In the fifth web seminar produced by the ME/CFS Association in the Netherlands is by Dr. Visser, a Dutch cardiologist. He takes on Postural Orthostatic Tachycardia Syndrome (POTS).


POT refers to abnormally high heart rates in response to standing. The prevalence of POTS in chronic fatigue syndrome is unclear.

POTS refers to an overly rapid increase in the heart rate that occurs upon standing.  POTS, which was first described in the 1990s, is a relatively new disorder, but in the last three years a tremendous flood of research has occurred.  In fact, forty percent of all POTS publications have been published in the last three years.

POTS is currently diagnosed when your heart rate increases 30 bpm on a tilt table test. For children the cutoff criterion is 40 bpm.

POTS, Dr. Visser said, occurs in fibromyalgia, MS, and a ‘tremendous’ number of other disorders (including hyperventilation… hmmm) as well as chronic fatigue syndrome. More connections and causes will undoubtedly be discovered in the future.

(Recently we saw that problems with the ‘chemoreflex’ that regulates CO2 levels in the blood can cause POTS. Other causes include blood pooling in the legs upon standing.  Both result – in one way or another – in reduced blood flow to the brain.)

Wide Variability in Prevalence Estimates in Chronic Fatigue Syndrome

Visser noted that studies suggest from 10 to 40 percent of people with ME/CFS meet the criteria for POTS. Visser’s own personal extensive (unpublished) studies, however, have found it in about 5 percent of his patients. Visser suggested that ‘inclusion bias’ — i.e. people with POTS symptoms showing up more in some practices than others — may be causing the wide prevalence estimates.

(Dr. Natelson has found a much higher incidence of POTS in adolescents with ME/CFS than in adults. I asked him if POTS in adolescence was turning into orthostatic hyperventilation in some adults. Natelson stated he believes ME/CFS in young people is a different disease than found in adults:

I believe CFS in young people is a different disease from that occurring in older adults. The prognosis for kids and adolescents is much better than for older folks.  Their biology is much more reactive too, so that may be why.  In kids, finding both POTS and orthostatic hyperventilation is not uncommon.“)

Dr. Visser on POTS

A presentation at a recent conference suggested that many people who have significant increases in heart rate upon tilting, but who do not meet the criteria for POTS, would test positive for POTS if the tilt table test were run again.  This suggests, of course, that many more people should receive a POTS diagnosis than currently do.


As Dr. Visser aptly stated, when your heartbeat rises from 60 to 150 beats per minute, you’re going to feel something.  The first thing you’ll notice will be palpitations – but also commonly dizziness, lightheadedness, nausea and other symptoms.

Cognitive problems, not surprisingly, rank high among the symptoms caused by a disorder which is characterized by reduced blood flow to the brain. (Note that the high heart rate often appears to be the body’s attempt to fix the real problem, which is a sudden loss of around 30% of the normal blood flow the brain.)


The number of different things that can cause it complicates how to treat POTS.  One general recommendation is staying adequately hydrated to keep your blood volume up.

Beta blockers can reduce the rapid heart rate and sympathetic nervous system activation and a variety of other drugs are available. It generally comes down to a process of trial and error to see which drugs work best.

Long Term Complications Affecting the Heart

The heart must be a pretty darn resilient organ. While noting that the issue has not been extensively researched, Dr. Visser stated ‘there is no indication at all’ that a fast heartbeat occurring over a long period of time can damage it.

Blood Flow and the Brain

The Dizziness – The Underappreciated Symptom

dizzy person

Visser finds high rates of dizziness/lightheadedness in his patient – and thinks the symptom should get more attention

One of the first things that struck Visser, a cardiologist, about chronic fatigue syndrome was the high rate of dizziness found, not just when patients with ME/CFS stood up, but when they were standing or walking or after exertion (definitely including mental exertion).

Dr. Visser believes that a symptom that strikes 50% of the people with ME/CFS should get more respect, and he lamented that it was mostly buried in the Canadian Consensus Criteria.

Given that dizziness is usually associated with reduced blood flow to the brain, the question becomes what’s stopping enough blood from getting to the brain. Visser noted that the cranial nerves might not be getting the right message regarding blood flow. There’s also the problem of low blood volume, and there’s the problem of blood pooling in the legs and abdomen that traps the blood in the lower body, keeping it from getting to the brain.

Measuring the amount of blood flowing to the brain can be expensive and complex (SPECT, MRI, PET scan) but Visser uses a simpler and less expensive method called echoscopy. Visser showed an image that indicated much reduced blood flow (a 23% reduction) to the head upon tilting – something he called ‘considerable’ and a much greater reduction than found in healthy people.

Dr. Visser on Low Blood Flows to the Brain

Visser’s many examinations done on patients lying down, sitting up, and standing revealed that just sitting up resulted in a 12% decline in blood flow to the head, while standing knocks blood flow down 18%, and the tilt table 19% – much greater declines than in healthy people.


chart showing decline

Substantial declines in blood flows to the brain were the norm when people with ME/CFS sat or stood up…

What can be done about reduced blood flow to the brain (and the resulting dizziness, lightheadedness, etc.)? (Standing on one’s head :) ). Unfortunately, according to Dr. Visser there are ‘absolutely no drugs’ that can enhance blood flow within the brain and he noted if you are experiencing dizziness you should be careful that you don’t end up fainting (and hurting yourself).


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