Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) is a condition in which a change from lying to standing causes an abnormally large increase in heart rate. This occurs with symptoms that may include lightheadedness, trouble thinking, blurred vision or weakness. Other commonly associated conditions include irritable bowel syndrome, insomnia, chronic headaches, Ehlers–Danlos syndrome, chronic fatigue syndrome and fibromyalgia. Postural orthostatic tachycardia syndrome (POTS) is a condition in which a change from lying to standing causes an abnormally large increase in heart rate. This occurs with symptoms that may include lightheadedness, trouble thinking, blurred vision or weakness. Other commonly associated conditions include irritable bowel syndrome, insomnia, chronic headaches, Ehlers–Danlos syndrome, chronic fatigue syndrome and fibromyalgia. The causes of POTS are varied. Often, it begins after a viral infection, surgery or pregnancy. Risk factors include a family history of the condition. Diagnosis in adults is based on an increase in heart rate of more than 30 beats per minute within ten minutes of standing up which is accompanied by symptoms. Low blood pressure with standing, however, does not occur. Other conditions which can cause similar symptoms, such as dehydration, heart problems, adrenal insufficiency and Parkinson disease, must not be present. Treatment may include avoiding factors that bring on symptoms, increasing dietary salt and water, compression stockings, exercise, cognitive behavioral therapy (CBT) and medications. Medications used may include beta blockers, pyridostigmine, midodrine or fludrocortisone. More than 50% of people whose condition was triggered by a viral infection get better within five years. About 90% improve with treatment. It is estimated that 0.5 million people are affected in the United States. The average age of onset is 20 years old, and it occurs about 5 times more often in females. In adults the primary symptom is an increase in heart rate of more than 30 beats per minute within ten minutes of standing up. The resulting heart rate is typically more than 120 beats per minute. For people aged between 12 and 19, the minimum increase for diagnosis is 40 beats per minute. This symptom is known as orthostatic (upright) tachycardia (fast heart rate). It occurs without any coinciding drop in blood pressure, as that would indicate orthostatic hypotension. Certain medications to treat POTS may cause orthostatic hypotension. It is accompanied by other features of orthostatic intolerance—symptoms which develop in an upright position and are relieved by reclining. These orthostatic symptoms include palpitations, light-headedness, chest discomfort, shortness of breath, nausea, weakness or 'heaviness' in the lower legs, blurred vision and cognitive difficulties. Symptoms may be exacerbated with prolonged sitting, prolonged standing, alcohol, heat, exercise, or eating a large meal. In up to one third of people with POTS, fainting occurs in response to postural changes or exercise. Migraine-like headaches are common, sometimes with symptoms worsening in an upright position (orthostatic headache). Some people with POTS develop acrocyanosis, or blotchy, red/blue skin upon standing, especially over the feet (indicative of blood pooling). 48% of people with POTS report chronic fatigue and 32% report sleep disturbances. Others exhibit only the cardinal symptom of orthostatic tachycardia. The symptoms of POTS can be caused by several distinct pathophysiological mechanisms. These mechanisms are poorly understood, and can overlap, with many people showing features of multiple POTS types. Many people with POTS exhibit low blood volume (hypovolemia), which can decrease the rate of blood flow to the heart. To compensate for this, the heart increases its cardiac output by beating faster, leading to the symptoms of presyncope and reflex tachycardia. In the 30% to 60% of cases classified as hyperadrenergic POTS, norepinephrine levels are elevated on standing, often due to hypovolemia or partial autonomic neuropathy. A smaller minority of people with POTS have (typically very high) standing norepinephrine levels that are elevated even in the absence of hypovolemia and autonomic neuropathy; this is classified as central hyperadrenergic POTS. The high norepinephrine levels contribute to symptoms of tachycardia. Another subtype, neuropathic POTS, is associated with denervation of sympathetic nerves in the lower limbs. In this subtype, it is thought that impaired constriction of the blood vessels causes blood to pool in the veins of the lower limbs. Heart rate increases to compensate for this blood pooling. In up to 50% of cases, POTS is associated with recent viral illness. It may also be associated with physical deconditioning or chronic fatigue syndrome. During viral illness or prolonged bed rest, the body may become conditioned to orthostatic intolerance and excitability of the central nervous system, resulting in a failure to re-adapt to the normal demands of standing or exercise. POTS is more common in females than males. It has also been shown to be linked in patients with acute stressors such as pregnancy, recent surgery, or recent trauma. POTS has been also linked to patients with a history of autoimmune diseases, irritable bowel syndrome, anemia, hyperthyroidism, fibromyalgia, diabetes, amyloidosis, sarcoidosis, systemic lupus erythematosus, and cancer. Genetics likely plays a role, with one study finding that 1 in 8 POTS patients reported a history of orthostatic intolerance in their family.