Thread by @mecfsskeptic

1) A new blog post about the problems with the criteria for Postural Orthostatic Tachycardia Syndrome (POTS).

It’s quite a long read, so I’ll try to summarize the main ideas in this thread.
mecfsskeptic.com/the-problems-w…

2) ARGUMENT 1: heart rate increases upon standing > 30 bpm are far from abnormal.

In this study of the general population, for example, more than half of healthy young adults had an increase higher than the POTS threshold.
pubmed.ncbi.nlm.nih.gov/31476713/

3) Other studies found similar results. In the one below the median heart rate increase was 28 bpm in 120 participants aged 14 to 76 years.
journals.physiology.org/doi/full/10.11…

4) In an older German study the mean HR increase after 2 minutes of standing was 29 bpm. “In comparison with the previously published diagnostic limits for POTS, the reference values based on our population appeared to be [...] higher”
pubmed.ncbi.nlm.nih.gov/8924754/

5) We see the same results in adolescents: the 40 bpm threshold used in this age group is not really abnormal either.

In the study below 10% had an HR increase above 39 bpm, and 2.5% above 52.7 bpm.
pubmed.ncbi.nlm.nih.gov/21996154/

6) Another study examined 307 public high school students and found that the 97.5 percentile was not 40 but 48 bpm.

An older study from Hawaii reported that “a healthy adolescent may have an orthostatic heart rate increase of 40 to 50 beats per minute.”
journals.sagepub.com/doi/10.1177/08…

7) The reference data used to justify the 30-bpm threshold comes from POTS pioneers Dr. David Streeten and Dr. Philip Low during the 1980s and 1990s. However, they used shorter test durations (1-3 minutes) and did not adjust for age differences.

8) ARGUMENT 2: Most people with orthostatic intolerance (OI) do not have POT, whether you look at ME/CFS, Long Covid or patients referred to an autonomic clinic.

In ME/CFS the majority of patients (62-92%) have OI symptoms while a small minority (ca. 20%) has POTS.

9) ARGUMENT 3: The correlation between POT and OI is weak. Symptom severity often correlates poorly with the magnitude of postural tachycardia.

10) One study of the general population, for example, found that: “there was no significant correlation between […] heart rate increment on HUT [Head-Up Tilt] and symptoms of orthostatic intolerance.”
pubmed.ncbi.nlm.nih.gov/23766503/

11) Another study noted: “One cannot predict which seemingly healthy adolescents will have high heart rate changes based on orthostatic symptoms.”
journals.sagepub.com/doi/10.1177/08…

12) Other studies divided OI patients into those that met the heart rate threshold of POTS and those that didn’t and found no significant difference: “There are […] no clinical differences between patients as a function of HR increase during standing”
pubmed.ncbi.nlm.nih.gov/31385108/

13) Some ME/CFS studies also report that “orthostatic tachycardia did not account for OI symptoms in CFS” or that “POT was not associated with OI to an appreciable extent.”

ncbi.nlm.nih.gov/pmc/articles/P…
sciencedirect.com/science/articl…

14) Because of the weak correlation, moving the threshold up likely won’t help much.

One study found that moving it to 38 bpm would mean that 27% of healthy controls would still exceed it while 20% of POTS patients would no longer meet it.
pubmed.ncbi.nlm.nih.gov/22931296/

15) ARGUMENT 4: Heart rate increases after standing are influenced by many factors including sleep, salt and fluid intake, and deconditioning. There is almost no data on reproducibility.

16) Some studies suggest that a single test is not reliable. An ME/CFS study found that of the 7 patients who had POTS on a good day, 4 (55%) did not have it on a bad day. Of the 17 patients who did not have POTS on a good day, 8 (47%) had it on a bad day
pubmed.ncbi.nlm.nih.gov/26374335/

17) For a more thorough discussion, see the blog.

Did you spot errors or find data that supplements or contradicts some of the statements in the blog? Feel free to reach out at ([e-mail]).

Thanks in advance!
mecfsskeptic.com/the-problems-w…