The Postural Tachycardia Syndrome, or “POTS,” is a condition that was first described many decades ago, but most people have never heard of it until recently. It still remains relatively misunderstood in most medical practices. Patients with POTS are often misdiagnosed as having “chronic fatigue syndrome,” panic attacks or anxiety, cardiac arrhythmias, or some undescribed malady. POTS is also known as “orthostatic intolerance,” with the word orthostatic referring to the act of standing up. The most common symptoms of POTS include a sense of a rapid heart beat, lightheadedness, fatigue, exercise intolerance, decreased concentration, and rarely fainting, all of which occur mainly when the patient is standing for a period of time. It affects mostly women, and can be seen in people from teenage years up to middle age. Symptoms can be severe enough to interfere with normal everyday activities, and younger patients can be severely debilitated such that they cannot attend school. The most common way of diagnosing POTS in patients with these symptoms is by demonstrating an increase of heart rate of at least 30 beats per minute (or having the heart rate exceed 120 beats per minute) within 10 minutes of standing up. So if your resting pulse runs 70 beats per minute (bpm) lying down but increases to 105 bpm when you stand up, you may have POTS. Generally, the blood pressure stays the same or may even increase slightly, so fainting is not common in patients with this version of dysautonomia.
There are different forms of POTS. The most common variety affects patients fairly suddenly, often after a viral illness. It is known as the “partial dysautonomic” form of POTS. The exact cause is not entirely understood, but there is some evidence that it may be due to an “autoimmune” process, whereby antibodies from the body attack the patient’s own nervous system, specifically affecting the autonomic nervous system that controls the blood vessels. As a result, the blood vessels are unable to respond to the need to constrict, and as a result there seems to be an excessive amount of pooling of blood in the legs when the patient stands up for more than a few minutes. Without an effective means of getting the blood to go uphill from the legs to the heart, the heart cannot pump sufficient blood to meet the body’s needs. The brain responds by increasing the heart rate to compensate for a low blood flow state. However, it’s not enough, so patients feel “run down” and lightheaded, together with a sense of a racing heartbeat. The diagnosis of POTS can be made with formal Tilt Table Testing, but often a history and physical examination (with measurement of blood pressure and heart rate in different positions) can be sufficient.
A second, less common, form of POTS is the “hyperadrenergic” form. That name implies an excessive amount of heart-stimulating hormones like adrenaline. These patients tend to have more complaints of palpitations, tremors, sweating, and headaches, and they can sometimes develop high blood pressure. The onset is often younger, and the symptoms begin gradually, not suddenly like the partial dysautonomic POTS patients. Some recent data suggest that this may be a genetic disorder that results in excessive adrenaline stimulation to the heart. It is usually diagnosed with Tilt Table Testing together with blood levels of these stimulating hormones.
There are certain medical conditions and drugs that can cause the signs and symptoms of POTS. In this case, we refer to it as “secondary POTS.” Diseases that cause secondary POTS include diabetes, sarcoidosis, amyloidosis, Sjogren’s Syndrome (mixed connective tissue disease), and lupus. Sometimes POTS may be an early sign of a more diffuse form of autonomic failure such as pure autonomic failure or multiple systems atrophy, or may be a sign of underlying cancer.
The treatment of POTS should always be individualized, depending on the type of POTS, the age of onset, the severity, and the duration of the symptoms. Drinking plenty of water and eating a high salt diet are the first steps. Certain exercises can be helpful, including aerobic exercise (if they can tolerate it) and leg-strengthening exercises to improve the circulation and enhance the blood return to the heart. There are a variety of medications that can be helpful as well. Luckily, most young patients with the partial dysautonomic type of POTS recover on their own after a few years.