Postural Orthostatic Tachycardia Syndrome (POTS) and other forms of dysautonomia (dysfunction of the autonomic nervous system, which regulates breathing, heart rate, blood pressure, kidney function, and all the other things you don’t have to think about) are commonly comorbid with mast cell disorders and EDS. The "chicken and egg" discussions of mast cell reactions and POTS symptoms could fill many websites like this with very little agreement reached by the end.
Fortunately, POTS diagnostic criteria are rather simple—a heart rate increase of 30 beats per minute or more, or reaching over 120 beats per minute shortly after moving from a reclined position to a standing position —and it is often diagnosed by a “poor man’s” tilt table test, with blood pressure and heart rate measurements being taken while a patient is fully reclined, sitting, and standing. Some POTS patients have also been previously diagnosed with “low blood pressure” or orthostatic hypotension.
However, POTS symptoms are significantly more varied, and they often coincide with or worsen (or, more often, visa versa) mast cell reactions. With or without the more “obvious” syncope (fainting) or lightheadedness, which often leads to primary POTS diagnoses if adolescents around growth spurts, many POTS patients have low blood volume, nausea, cold hands or feet, shaking, exercise intolerance, heat intolerance, heart palpitations, headaches, heart “pounding,” excessive fatigue, small fiber neuropathy, difficulty concentrating, chest pain, and blood pooling, among other symptoms. POTS is especially prevalent among women of childbearing age, and many find that menstruation worsens their symptoms.
Like the other conditions discussed here, POTS affects different patients in varying ways and degrees of severity, patients’ symptoms are often mistakenly chalked up to anxiety (or, by some especially doofusy doofuses, “laziness”), coping strategies are important but also vary by patient and, in my observation, the cardiologists who know most about it are among the least likely to claim they are “POTS specialists,” which can make finding a competent practitioner a challenge.
Avoiding heat and other stressors, finding safe forms of exercise, preventing quick changes of posture, using wheelchairs (or fully reclining) when necessary, and maintaining electrolyte balance and blood volume are often crucial to symptom management, though POTS remains enormously frustrating and often debilitating. Dysautonomia International estimates that about one in four POTS patients are unable to work due to the condition. In trifecta populations, POTS symptoms arising from mast cell reactions are naturally most common, so mast cell treatment is of primary importance.
To make matters more complicated, the beta antagonists (propranolol and others) many cardiologists are keen to prescribe (since these lower heart rate)for cases they assume result from primary POTS are contraindicated in the management of these cases. (See this question in the FAQ.) I am less familiar with the use of corticosteroids like fludrocortisone (which causes increased water retention) and vasopressors like midodrine (which constrict blood vessels, thereby increasing blood pressure) in the treatment of trifecta patients but have observed that several do find mast cell treatment in general improves or eliminates their symptoms, and some also report dramatic improvement from low dose naltrexone. Those who do not or who are in fact suffering from primary POTS, unrelated to these disorders may benefit from a number of other cardiac drugs.
There are several other types of dysautonomia, many of which share overlapping symptoms and sometimes what seems like pre-Flinestones-level distinctions and genetic excitement. You can learn more about all of them at Dysautonomia International.