The clinical presentation of a patient with Postural Orthostatic Tachycardia Syndrome
(POTS) can not only be challenging but at times frustrating. For Physical Therapists
POTS is a relatively new diagnosis. It is commonly diagnosed in conjunction with other
pathology such as: Migraine, cervical pain, dizziness, imbalance/dysequilibrium and
Chronic Fatigue Syndrome (CFS). There are several reports suggesting that there may be
a great deal of overlap between POTS and CFS. 1 The purpose of the paper is to introduce
the pathophysiology of the condition and basic management principles.
To better understand the pathophysiology of POTS, a brief discussion of the Autonomic
Nervous System (ANS) is necessary. The ANS is divided into three subsystems: the
Sympathetic Nervous System (SNS), the Parasympathetic Nervous System (PNS), and
the Enteric Nervous System (ENS). The SNS is active for emergency situations such as
the “fight or flight” response. The SNS is responsible for producing bodily responses
such as pupil dilation, increase in heart rate, reduction in digestive function and increase
in conversion of glycogen to glucose. The PNS is involved in non-emergency situations
that allow us to “rest and digest.” The PNS produces bodily responses such as pupil
constriction, reduction in heart rate, increased saliva production and digestion. The ENS
assists in control of the viscera (gastrointestinal tract, pancreas, and gallbladder.)
POTS by definition is the failure of the peripheral vascular system to appropriately
vasoconstrict under orthostatic stress. The body then attempts to compensate for this by
increasing the heart rate (tachycardia).2 The increase in heart rate is clinically defined as:
a heart rate increase of 30 beats per minute (bpm) or more from supine to the standing
position within ten minutes or less. Several authors believe that POTS represents the
earliest sign of autonomic dysfunction and that some patients (approximately 10%) later
progress into having autonomic system failure.3 Many of these patients also can be
misdiagnosed as suffering from Chronic Fatigue Syndrome. There are several reports
suggesting that there may be a great deal of overlap between these two disorders. 3
There are many suspected causes of POTS4 such as:
• Viral and/or bacterial infections
• Changes in blood volume (hypovolemia)
• Exposure to toxic chemicals
• Genetically inherited
• Damage to the vagus nerve (cranial nerve ten) or spinal cord
• Spinal canal stenosis particularly in the upper cervical spine
• Diabetes
• Alcoholism
• Chiari I malformation
The hallmark of this syndrome is persistent/recurrent tachycardia while upright. This can
be associated with severe fatigue, near syncope or syncope, exercise intolerance,
lightheadedness or dizziness.4 Patients may complain of always feeling cold, while at
the same time they are unable to tolerate extreme heat. Stomach discomfort is common
because digestion can be effected. When the brain does not receive adequate blood
circulation it will shunt blood away from the stomach creating digestive difficulties.
Shortness of breath, memory disturbances, blurred vision, lower extremity paresthesia,
sweating and vertiginous episodes when transitioning from lying to standing and eye pain
with a feeling of pressure behind the eyes.
Another important characteristic of POTS is low blood pressure (although this is not a
requirement, some patients can have hypertension). The presence of low blood pressure
does not impact intelligence, but does impact a person’s ability to think clearly and
concentrate. The effect on concentration is usually intermittent and brief and is related to
the amount of blood getting to the brain. The reason that people have dramatic changes
in their heart rate is their body is attempting to compensate for the drop in their blood
pressure by increasing the heart rate. The increased stress on the heart is one of the
reasons why POTS patients complain of significant fatigue and a general feeling of being
“washed out.” The severity of a patient’s symptoms will vary. Some patients with POTS
can feel perfectly normal and have few symptoms. 5 At other times symptoms can be so
severe patients are forced to lie down for the entire day unable to function. POTS is a
chronic disease that often waxes and wanes but is always present to some extent on a
daily basis.
The pathophysiology of POTS can be described in simpler terms. Consider the human
body as a fluid filled bag, when lying supine the fluid is evenly distributed throughout.
Upon rising from supine to standing there is a gravity induced downward displacement of
approximately 25-30% of the blood volume (fluid) to the abdomen and dependent
extremities.6 Up to 50% of this displacement occurs within the first few seconds of
standing.6 This rapid redistribution of central blood volume (fluid) reduces the venous
return to the heart (cardiac filling pressure). The heart can not pump what it does not
receive, so the stroke volume (amount of blood the heart pumps) declines approximately
40%.7 The result is a reduced amount of blood volume to the brain and production of the
numerous symptoms previously listed. The SNS attempts to respond immediately to
these changes by:
1. Increasing the heart rate (tachycardia)
2. Increasing the force of the heart’s contractions.
3. Dilation of blood vessels in the lower extremities.
The medical management of POTS is pharmacologically designed medication intended to
regulate blood pressure and normalize blood volume. Diagnostics such as head upright
tilt (HUT) table testing may be performed prior to prescribing these medications. The
HUT is a passive orthostatic stress test used to evoke autonomic reflexes and vascular
responses. The patient is secured supine on a table that slowly elevates to an angle
between 60-90 degrees from horizontal for 10-45 minutes. The physiological response to
this positional change is closely monitored. Clinically, the HUT table test is not
particularly accurate due to a significant number of false positives (symptoms produced
during the test but are not true POTS) produced with this test. 8
There are a number of non-pharmacological treatments that have low risk and
considerable potential benefits. Increasing salt intake is often the safest first method to
try to improve orthostatic tolerance. (A high salt diet should only be tried under the
recommendation and supervision of a Physician). Adding extra salt to your diet will
increase your blood volume and blood pressure by increasing fluid retention (benefits are
variable and may only be transient). Patients suffering from POTS often have a
measurably reduced blood volume (hypovolemia). Increasing fluid intake is necessary
for the salt to expand the blood volume. This usually occurs spontaneously as salt
increases thirst. The use of supportive stockings may help reduce the pooling of blood
into the lower extremities while standing. Increasing lower extremity muscle tone has a
similar effect on reducing blood pooling and venous dilation. A patient with severe
symptoms may find any amount of exercise difficult however; slow progressive increases
over time can improve exercise tolerance. A Physical Therapist can design a program to
meet the specific needs of this patient population.
The following suggestions/tips may assist in managing symptoms related to POTS:
1. Avoid eating heavy meals. Overloading the stomach decreases orthostatic
tolerance by drawing blood to the digestive tract and away from the main arteries
that feed the brain.
2. During the day it is better to rest in a recliner chair rather than lying flat in bed
since. Constant bedrest decreases your orthostatic tolerance. An example of this
can be seen in the astronauts. Astronauts often develop a temporary form of
orthostatic tachycardia (rapid heart rate) upon returning to earth due to the
deconditioning effect of weightlessness, which is quite similar to prolonged
bedrest. Exercising can be done even when lying in bed by isometrically
contracting, and then relaxing the muscles in the arms and legs. It is very difficult
to regain muscle mass once it is lost therefore, it is very important to avoid
becoming deconditioned.
3. Avoid working with your arms over your head, lifting heavy objects, and
climbing stairs. Take frequent rest breaks and/or ask for assistance.
4. Warm temperatures can have a negative effect on their exercise tolerance. Heat
dilates blood vessels and diverts blood to the skin, thus reducing blood flow in
key arteries that feed the brain. Air conditioning in warm weather is essential,
especially when exercising.
Many POTS patients have little success and considerable frustration in attempting to get
relief for their symptoms. Dr. Blair Grubb9 from the Medical College of Ohio has an
interesting way of explaining the frustration of treatment for this condition. “Think of
your brain like the thermostat in your home, once it is set, it automatically maintains that
temperature and you no longer have to think about it. But if the furnace was not putting
out the heat needed to keep the home at that set temperature you would think something
was wrong with the furnace because all you know is that you are cold. If the repairman
came in and checked your furnace he would find that it is working normally. The reality
is the repair person (or medical specialist) has to understand the heating system well
enough to know to also check the “thermostat” (control center). Most importantly he
would then have to know how to fix the “thermostat”. This is an interesting analogy
because most physicians just want to try to fix the furnace; that is all they have been
trained to do. They may never give much thought to the “thermostat” (control center). It
can be very difficult to find healthcare providers trained to understand and manage the
whole problem. This is why many patients with POTS are frustrated and never truly
experience a therapeutic resolution.
POTS is an entity of varied etiologies and until a better understanding of the
pathophysiology is achieved, treatments are essentially empirical. Fortunately, ongoing
research is being conducted and treatment protocols continue to develop.
References
1. Bou-Holaigh I, Rowe P, Kan J, Calkins H. The relationship between neurally
mediated hypotension and chronic fatigue syndrome. JAMA. 1995; 274: 961-
967.
2. Hoeldtke RD, Danis KM. The orthostatic tachycardia syndrome: Evaluation
of autonomic function. J Clin Endocrinol Metab. 1991; 73:132-139.
3. Schondorf R, Low P. Idiopathic postural orthostatic tachycardia syndrome:
An attenuated from of pandysautonomia? Neurology. 1993; 43:132-137.
5. Steward J. Orthostatic Intolerance: An Overview. Emedicine.
(www.emedicine.com/ped/topic2860.htm). 2003; 1-18.
6. Shepherd JT, Sheperd RFJ. Control of the blood pressure and circulation in
man in Bannister R, Mathias C (eds). Autonomic Failure: A textbook of
Clinical Disorders of the Autonomic Nervous System. Oxford Medical
Publishers, Oxford UK 1992; 78-93.
7. Hainsworth R. Physiology and pathophysiology of syncope in Kenny R (ed).
Syncope in the older patient. Chapman and Hall Medical Publishers. London
UK 1996, pp 15-31.
8. Leonelli FM, Wang K, Evans JM: False positive head-up tilt: hemodynamic
and neurohumoral profile. J Am Coll Cardial 2000 Jan; 35(1): 188-93
{Medline}.
9. Grubb BP. Associate Professor of Medicine and Pediatrics; Division of
Cardiology and Neurology. The Medical College of Ohio.
