This is another form of provocative testing intended to
reproduce the circumstances leading to a fainting episode.
As described in the section on syncope, the most common
form of loss of consciousness is referred to as neurocardio-
genic syncope. In addition to this, other forms of primary
postural hypotension can be diagnosed using the Head up tilt
test. In theory, when a patient is undergoing continuous arterial
pressure monitoring and brought to the upright posture, there is
a degree of pooling of venous blood into the dependent portions
of the body. In the susceptible individual, a critical degree of
pooling can result in a drop in venous return to the extent that
a reflex is initiated leading to syncope. As in the case of EPS,
if the test is associated with the production of hypotension,
it is presumed to represent what has previously happened to
the patient. Typically, the patient is firmly secured to a table
after introducing an indwelling arterial catheter for the purpose
of measuring continuous intra-arterial pressure. The procedure
can be done with a traditional cuff, but important ancillary infor-
mation can be missed. The patient is brought to a 60-80 degree
angle until 20 minutes has elapsed or the patient begins to develop
hypotension and symptomatology.
Certain patterns of blood pressure reduction, with or without
associated heart rate changes, determine the type of response.
Once a specific type of disorder of blood pressure regulation is
diagnosed, a treatment plan can be instituted. Therapy includes
withdrawal of offending medications, increase sodium intake
(including salt tablet therapy) in patients without a history of
hypertension or heart failure, beta-blockers or other medications
that may act to directly raise blood pressure. Nonpharmacologic
approaches include avoidance of prolonged recumbence or upright
posture, lower extremity exercises, thigh-high support stockings
and stress management. The latter is particularly important since
many cases of new onset neurocardiogenic syncope are a manifest-
ation of stress.
In most individuals with new onset neurocardiogenic syncope, the
disorder is self-limited and eventually spontaneously subsides
without recurrence. This may take as long as several weeks to
months, however.
The sudden onset of rapid heart rhythms or tachycardias is the
second most common cause of syncope. These are discussed in
the following sections. The reason for a drop in blood pressure
accompanying sudden onset of tachycardia is related to the
marked decrease in the opportunity for the heart to fill with
blood to make the next beat a full volume pulse. This is in
contrast to slow heart rhythm problems (bradycardias), which
do not cause a drop in blood pressure.
In most instances, the cause of syncope can be diagnosed from
the facts provided by the history alone. When in doubt or if under-
lying heart disease is suspect based upon the patients known past
medical history, an echocardiogram is often the most useful tool
to clarify whether structural heart disease exists. When present,
it may be necessary to perform electrophysiologic testing in order
to exclude the presence of an underlying serious rhythm disturbance.
Electrophysiologic testing and Head up tilt testing is also useful as
a confirmatory measure when the diagnosis is in doubt. In some
instances, either external or implantable event recorders can
be helpful.
Please click name, for information regarding the following
diagnostic tests.
