Postural orthostatic tachycardia syndrome

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Postural orthostatic tachycardia syndrome (often referred to as just postural tachycardia syndrome or POTS) is a condition of dysautonomia, and more specifically, orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia. This is often, but not always, accompanied by a fall in blood pressure. Patients with POTS have problems maintaining homeostasis when changing position, i.e. moving from one chair to another or reaching above their heads. Many patients also experience symptoms when stationary or even while lying down. Symptoms present in various degrees of severity depending on the patient. POTS is a serious, though non-life threatening, medical condition that can be severely disabling and debilitating. Many patients are unable to attend school or work, and especially severe cases can completely incapacitate the patient.

History
POTS was first named and identified by Schondorf and Low in 1993, however the syndrome has been described in medical studies dating back to at least 1940. Hypertension associated with POTS has been previously described as the "hyperadrenergic syndrome" by Streeten and "idiopathic hypovolemia" by Fouad. Hypotension associated with POTS has been previously described as the "neurally mediated hypotension" form of POTS

Symptoms
The hallmark symptom of POTS is an increase in heart rate from the supine to upright position of more than 30 beats per minute or to a heart rate greater than 120 beats per minute within 10 minutes of head-up tilt. This tachycardic response is often accompanied by a profound decrease in blood pressure and a wide variety of symptoms associated with hypotension including:


 * lightheadedness, sometimes called pre-syncope (pre-fainting) dizziness (but not vertigo, which is also called dizziness)
 * exercise intolerance
 * extreme fatigue
 * syncope (fainting)

Chronic or acute hypoperfusion of tissues and organs in the upper parts of the body are thought to cause the following symptoms:


 * cold extremities
 * chest pain and discomfort
 * disorientation
 * dyspnea
 * headache
 * muscle weakness
 * tremulousness
 * visual disturbances

Autonomic dysfunction is thought to cause additional gastrointestinal symptoms:
 * abdominal pain or discomfort
 * bloating
 * constipation
 * diarrhea
 * nausea
 * vomiting

Cerebral hypoperfusion can cause cognitive and emotive difficulties:
 * brain fog
 * burnout
 * decreased mental stamina
 * depression
 * difficulty finding the right word
 * impaired concentration
 * sleep disorders

Inappropriate levels of epinephrine and norepinephrine lead to anxiety-like symptoms:
 * chills
 * feelings of fear
 * flushing
 * overheating
 * nervousness
 * over-stimulation

Symptoms of POTS overlap considerably with those of generalized anxiety disorder, and a misdiagnosis of an anxiety disorder is not uncommon.

Associated Conditions

 * POTS is often accompanied by vasovagal syncope, also called "neurally mediated hypotension" (NMH) or "neurocardiogenic syncope" (NCS). Vasovagal syncope is a fainting reflex due to a profound drop in blood pressure. Autonomic disfunction that occurs with these disorders causes blood to inappropriately pool in the limbs away from the heart, lungs, and brain. The combination of misdirected bloodflow and hypotension will invoke syncope. Tachycardia associated with POTS may be a cardiac response to restore cerebral hypoperfusion.
 * POTS may be a cause of chronic fatigue syndrome in patients that exhibit signs of orthostatic intolerance. Treating POTS will greatly improve or even eliminate disabling fatigue for these patients.
 * Some patients with fibromyalgia complain of dysautonomia-related symptoms. Treating these patients for POTS will often improve myofascial and neuropathic pain.
 * Autonomic dysfunction is most likely responsible for irritable bowel syndrome in many patients as well.
 * Patients with Ehlers-Danlos Syndrome (EDS) often develop POTS as a secondary condition.
 * Some POTS patients experience symptoms associated with Restless Leg Syndrome, or RLS. Treating POTS should also relieve RLS symptoms in these patients.

Causes
The causes of POTS are not fully known. Most patients develop symptoms in their teenage years during a period of rapid growth and see gradual improvement into their mid-twenties. Others develop POTS after a viral or bacterial infection such as mononucleosis or pneumonia. Some patients develop symptoms after experiencing some sort of trauma such as a car accident or injury. Women can also develop POTS during or after pregnancy. These patients generally have a poorer prognosis. In one large test, 12.5% of 152 patients with POTS reported a family history of orthostatic intolerance, suggesting that there is a genetic inheritance associated with POTS.

Diagnosis
POTS can be difficult to diagnose. A routine physical examination and standard blood tests will not indicate POTS. A tilt table test is vital to diagnosing POTS, although all symptoms must be considered before a final diagnosis is made. Tests to rule out Addison's Disease, pheochromocytoma, electrolyte imbalance, Lyme Disease, Celiac Disease, Ehlers-Danlos Syndrome, and various food allergies are usually performed. A blood test may be performed to verify abnormally high levels of norepinephrine present in some POTS patients.

Between 75 and 80 percent of POTS patients are female and of the menstruating age. Most male patients develop POTS in their early to mid-teens during a growth spurt or following a viral or bacterial infection. Some women also develop POTS symptoms during or after pregnancy.

Prognosis
Most POTS patients will see symptom improvement over the course of several years. Those who develop POTS in their early to mid teens during a period of rapid growth will most likely see complete symptom resolution by their mid twenties. Patients with post-viral POTS will also usually improve greatly or see a full symptom resolution. Adults who develop POTS, especially women during or after pregnancy, usually see milder improvement and can be plagued with their condition for life. Rarely, a teenager who develops POTS will gradually worsen overtime and have lifelong symptoms. Patients with secondary POTS as a consequence of Ehlers-Danlos Syndrome will also usually struggle with symptoms for life.

Recovered individuals do complain of occasional, non-debilitating recurrence of symptoms associated with autonomic dysfunction including dizzy spells, lightheadedness, flushing, transient syncope, and symptoms of irritable bowel syndrome.

Treatment
There is at this time only one drug approved by the FDA to treat orthostatic intolerance, however several classes of drugs often provide symptom control and relief. Treatments must be carefully tested due to medication sensitivity often associated with POTS patients, and each patient will respond to different therapies in different ways. Most patients will respond to some form of treatment.

Fludrocortisone
The first line of treatment for POTS is usually fludrocortisone, or Florinef, a corticosteroid used to increase sodium retention and thus increase blood volume and blood pressure. An increase in sodium and water intake must coincide with fludrocortisone therapy for effective treatment. Dietary increases in sodium and sodium supplements are often used. Gatorade is also effective in providing both sodium and fluid.

Beta Blockers
Beta blockers such as atenolol and propanolol are often prescribed to treat POTS. These medications work by blocking the effects of epinephrine and norepinephrine released by the autonomic nervous system. Beta blockers also reduce sympathetic activity by blocking sympathetic impulses.

Midodrine
Midodrine (Proamatine), is approved by the U.S. FDA to treat orthostatic hypotension, a condition related to POTS. It is a stimulant that causes vasoconstriction and thereby increases blood pressure and allows more blood to return to the upper parts of the body. Use of midodrine is often discontinued due to intolerable side-effects, and it is known to cause supine hypertension (high blood pressure when lying down).

Antidepressants
Antidepressants, especially selective serotonin reuptake inhibitors (SSRIs) such as Prozac, Zoloft, Celexa, Lexapro, and Paxil, can be extremely effective in re-regulating the autonomic nervous system and raising blood pressure. Some studies indicate that serotonin-norepinephrine reuptake inhibitors (SNRIs) such as Effexor and Cymbalta are even more effective. Tricyclic antidepressants, tetracyclic antidepressants, and monoamine oxidase inhibitors are also occasionally, but rarely, prescribed. A combination of two antidepressants, usually an SSRI or SNRI with Wellbutrin or Remeron, is also shown to be very effective.

Stimulants
Medications used to treat ADD and ADHD such as Ritalin and Adderall are used to balance dopamine levels, increase vasoconstriction, and increase blood pressure.

Anxiolytics
Anti-anxiety medications, such as Xanax, Ativan, and Klonopin, can be used to combat imbalances of adrenaline usually seen with POTS patients.

Other Medications

 * Angiotensin converting enzyme inhibitors, or ACE inhibitors, are used to increase vasoconstriction, cardiac output, and sodium and water retention.
 * Clonidine can work in patients with reduced sympathetic activity. Ironically an anti-hypertensive drug, Clonidine promotes production and release of epinephrine and norepinephrine.
 * Disopyramide, or Norpace, is an antiarrhythmic medication that inhibits the release of epinephrine and norepinephrine.
 * Erythropoietin, used to treat anemia via intravenous infusion, is very effective at increasing blood volume. It is seldom used, however, due to the dangers of increasing the hematocrit, the inconvenience of intravenous infusion, and its prohibitively expensive cost.
 * Pregabalin, or Lyrica, an anticonvulsant drug, has been shown to be especially effective in treating neuropathic pain associated with POTS. In fact, Lyrica is currently the only prescription drug approved by the FDA to treat fibromyalgia. Some POTS patients also report improvement in concentration and energy while on Lyrica.
 * Pseudoephedrine and phenylephrine, over the counter decongestants, increase vasoconstriction by promoting the release of norepinephrine.
 * Pyridostigmine, or Mestinon, inhibits the breakdown of acetylcholine, promoting autonomic nervous system activity. It is especially effective in patients who exhibit symptoms of excessive sympathetic activity.
 * Theophylline, a drug used to treat respiratory diseases such as COPD and asthma, is occasionally prescribed at low doses for POTS patients. Theophylline increases cardiac output, increases blood pressure, and stimulates epinephrine and norepinephrine production. Due to its very narrow therapeutic index, Theophylline is known to cause a wide variety of side-effects and even toxicity.
 * Women who report a worsening of symptoms during menstruation will often use combined (containing both estrogen and progestin) forms of hormonal contraception to prevent hormonal changes and an aggravation of their condition.

Dietary Changes

 * Alcohol has been shown to drastically exacerbate all types of orthostatic intolerance due to its vasodilation and dehydration properties. It should be avoided whenever possible because of its adverse effects and its interactivity with many of the medications prescribed to POTS patients.
 * Caffeine helps some POTS patients due to its stimulative effects, however, other patients report a worsening of symptoms with caffeine intake. Each patient should experiment to determine whether caffeine helps or hurts his or her condition.
 * Diets high in carbohydrates have been connected to impaired vasoconstrictive action. Eating foods with lower carbohydrate levels can mildly improve POTS symptoms.
 * Eating frequent, small meals can reduce gastrointestinal symptoms associated with POTS by requiring the diversion of less blood to the abdomen.
 * Patients diagnosed with POTS will usually be advised to maintain a high sodium diet in order to augment the effects of their medication regimen, especially if that regimen includes fludrocortisone. Patients should also drink plenty of fluids, with a recommended intake of at least two liters per day and as much as 500 milliliters every two hours throughout the day.

Physical Therapy
POTS symptoms can be worsened by postural asymmetries, restrictions in mobility, and areas of adverse mechanical tension in the nervous system. These physical abnormalities can be relieved with gentle manual therapies including neural mobilization (or neural tension work), myofascial release, and cranio-sacral therapy.

External Body Pressure
Pressure garments can reduce symptoms associated with orthostatic intolerance by constricting blood pressures with external body pressure. Compression hose and anti-embolism stockings, both knee and thigh-high, provide relief for many patients. For especially severe cases, military anti-shock trousers and anti-gravity suits, or g-suits can be helpful but also limiting.

Exercise
Exercise is very important for maintaining muscle strength and avoiding deconditioning. Though many POTS patients report difficulty exercising, some form of exercise is essential to controlling symptoms and eventually, improving the condition.