This is an HTML version of an attachment to the Freedom of Information request 'Summary Minutes for CHM meeting on 16th & 17th July 2015'.

NIH Public Access
Author Manuscript
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.
NIH-PA Author Manuscript
Published in final edited form as:
J Cardiovasc Electrophysiol. 2009 March ; 20(3): 352–358. doi:10.1111/j.1540-8167.2008.01407.x.
Postural Tachycardia Syndrome (POTS)
Phillip A. Low, M.D.*, Paola Sandroni, M.D., Ph.D.*, Michael Joyner, M.D.†, and Win-Kuang
Shen, M.D.

*Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
†Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota, USA
‡Department of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester,
Minnesota, USA
Introduction—POTS is defined as the development of orthostatic symptoms associated with a
NIH-PA Author Manuscript
heart rate (HR) increment ≥30, usually to ≥120 bpm without orthostatic hypotension. Symptoms
of orthostatic intolerance are those due to brain hypoperfusion and those due to sympathetic
Methods—We provide a review of POTS based primarily on work from the Mayo Clinic.
Results—Females predominate over males by 5:1. Mean age of onset in adults is about 30 years
and most patients are between the ages of 20–40 years. Pathophysiologic mechanisms (not
mutually exclusive) include peripheral denervation, hypovolemia, venous pooling, β-receptor
supersensitivity, psychologic mechanisms, and presumed impairment of brain stem regulation.
Prolonged deconditioning may also interact with these mechanisms to exacerbate symptoms. The
evaluation of POTS requires a focused history and examination, followed by tests that should
include HUT, some estimation of volume status and preferably some evaluation of peripheral
denervation and hyperadrenergic state. All patients with POTS require a high salt diet, copious
fluids, and postural training. Many require β-receptor antagonists in small doses and low-dose
vasoconstrictors. Somatic hypervigilance and psychologic factors are involved in a significant
proportion of patients.
Conclusions—POTS is heterogeneous in presentation and mechanisms. Major mechanisms are
denervation, hypovolemia, deconditioning, and hyperadrenergic state. Most patients can benefit
NIH-PA Author Manuscript
from a pathophysiologically based regimen of management.
POTS; hypovolemia; denervation; deconditioning; orthostatic; hyperadrenergic state
Orthostatic intolerance is defined as the development of symptoms of cerebral
hypoperfusion or sympathetic activation while standing that is relieved by recumbency.
Patients with orthostatic intolerance often present with complaints of exercise intolerance,
lightheadedness, diminished concentration, tremulousness, nausea and recurrent syncope,
and may be incorrectly labeled as having panic disorder or chronic anxiety.1 Simple
activities such as eating, showering, or low-intensity exercise may profoundly exacerbate
Address for correspondence: Philip A. Low, M.D., Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Fax:

Low et al.
Page 2
these symptoms and may significantly impair even the most rudimentary activities of daily
living. Somewhat paradoxically, the magnitude of these symptoms is often significantly
NIH-PA Author Manuscript
greater than those observed in patients with obvious clinically detectable autonomic failure.
Although neurogenic orthostatic hypotension (OH) due to the autonomic neuropathies, such
as those of diabetes and amyloidosis, and nonneuropathic disorders such as MSA (multiple
system atrophy; Shy-Drager syndrome) and PAF (pure autonomic failure; idiopathic
orthostatic hypotension) are better known, these disorders are relatively uncommon. Most
patients with orthostatic intolerance do not have florid autonomic failure and do not have
OH. Improved recognition of lesser degrees of orthostatic intolerance came with the
observation that the most common and the earliest manifestation of orthostatic intolerance is
an excessive tachycardia.2 These subjects have disorders that are sometimes termed
“benign” disorders of reduced orthostatic tolerance. The unifying feature is the development
of orthostatic symptoms without consistent OH. Investigators and clinicians have been
impressed with different aspects of the conditions and have approached orthostatic
intolerance from different perspectives. Terms such as effort syndrome, neurasthenia,
idiopathic hypovolemia,3 sympathotonic orthostatic hypotension, emphasizing sympathetic
overactivity,4 and mitral valve prolapse syndrome5 exemplify the concentration on
particular components of the patient’s disease. Postural tachycardia ± syncope can be
present in several of the disorders. Some patients with chronic fatigue syndrome have
NIH-PA Author Manuscript
orthostatic intolerance with tilt-induced syncope, and a subset will respond to treatment
directed at syncope.6
We have focused on orthostatic tachycardia since an excessive HR increment appears to be
the earliest and most consistent of the easily measured indices of orthostatic intolerance.7
Most of the other terms focus on manifestations that are not consistently present. The term
idiopathic hypovolemia is unsatisfactory, since most patients do not have reduced plasma
volumes or red cell mass. Current thinking is that the occurrence of mitral valve prolapse
with POTS is fortuitous. The emphasis on postural tachycardia does, however, have a
disadvantage in that it ignores nonorthostatic symptoms such as paroxysmal episodes of
autonomic dysfunction, including sinus tachycardia, BP fluctuations, vasomotor (especially
acral) symptoms, and fatigue.
The prevalence of POTS is unknown. In clinical practice, it is probably about 5–10 times as
common as orthostatic hypotension. One estimate is the prevalence is at least 170/100,000.8
This is based on the investigators’ documentation that 40% of patients with chronic fatigue
syndrome have POTS.
NIH-PA Author Manuscript
Clinical Features
The age of presentation is most commonly between 15 and 50 years.9,10 Most patients that
we have evaluated have had the symptoms for about one year. The orthostatic symptoms
consist of symptoms of reduced cerebral perfusion coupled with those of sympathetic
activation. The most common symptoms are lightheadedness, palpitations, symptoms of
presyncope, tremulousness, and weakness or heaviness (especially of the legs). These
symptoms are commonly exacerbated by heat and exercise (Table 1). Other common
symptoms are shortness of breath and chest pain.11 The symptoms these patients experience
differ from those of patients with orthostatic hypotension in that there are significant
symptoms of sympathetic activation.12 There may be an overrepresentation of migraine,
sleep disorders, and fatigue, and fibromyalgia is sometimes associated.1 There is a clear
overrepresentation of women.11 We have found a consistent female:male ratio of 5:1.
Early studies suggested that approximately one-half of patients have an antecedent presumed
viral illness,1,13 although recent experience suggests that this is less common. Another
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 3
feature of POTS is the cyclical nature of the symptoms. Some females will have marked
deterioration of their symptoms at certain stages of their menstrual cycle associated with
NIH-PA Author Manuscript
significant weight and fluid changes. Typically, these patients have large fluctuations in
their weights, sometimes up to 5 pounds. Others have cycles of several days of intense
orthostatic intolerance followed by a similar period when their symptoms are less. Some
patients have episodic symptoms at rest associated with changes in BP and HR that are
unrelated to arrhythmias. The HR alterations are typically a sinus tachycardia, although a
bradycardia can occur.14 Fatigue can be a problem during these episodes. Some describe
periods when they have trouble retaining fluid, in spite of heavy intake. Studies of fluid
balance and antidiuretic hormone levels are not well documented. Orthostatic intolerance
with low BP requiring repeat visits to the emergency room for intravenous saline infusions
is uncommon but by no means rare.
Fatigue is commonly present.11 Patients complain of poor exercise tolerance with
physiological features including reduced stroke volume and reflex tachycardia typical of
subjects who are deconditioned, such as in persons who have had prolonged bed rest.15
Coupled with the poor exercise tolerance, an excessively long recovery cycle following
exercise is often described. Additionally, patients typically note that they have low energy,
even at rest. The sense of fatigue will sometimes occur in cycles and may last days or even
weeks and then lift.
NIH-PA Author Manuscript
Clinical examination reveals an excessive HR increment. Pulse pressure may be excessively
reduced and there is marked beat–to-beat variability of both pulse pressure and HR. One
clinical correlate is the difficulty in palpating a radial pulse with continued standing or with
the performance of a Valsalva maneuver (Flack sign). Another clinical sign is the
development of acral coldness. With continued standing, there may be venous prominence
resulting in a blueness and even swelling of the feet.7
Evaluation of Suspected POTS
All patients need a detailed history to document the severity of orthostatic intolerance, its
modifying factors and influence on activities of daily living. It is helpful to grade the
severity of orthostatic intolerance, based on symptoms, standing time, and effect on
activities of daily living (Table 2). A full autonomic system review should document
autonomic systems involved and whether there are symptoms to suggest an autonomic
neuropathy. Commonly associated disturbances such as fatigue, sleep disturbance, and
migraine should be documented.
NIH-PA Author Manuscript
HUT and Evaluation of Adrenergic Function
The evaluation of POTS is summarized in Table 3. Cardiovascular responses to HUT should
be done with continuous recordings of BP and HR for a minimum of 10 minutes. The HR
response in POTS varies from 120–170 bpm on HUT, and the patient typically attains these
values by 5 minutes. Orthostatic intolerance is present when HUT results in a HR increment
≥30 bpm and associated with symptoms of orthostatic intolerance in patients ≥18 years.
Sometimes the term mild orthostatic intolerance is used for patients who fulfill these criteria
but remain <120 bpm. A fall in BP beyond 10 minutes (delayed orthostatic hypotension)
occurs in about 40% of subjects and is associated with normal or near-normal adrenergic
function.16 The HR response may oscillate excessively. The BP responses occur in several
patterns. Patients with hypovolemia or excessive venous pooling may have an excessive
reduction in pulse pressure. Some have a hypertensive SBP response (hyperadrenergic
POTS (Fig. 1). Some patients have prominent fluctuations with increases in diastolic BP by
up to 50 mmHg, with large fluctuations.
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 4
Plasma catecholamines should be measured supine and after standing for 15 minutes. The
primary interest is in norepinephrine. In about half the patients standing, norepinephrine
NIH-PA Author Manuscript
exceeds 600 pg/mL, considered a hyperadrenergic response.11,14 A 24-hour urine sodium is
a simple and helpful test that provides documentation that the patient is taking sufficient
fluids and sodium. The goal is a volume of 1,500–2,500 mL and sodium excretion of 170
mmol/24 hours. The latter indicates that the patient is taking adequate sodium and likely has
a normal plasma volume.17
The beat-to-beat BP and HR responses to the Valsalva maneuver are abnormal in about half
the patients.12,13 The pulse pressure falls by more than 50% and may be obliterated. The
Valsalva maneuver provides an estimate of both the vagal and adrenergic components of
baroreflex sensitivity (BRS). By relating the fall in BP during phase II_E to heart period,
vagal BRS (BRS_v) can be calculated.18–20 Baroreflex unloading results in the adrenergic
component of the baroreflex with a rise in total peripheral resistance, manifested in the VM
as II_L, and phase IV. Since the duration of expiratory pressure is short (10–15 seconds),
II_L is not always generated and is often absent in normal subjects older than 60 years of
age. Hence, this is an unreliable index of adrenergic baroreflex sensitivity (BRS_a). Phase
IV is a better index but is subject to much variability. The most reliable index is BP recovery
time (PRT), defined as time from phase III to return to baseline (in seconds).20 BRS_a can
be better quantified by relating BRS_a to the preceding fall in BP.18,19
NIH-PA Author Manuscript
Some Varieties of POTS
A number of types of POTS have been described. The following is an abbreviated
description from a large review.10
Neuropathic POTS
A number of phenotypes have been described. Three phenotypes (Table 4) are sufficiently
well described. About half of patients with POTS have a restricted autonomic neuropathy
with a length-dependent distribution of neuropathy.11,13 The term length-dependent
neuropathy refers to one where the ends of the longer fibers are affected before the shorter
ones. Distal postganglionic sudomotor denervation can be demonstrated with the
quantitative sudomotor axon reflex test (QSART)21 or the thermoregulatory sweat test.22
These tests demonstrate sudomotor denervation to the foot and toes. Adrenergic impairment
to the lower extremity can be seen in neuropathic POTS demonstrable as impaired
norepinephrine spillover in the leg while the arm response remains normal.23 In the clinical
laboratory, we have used a practical index of adrenergic denervation. When BP recovery
time (PRT) ≥6 seconds in the age group of POTS, adrenergic denervation is likely.20
NIH-PA Author Manuscript
Support for the notion of neuropathic POTS comes also from the 1 in 7 patients who have
low titer of A3 acetylcholine receptor antibodies,11 a finding that suggests an autoimmune
attach of autonomic nerves.
Hyperadrenergic POTS
One subset of POTS is characterized by an excessive increase of plasma norepinephrine and
a rise of BP on standing.14,24 Hyperadrenergic POTS is defined as POTS associated with a
systolic BP increment ≥10 mmHg during 10 minutes of HUT, and an orthostatic plasma
norepinephrine ≥600 pg/mL (Fig. 1). These patients have similar HR increment to
nonhyperadrenergic POTS, but tend to have prominent symptoms of sympathetic
activation,24 such as palpitations, anxiety, tachycardia, and tremulousness. These patients
have a larger fall in BP following ganglionic blockade with trimethaphan, and higher upright
plasma norepinephrine levels than did nonhyperadrenergic POTS patients,24 presumably
indicating a major role of orthostatic sympathetic activation. Elevation of plasma
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 5
norepinephrine ≥600 pg/mL) was documented in 29.0% of patients tested in a recent
NIH-PA Author Manuscript
POTS with Deconditioning
POTS patients have poor exercise tolerance, and deconditioning is often present, especially
in patients with prominent fatigue and fibromyalgia type symptoms. In an attempt to
segregate psychologic and exercise contributions, a study was designed to separate the roles
of venous pooling and anxiety. During LBNP, the tachycardia in POTS patients was
markedly blunted during LBNP with mast trouser inflation to 5 mmHg to prevent venous
pooling, and there was no HR increase during vacuum application without LBNP in either
group. HR responses during mental stress were not different in the patients and controls (18
± 2 vs 19 ± 1 bpm; P > 0.6). Anxiety, somatic vigilance, and catastrophic cognitions were
significantly higher in the patients (P < 0.05), but not related to the HR responses during
LBNP or mental stress (P > 0.1). We concluded that although anxiety is commonly present
in POTS, the HR response to orthostatic stress in POTS patients is not caused by anxiety,
but is a physiological response that maintains arterial pressure during venous pooling.
Masuki et al.15 studied 13 patients with mild POTS and 10 matched controls. Exercise was
associated with a greater elevation in HR in POTS patients, especially while upright, was
secondary to reduced stroke volume, and was associated with poor exercise tolerance. It was
NIH-PA Author Manuscript
demonstrated that the tachycardia during exercise was due to a compensatory response to
low stroke volume and not due to altered baroreflex function during exercise.15 Both the
LBNP and exercise findings seem remarkably similar to models of pure deconditioning and
bed rest. These findings in combination with the “somatic hypervigilance” noted above raise
the possibility that in at least some POTS patients there was an initial event or illness that
evoked orthostatic symptoms and that the symptoms were then “over-interpreted” and
followed by reduced physical activity and deconditioning. In the context, the residual
symptoms in POTS may have a strong deconditioning component in at least some patients.
It is important to adopt a systematic, mechanism-based and practical approach.1,3,4,10,11,25
Step 1: Based on a detailed history, examination, and a general medical evaluation including
EKG, it should be possible to decide if further evaluation is warranted. The degree of
orthostatic intolerance should be graded (Table 2). The patient with POTS (standing HR
>120 bpm, consistent orthostatic symptoms, significant impairment in ability to perform
activities of daily living), that is, grades 3 or 4 by symptoms, should be further evaluated and
treated. Many of the patients with mild orthostatic intolerance have a recognizable
NIH-PA Author Manuscript
mechanism, and may not need detailed evaluation. Such a patient might be an individual
with constitutional orthostatic intolerance, or deconditioning (patients confined to bed for
more than a few days; debilitating illness), or hypovolemia.
Step 2: Once a decision to evaluate the patient is made, the study should comprise a
cardiologic and autonomic laboratory evaluation. The cardiologic evaluation will usually
comprise a cardiologic interview and examination, EKG, chest X-ray, and a 24-hour Holter
monitor. A 24-hour Holter monitoring is useful to determine the mean heart rate, heart rate
fluctuation according to activities, limited P-wave morphology from 3-standard leads, and
correlation of symptoms to rate and rhythm. Additional heart rate assessment could be
considered on an elective basis, including an ambulatory event loop recorder to correlation
heart rate to symptoms and treadmill exercise test to assess heart rate response to activity.
A diagnostic electrophysiologic study is usually not indicated unless the etiology or
mechanism of the documented tachycardia is uncertain or when other supraventricular
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 6
tachyarrhythmias are suspected.26,27 During the study, programmed stimulation is
performed to exclude sinus node reentry tachycardia, atrioventricular nodal reentrant
NIH-PA Author Manuscript
tachycardia, atrioventricular reentrant tachycardia, ectopic atrial tachycardia, and atrial
flutter or atrial fibrillation. Electrocardiographic and electrophysiological features for
atrioventricular nodal tachycardia, atrioventricular tachycardia, atrial flutter and atrial
fibrillation, distinguishable quite readily from sinus tachycardia, will not be discussed here.
Differentiation of sinus tachycardia, sinus node reentrant tachycardia, and ectopic atrial
tachycardia originating near the sinus node can be challenging. Several key features
obtained during electrophysiologic study suggest the diagnosis of tachycardia from the sinus

A gradual increase (warm-up) and decrease (cool-down) in heart rate spontaneously
or during initiation and termination of isoproterenol infusion are consistent with an
automatic mechanism of sinus node function.

The surface P-wave morphology is similar to that observed during sinus rhythm.

During mapping, the earliest endocardial activation is near the area of sinus node
along the crista terminalis estimated from biplane fluoroscopic images, intracardiac
ultrasonography, or advanced 3-D electroanatomic techniques. Atrial
depolarization sequence is usually cranial-caudal along the crista terminalis. During
rate changes, the site of earliest activation shifts up to the crista terminalis at a
NIH-PA Author Manuscript
faster rate and down from the crista terminalis at a slower rate.
Step 3: The neurologic evaluation comprises a neurologic history, examination, and tests21
seeking evidence for an autonomic neuropathy. The autonomic laboratory evaluation
follows and comprises a modified autonomic reflex screen and thermoregulatory sweat test,
plasma catecholamines, and a 24-hour urinary sodium estimation (Table 3).
The cardiologic and autonomic evaluations are synthesized and treatment is planned. POTS
is best considered a syndrome of orthostatic intolerance rather than a disease sui generis. It
is reasonable to document the presence and severity of POTS, seek evidence of associated
autonomic neuropathy, deconditioning or history of vasovagal syndrome. All patients are
required to be educated on the pathophysiology of POTS, aggravating and ameliorating
factors, so as to better handle the condition. All patients need to learn to maintain a high salt
and high fluid intake. Some fine-tuning is helpful depending on pathophysiology. They need
to recognize orthostatic stresses and how to avoid or minimize them. They need to be
educated on measures that improve orthostatic tolerance. Three measures are often
beneficial. The first is physical countermaneuvers. Patients are taught to contract muscles
below the waist, typically for about 30 seconds, and the measure could be repeated.28,29
NIH-PA Author Manuscript
This method reduces venous capacity and increases total peripheral resistance. A second
approach is to wear an abdominal binder. This reduces splanchnic-mesenteric venous
capacity and is especially helpful in patients with poor venomotor tone or are
hypovolemic.30,31 The third maneuver is water bolus therapy. The subject drinks two 8-
ounce glasses of water sequentially. This results in a sympathetically-mediated pressor
response that is sustained for 1–2 hours.32–35 Certain categories of POTS might additionally
benefit from modifications of therapy based on pathophysiology (Table 5). There is
significant overlap in management tools, and Table 5 is provided merely as a guide to
emphasize main mechanisms and major emphases of management.
The Hypovolemic Patient
The hypovolemic patient will do well with expanding plasma volume with generous salt
intake and fludrocortisone. The salt intake should be between 150–250 mEq of sodium (10–
20 g of salt). Some patients are intensely sensitive to salt intake and can fine-tune their
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 7
plasma volume and BP control with salt intake alone. Foods with a high salt content include
fast foods like hamburgers, hotdogs, chicken pieces, fries, and fish fries. Canned soups,
NIH-PA Author Manuscript
chili, ham, bacon, sausage, additives like soya sauce, and commercially processed canned
products also have a high sodium content. The patient should have at least 1 glass or cup of
fluids with their meals and at least 2 at other times each day to obtain 2–2.5 L/day.
Fludrocortisone, with doses up to 0.4 mg in young subjects, can be used initially, with the
dose adjusted downwards to a maintenance dose of 0.1 to 0.2 mg/day.
Neuropathic POTS
The patient with peripheral adrenergic failure, manifested as a loss of late phase II or
occasional or delayed OH, is best treated with fludrocortisone and an α-agonist. Midodrine
appears to work best in terms of absorption, predictable duration of action, and lack of CNS
side effects. The dose of midodrine is usually 5 mg 3 times a day. Some patients do better
when midodrine is combined with pyridostigmine at the dose of 60 mg 3 times a day.
Alternative agents such as ephedrine, phenylpropanolamine, and methylphenidate are
largely of historical interest.
Hyperadrenergic POTS
These patients respond to orthostatic and other stresses with an exaggerated pressor and
NIH-PA Author Manuscript
sometimes tachycardic response. It is important to minimize the orthostatic reduction in
venous return and pulse pressure. To this end, volume expansion and wearing an abdominal
binder are helpful. The latter reduces venous capacitance. Some patients are also helped by
physical countermaneuvers, where the subject contracts dependent muscles. Some patients
seem to be helped by propranolol (e.g., Inderal), a non-β-selective lipophilic agent at a dose
of 10 mg/ day. Presumably, a significant part of its benefit is because of a central effect
since it seems to work better than the β-selective lipophilic agent such as atenolol. A
paticularly difficult subset of patients has unstable hypertensive responses to tilt. Some of
these patients have BP responses up to 250/150 mmHg on standing. Some of these patients
with autonomic instability respond to oral phenobarbital beginning with 60 mg at night and
15 mg q AM. An alternative treatment is clonidine or another α2 agonist. Clonidine is
administered in a dose of 0.1 mg bid and increasing to the maximally tolerated doses.
Reports of response to microvascular decompression of the brain-stem have been reported,
but its role is as yet undefined.
Deconditioned POTS
The concept that at least some of the chronic symptoms in POTS are due in part to
secondary deconditioning raises the possibility that a “life-hardening” exercise training
NIH-PA Author Manuscript
program might have utility in this condition. This approach has been used in a number of
studies of fibromyalgia patients and been successful in reducing disability, and clearly
warrants serious consideration in POTS.36 A recent well-done study in POTS supports this
approach.37 An exercise program, provided it is sustained and adequate for several months,
can be very helpful.37 Based on the small study noted above, the physiological data, and
anecdotal reports, larger clinical trial of exercise training in POTS may be warranted.
POTS is common and is heterogeneous in presentation and pathophysiologic mechanisms.
Common mechanisms are denervation (neuropathic POTS), hyperadrenergic state, and
deconditioning. Management always involves expansion of plasma volume with high salt
and high fluid intake. Additional steps include compression garments. Medications that are
commonly used include beta blockers, midodrine, and fludrocortisones. Exercise training
and reconditioning is emerging as a very important strategy in the deconditioned subject.
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 8
Dr. Low is supported by research grants NS44233 and NS32352.
NIH-PA Author Manuscript
1. Low PA, Opfer-Gehrking TL, Textor SC, Benarroch EE, Shen WK, Schondorf R, Suarez GA,
Rummans TA. Postural tachycardia syndrome (POTS). Neurology. 1995; 45:S19–S25. [PubMed:
2. Streeten DH, Anderson GH Jr, Richardson R, Thomas FD. Abnormal orthostatic changes in blood
pressure and heart rate in subjects with intact sympathetic nervous function: Evidence for excessive
venous pooling. J Lab Clin Med. 1988; 111:326–335. [PubMed: 3343547]
3. Fouad FM, Tadena Thome L, Bravo EL, Tarazi RC. Idiopathic hypovolemia. Ann Intern Med.
1986; 104:298–303. [PubMed: 3511818]
4. Hoeldtke RD, Dworkin GE, Gaspar SR, Israel BC. Sympathotonic orthostatic hypotension: A report
of four cases. Neurology. 1989; 39:34–40. [PubMed: 2909911]
5. Coghlan HC, Phares P, Cowley M, Copley D, James TN. Dysautonomia in mitral valve prolapse.
Am J Med. 1979; 67:236–244. [PubMed: 463929]
6. Bou-Holaigah I, Rowe PC, Kan J, Calkins H. The relationship between neurally mediated
hypotension and the chronic fatigue syndrome. JAMA. 1995; 274:961–967. [PubMed: 7674527]
7. Streeten, DHP. Orthostatic Disorders of the Circulation, Mechanisms, Manifestations and
NIH-PA Author Manuscript
Treatment. New York: Plenum Press; 1987.
8. Schondorf R, Benoit J, Wein T, Phaneuf D. Orthostatic intolerance in the chronic fatigue syndrome.
J Auton Nerv Syst. 1999; 75:192–201. [PubMed: 10189122]
9. Schondorf R, Low PA. Idiopathic postural tachycardia syndrome. Ann Neurol. 1990; 28:271.
10. Low, PA. POTS. In: Low, PA.; Benarroch, EE., editors. Clinical Autonomic Disorders. 3rd ed..
Philadelphia: PA: Lippincott; 2008. p. 515-533.
11. Thieben M, Sandroni P, Sletten D, Benrud-Larson L, Fealey R, Vernino S, Lennon V, Shen W,
Low PA. Postural orthostatic tachycardia syndrome – Mayo Clinic experience. Mayo Clin Proc.
2007; 82:308–313. [PubMed: 17352367]
12. Low PA, Opfer-Gehrking TL, Textor SC, Schondorf R, Suarez GA, Fealey RD, Camilleri M.
Comparison of the postural tachycardia syndrome (POTS) with orthostatic hypotension due to
autonomic failure. J Auton Nerv Syst. 1994; 50:181–188. [PubMed: 7884158]
13. Schondorf R, Low PA. Idiopathic postural orthostatic tachycardia syndrome: An attenuated form
of acute pandysautonomia? Neurology. 1993; 43:132–137. [PubMed: 8423877]
14. Garland EM, Raj SR, Black BK, Harris PA, Robertson D. The hemodynamic and neurohumoral
phenotype of postural tachycardia syndrome. Neurology. 2007; 69:790–798. [PubMed: 17709712]
15. Masuki S, Eisenach JH, Johnson CP, Dietz NM, Benrud-Larson LM, Schrage WG, Curry TB,
Sandroni P, Low PA, Joyner MJ. Excessive heart rate response to orthostatic stress in postural
NIH-PA Author Manuscript
tachycardia syndrome is not caused by anxiety. J Appl Physiol. 2007; 102:896–903. [PubMed:
16. Gibbons CH, Freeman R. Delayed orthostatic hypotension: A frequent cause of orthostatic
intolerance. Neurology. 2006; 67:28–32. [PubMed: 16832073]
17. El-Sayed H, Hainsworth R. Salt supplementation increases plasma volume and orthostatic
tolerance in patients with unexplained syncope. Heart. 1996; 75:134–140. [PubMed: 8673750]
18. Huang CC, Sandroni P, Sletten D, Weigand S, Low PA. Effect of age on adrenergic and vagal
baroreflex sensitivity in normal subjects. Muscle Nerve. 2007; 36:637–642. [PubMed: 17654557]
19. Schrezenmaier C, Singer W, Muenter Swift N, Sletten D, Tanabe J, Low PA. Adrenergic and vagal
baroreflex sensitivity in autonomic failure. Arch Neurol. 2007; 64:381–386. [PubMed: 17353381]
20. Vogel ER, Sandroni P, Low PA. Blood pressure recovery from Valsalva maneuver in patients with
autonomic failure. Neurology. 2005; 65:1533–1537. [PubMed: 16301478]
21. Low PA. Autonomic nervous system function. J Clin Neurophysiol. 1993; 10:14–27. [PubMed:
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 9
22. Fealey RD, Low PA, Thomas JE. Thermoregulatory sweating abnormalities in diabetes mellitus.
Mayo Clin Proc. 1989; 64:617–628. [PubMed: 2747292]
NIH-PA Author Manuscript
23. Jacob G, Costa F, Shannon JR, Robertson RM, Wathen M, Stein M, Biaggioni I, Ertl A, Black B,
Robertson D. The neuropathic postural tachycardia syndrome. N Engl J Med. 2000; 343:1008–
1014. [PubMed: 11018167]
24. Jordan J, Shannon JR, Diedrich A, Black BK, Robertson D. Increased sympathetic activation in
idiopathic orthostatic intolerance: Role of systemic adrenoreceptor sensitivity. Hypertension.
2002; 39:173–178. [PubMed: 11799098]
25. Grubb BP, Kanjwal Y, Kosinski DJ. The postural tachycardia syndrome: A concise guide to
diagnosis and management. J Cardiovasc Electrophysiol. 2006; 17:108–112. [PubMed: 16426415]
26. Brady PA, Low PA, Shen WK. Inappropriate sinus tachycardia, postural orthostatic tachycardia
syndrome, and overlapping syndromes. Pacing Clin Electrophysiol. 2005; 28:1112–1121.
[PubMed: 16221272]
27. Shen WK. How to manage patients with inappropriate sinus tachycardia. Heart Rhythm. 2005;
2:1015–1019. [PubMed: 16171763]
28. Bouvette CM, McPhee BR, Opfer-Gehrking TL, Low PA. Role of physical countermaneuvers in
the management of orthostatic hypotension: Efficacy and biofeedback augmentation. Mayo Clin
Proc. 1996; 71:847–853. [PubMed: 8790259]
29. van Lieshout JJ, ten Harkel AD, Wieling W. Physical manoeuvres for combating orthostatic
dizziness in autonomic failure. Lancet. 1992; 339:897–898. [PubMed: 1348300]
30. Denq JC, Opfer-Gehrking TL, Giuliani M, Felten J, Convertino VA, Low PA. Efficacy of
NIH-PA Author Manuscript
compression of different capacitance beds in the amelioration of orthostatic hypotension. Clin
Auton Res. 1997; 7:321–326. [PubMed: 9430805]
31. Tani H, Singer W, McPhee BR, Opfer-Gehrking TL, Low PA. Splanchnic and systemic circulation
in the postural tachycardia syndrome. Clin Auton Res. 1999; 9:231–232.
32. Jordan J, Shannon JR, Grogan E, Biaggioni I, Robertson D. A potent pressor response elicited by
drinking water. Lancet. 1999; 353:723. [PubMed: 10073520]
33. Jordan J, Shannon JR, Black BK, Ali Y, Farley M, Costa F, Diedrich A, Robertson RM, Biaggioni
I, Robertson D. The pressor response towater drinking in humans: A sympathetic reflex?
Circulation. 2000; 101:504–509. [PubMed: 10662747]
34. Schroeder C, Bush VE, Norcliffe LJ, Luft FC, Tank J, Jordan J, Hainsworth R. Water drinking
acutely improves orthostatic tolerance in healthy subjects. Circulation. 2002; 106:2806–2811.
[PubMed: 12451007]
35. Shannon JR, Diedrich A, Biaggioni I, Tank J, Robertson RM, Robertson D, Jordan J. Water
drinking as a treatment for orthostatic syndromes. Am J Med. 2002; 112:355–360. [PubMed:
36. Gowans SE, Dehueck A, Voss S, Silaj A, Abbey SE. Six-month and one-year followup of 23
weeks of aerobic exercise for individuals with fibromyalgia. Arthritis Rheum. 2004; 51:890–898.
[PubMed: 15593364]
NIH-PA Author Manuscript
37. Winker R, Barth A, Bidmon D, Ponocny I, Weber M, Mayr O, Robertson D, Diedrich A, Maier R,
Pilger A, Haber P, Rudiger HW. Endurance exercise training in orthostatic intolerance: A
randomized, controlled trial. Hypertension. 2005; 45:391–398. [PubMed: 15699447]
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 10
NIH-PA Author Manuscript
NIH-PA Author Manuscript
NIH-PA Author Manuscript
Figure 1.
Examples of blood pressure (BP) and heart rate recordings from a normal subject (top
panel), a patient with neuropathic POTS (middle panel), and a patient with hyperadrenergic
POTS (bottom panel). Note the modest reduction in BP in neuropathic POTS.
Hyperadrenergic POTS is associated with prominent BP oscillations, an orthostatic
increment in systolic BP, and a prominent norepinephrine response to head-up tilt.
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 11
NIH-PA Author Manuscript
Orthostatic Symptoms as Frequency (%) in Patients with POTS
Orthostatic symptoms
  Light headed or dizziness
  Exacerbation by heat
  Exacerbation by exercise
  Sense of weakness
  Shortness of breath
  Chest pain
  Exacerbation by meals
  Exacerbation associated with menses
NIH-PA Author Manuscript
  Loss of sweating
Nonorthostatic symptoms
  Abdominal pain
  Bladder symptoms
  Pupillary symptoms (glare)
Diffuse associated symptoms
  Sleep disturbance
  Migraine headache
  Myofascial pain
NIH-PA Author Manuscript
  Neuropathic type pain
(From Thieben MJ, Sandroni P, Sletten DM, Benrud-Larson LM, Fealey RD, Vernino S, Lennon VA, Shen WK, Low PA. Postural Orthostatic
Tachycardia Syndrome: The Mayo Clinic Experience. Mayo Clinic Proceedings 82:308–313, 2007. Modified with permission.)
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 12
NIH-PA Author Manuscript
The Grading of Orthostatic Intolerance
  Normal orthostatic tolerance
Grade I
Orthostatic symptoms are infrequent, or only under conditions of increased orthostatic stress**
Able to stand >15 minutes on most occasions
The subject typically has unrestricted activities of daily living
Grade II
Orthostatic symptoms are frequent, developing at least once a week Orthostatic symptoms commonly develop with orthostatic stress
Able to stand >5 minutes on most occasions
Some limitation in activities of daily living is typical
Grade III
Orthostatic symptoms develop on most occasions, and are regularly unmasked by orthostatic stresses
NIH-PA Author Manuscript
Able to stand >1 minute on most occasions
Marked limitation in activities of daily living
Grade IV
Orthostatic symptoms are consistently present
Able to standing <1 minute on most occasions
Patient is seriously incapacitated, being bed- or wheel chair bound because of orthostatic intolerance
  Syncope/presyncope is common if patient attempts to stand
Symptoms may vary with time and state of hydration and circumstances.
**Orthostatic stresses include prolonged standing, a meal, exertion, or heat stress.
NIH-PA Author Manuscript
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 13
NIH-PA Author Manuscript
Evaluation of Suspected POTS
Routine Evaluation of POTS
Plasma catecholamines, supine, and standing
24-hour urinary sodium
Additional Tests
Autonomic reflex screen
Thermoregulatory sweat test
Ganglionic antibody
Exercise testing
Cardiac echo and Holter monitor
NIH-PA Author Manuscript
NIH-PA Author Manuscript
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 14
NIH-PA Author Manuscript
NIH-PA Author Manuscript
Ganglionic Antibody
Sometimes positive in low titers
Distal anhidrosis

N or 
Plasma NE
>600 pg/mL
NIH-PA Author Manuscript


Some Distinguishing Features of Common Types of POTS
POTS Category
HUT = head-up tilt; PP = pulse pressure; QSART = quantitative sudomotor axon-reflex test; TST = thermoregulatory sweat test.
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.

Low et al.
Page 15
NIH-PA Author Manuscript
NIH-PA Author Manuscript
Usual Main Approach
Low-dose midodrine, with some volume expansion and compression
Volume expansion and reduce sympathetic action (central/peripheral)
Sustained exercise program in deconditioned patient; volume expand
PCM and
NIH-PA Author Manuscript
Approach to Treatment of Common Types of POTS
POTS Category
Deconditioned/ hypovolemic
+, ++, +++: slightly, moderately, very important.
J Cardiovasc Electrophysiol. Author manuscript; available in PMC 2014 January 28.