Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by too little blood returning to the heart when moving from a lying down to a standing up position (orthostatic intolerance). POTS causes lightheadedness or fainting that can be eased by lying back down. Although POTS can affect men and women of all ages, most cases are diagnosed in women between the ages of 15 and 50. In women, episodes may also begin after pregnancy and the symptoms may worsen or the number of episodes may increase right before menstruation. The goal of treatment is to increase blood flow, lower heart rate, sometimes increase blood pressure, and improve circulatory problems that may be causing POTS.

Postural orthostatic tachycardia syndrome may also be referred to as POTS, postural tachycardia syndrome, or chronic orthostatic intolerance.

The cause of postural orthostatic tachycardia syndrome is poorly understood. However, episodes often begin after major surgery, trauma, or a viral illness. It can also be caused by chronic conditions such as diabetes or sarcoidosis, as well as connective tissue disorders like Ehlers-Danlos syndrome and scleroderma. Many researchers suspect that the condition may have more than one cause. The following abnormalities can be associated with POTS and may play a role in it's development: Impaired function of nerves in certain muscles, especially those in the legs and feet. An abnormal decrease in the amount of blood circulating in the body (caused, for example, by blood pooling in the abdomen and legs). Too little blood returning to the heart when moving from a lying down to a standing up position. Changes in heart and blood vessel function. Abnormal regulation of blood pressure. Increased fight-or-flight response. Although most cases of POTS occur in people with no history of the condition in their family, some affected people report a family history of orthostatic intolerance. This suggests that in some cases, genetic factors may play a role in the development of POTS. Some studies also suggest that normal variations (polymorphisms) in certain genes (NOS3, ADRB2) may be associated with an increased risk of developing the condition. A mutation in the norepinephrine transporter gene (SLC6A2) has been found in one family with POTS.

Postural orthostatic tachycardia syndrome is characterized by orthostatic intolerance and a rapid increase in heart rate. People with POTS often have hypovolemia (low blood volume) and high levels of plasma norepinephrine while standing, reflecting increased sympathetic nervous system activation. Approximately half of affected people have a small fiber neuropathy that impacts their sudomotor nerves (those that activate the sweat glands). Some individuals develop a reddish-purple color in the legs when they stand, thought to be due to blood pooling or poor circulation. The color change subsides upon returning to a reclined position. Other symptoms that have been reported in people with POTS include: Blurred vision Lightheadedness, dizziness or fainting Heart palpitations Headache Poor concentration Fatigue Gastrointestinal symptoms (for example, nausea, cramps, bloating, constipation, diarrhea) Shortness of breath Head, neck or chest discomfort Weakness Insomnia Tremors Nausea Brain Fog Abdominal Pain Fatigue Difficulty exercising Anxiety Coldness, pain, or discoloration of the extremities While the underlying causes of POTS are still being studied, a number of underlying conditions have been associated with POTS or with symptoms seen in POTS.

A diagnosis of postural orthostatic tachycardia syndrome is often suspected based on characteristic signs and symptoms. Additional testing can then be ordered to confirm the diagnosis. Many physicians will conduct a physical examination that includes measurement of blood pressure and heart rate while lying, sitting, and standing. A tilt table test, in which blood pressure and heart rate are checked while a person is safely moved from a lying down position to standing upright, may also be recommended. Because research suggests that postural orthostatic tachycardia syndrome (POTS) has a variety of causes, no single treatment is effective for all affected people. Management of POTS aims to improve low blood pressure and problems with the heart and blood vessels that may be causing the condition. In some people with POTS, simple lifestyle changes such as adding extra salt to the diet, drinking more fluids, exercising, and avoiding factors that make the condition worse, may lessen symptoms. Certain medications may also be helpful in treating POTS. Some researches suggest volume repletion and fludrocortisone (0.05 to 0.2 mg per day) as the first line of therapy. Some patients may benefit from midodrine or beta blocking agents. Other treatment options remain under investigation, and further confirmation of benefit is needed before they can be recommended.

The long-term outlook (prognosis) for people with postural orthostatic tachycardia syndrome is generally good, but may be poor in some cases. While many people have fairly mild symptoms and can continue with regular daily activities, others may be severely affected with limited abilities. Some people with POTS report significantly improved symptoms within a year, while others don't improve with treatment and may worsen over time. With proper lifestyle changes (for example, exercise and diet) and medical treatments, many affected people see an improvement in symptoms and quality of life. In some cases, people with POTS may even become symptom-free over time.