Any time the brain is getting too little blood flow, the usual result is a lightheaded or spacey feeling. Some people describe this as a “head rush.” Recurrent lightheadedness is a common symptom of Postural Tachycardia Syndrome , or POTS. If lightheadedness is severe, individuals may have dimming of their vision, may hear sounds as though they were far away, and may have nausea or vomiting. They may faint because not enough blood is getting to the brain. Fainting is helpful, in that it restores a person to the flat position, removing the effect of gravity on blood pooling in the limbs, and allowing more blood to return to the heart.
Following the episodes of lightheadedness or fainting, most people feel tired for several hours (sometimes more than a day) and their thinking can be somewhat foggy. Some patients with POTS experience prolonged fatigue after a modest amount of physical activity, or after sustaining quiet activity like sitting at a desk. This fatigue after exertion or sustained activity can also last 24-72 hours, and can interfere with many daily activities.
In people with POTS, a fast heart rate is a defining feature, and awareness of vigorous or skipped heart beats (palpitations) is common. In addition, patients can experience lightheadedness, intolerance of exercise, fatigue, visual blurring, weakness, imbalance, headaches, shakiness, clamminess, anxiety, shortness of breath, and mental fogginess.
It has now been established that there is a substantial overlap between syndromes of orthostatic intolerance on the one hand, and either chronic fatigue syndrome (CFS) or fibromyalgia (FM) on the other. It needs to be emphasized that not all those with POTS have CFS or FM, and not all with CFS or FM have POTS.