Postural orthostatic tachycardia syndrome
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. Several studies show a decrease in cerebral blood flow with systolic and diastolic CBF velocity decreased 44 and 60%, respectively 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.
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.
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.
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, 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.
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.
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.