In 2013, I looked at whether some bacteria may be causing postural orthostatic tachycardia syndrome in this [post] where Clostridium septicum is one species associated with tachycardia and another CFS symptom, hypotension (low blood pressure). In early 2016, I wrote about Ivabradine, a medicine that looked promising in this [post] as well as some vacines that can cause POTS in this [post].
- From Mayo clininc “Only 33 (19%) respondents reported complete resolution of symptoms… 2-10 years after diagnosis.” 
- “POTS can be mistaken for panic disorder, inappropriate sinus tachycardia, and chronic fatigue syndrome.” 
- “Apart from symptoms of orthostatic intolerance, there are many other comorbid conditions such as chronic headache, fibromyalgia, gastrointestinal disorders, and sleep disturbances. Dermatological manifestations of POTS are also common and range widely from livedo reticularis to Raynaud’s phenomenon….The most commonly reported symptom was rash (77%). Raynaud’s phenomenon was reported by over half of the patients, and about a quarter of patients reported livedo reticularis. The rash was most commonly found on the arms, legs, and trunk. ” 
- “Many patients with POTS also report symptoms not attributable to orthostatic intolerance, including those of functional gastrointestinal or bladder disorders, chronic headache, fibromyalgia, and sleep disturbances. In many of these cases, cognitive and behavioral factors, somatic hypervigilance associated with anxiety, depression, and behavioral amplification contribute to symptom chronicity.” 
- “Numerous symptoms such as excessive tachycardia, lightheadedness, blurry vision, weakness, fatigue, palpitations, chest pain, and tremulousness are associated with orthostaticintolerance. Other co-morbid conditions associated with POTS are not clearly attributable to orthostatic intolerance. These include chronic headache, fibromyalgia, functional gastrointestinal or bladder disorders, cognitive impairment, and sleep disturbances.” 
- ” Other observed dermatological manifestations of this systemic disease include Raynaud’s phenomenon, koilonychia, onychodystrophy, madarosis, dysesthesia, allodynia, telogen effluvium, increased capillary refill time, and livedo reticularis. The treatment of this disease poses a great challenge. The author reports the unprecedented use of an oral angiotensin II type 1 receptor antagonist [Losartan] resulting in remarkable improvement.” 
And the gut bacteria aspect is clear:
- “The most commonly reported GI symptoms were nausea (86%), irregular bowel movements (71%), abdominal pain (70%), and constipation (70%). Additionally, 82% of patients reported having GI symptoms more than once per week, and 71% reported having seen a GI specialist, and symptoms did not improve with changes in position….GI disturbances are common, frequent, and prolonged in patients with POTS, likely impacting quality of life. Given the importance of the enteric nervous system to normal GI functioning, the same autonomic impairment leading to POTS may result in abnormal gut motility and ultimately subjective GI discomfort.” 
- “Over 70 % of patients had nausea and/or vomiting, which was the most common GI symptom; other common symptoms were abdominal pain (59 %), bloating (55 %), and postprandial fullness/early satiety (46 %). Over one-third of patients had abnormal [i.e., rapid (27 %) or delayed (9 %)] gastric emptying.” 
- “Two-thirds of patients with POTS and GI symptoms had abnormal, most frequently rapid gastric emptying.” 
- “Nonorthostatic symptoms included dry eyes or mouth, gastrointestinal complaints of bloating, early satiety, nausea, pain, and alternating diarrhea and constipation. Half of the patients reported an antecedent illness presumed to be of viral origin.” 
And mast cell involvement in some patients:
- “Mast cell activation+POTS patients were characterized by episodes of flushing, shortness of breath, headache, lightheadedness, excessive diuresis, and gastrointestinal symptoms such as diarrhea, nausea, and vomiting. Triggering events include long-term standing, exercise, premenstrual cycle, meals, and sexual intercourse.” 
- ” POTS is a “final common pathway” for a number of overlapping pathophysiologies, including an autonomic neuropathy in the lower body, hypovolemia, elevated sympathetic tone, mast cell activation, deconditioning, and autoantibodies. Not only may patients be affected by more than one of these pathophysiologies but also the phenotype of POTS has similarities to a number of other disorders, e.g., chronic fatigue syndrome, Ehlers-Danlos syndrome, vasovagal syncope, and inappropriate sinus tachycardia.” 
Microbiome Data is Still Lacking
“POTS, which often accompanies ME/CFS, is a fainting disorder associated with an abnormal increase in heart rate and low blood pressure. The mechanism is unknown, but some people develop it after contracting viral or bacterial infections like mononucleosis, pneumonia or Lyme disease…. found two blood-borne microbes — Human Herpesvirus-4 and the coxsackie virus — known to cause chronic disease and POTS. Though Montoya wasn’t sure if these viruses were at the root of Erin’s illness or merely collateral infections, he started her on a high dose of the antiviral drug famciclovir.” [Stanford 2014]
Losartan is cited in one study as being effective, it has risks to it. This drug has a major impact on S. Aureus (the bacteria that keeps showing up connected to CFS!!), but zero impact on E.Coli.  In other words, it’s antimicrobial profile matches what my model would deem to be a very good candidate.
On my wish list is for a research MD to do microbiome analysis of a large set of POTS patients, and have this data, with co morbid conditions analyze by a good machine learning program – the results may give a nice bacteria strain to symptoms mapping.