic intolerance
do not have cardiac disease, our first task is to rule out heart
disease. Therefore a cardiac examination along with pertinent
laboratory screening tests are often required and may include
electrocardiography, echocardiography (cardiac ultrasound) to
rule out structural heart disease, and event monitoring using
transtelephonic devices to rule out important arrhythmias which
often are the immediate precipitant for cardiac syncope. In
addition a good neurologic examiniation is important and may also
include some tests. Blood sampling often includes a complete
blood count with leukocyte differential; erythrocyte
sedimentation rate, serum levels of alanine aminotransferase,
total protein, albumin, globulin, alkaline phosphatase, calcium,
phosphorus, glucose, blood urea nitrogen, electrolytes,
creatinine, thyroid-stimulating hormone, urinalysis., and a
pregnancy test in girls.
Once cardiac and other diseases
are ruled out, neurovascular diagnosis is necessary.
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