Recently, a few readers with Postural Orthostatic Tachycardia Syndrome (POTS) brought to my attention an article that was published a couple of years ago in the Journal of the American College of Cardiology on POTS. They are disturbed by the article's conclusions, noting that it is hard enough to live with this condition without well-meaning academics inventing insulting names for them, and inappropriately suggesting that POTS sufferers have brought the condition upon themselves. They asked me to comment on it.
The article comes from the lab of Dr. Benjamin D. Levine MD, from the University of Texas Southwestern Medical Center. Dr. Levine's group studied 27 patients with POTS who had been referred to his center. In this meticulously-conducted study, the chief findings were: 1) None of these patients had measurable abnormalities in their autonomic nervous system. 2) Many (about 70%) of the the patients with POTS had small hearts and low blood volume, findings characteristic of deconditioning. And 3) On average, patients with POTS responded very favorably to a prolonged, graded program of exercise therapy.
The authors concluded that POTS is "per se" a condition caused by deconditioning and not dysautonomia, and subsequently promoted in several major media outlets the new name they proposed in this peer-reviewed publication for this already-well-named condition, to wit: Grinch Syndrome (because grinches, according to definitive sources, have small hearts).
My correspondents who have POTS do not argue with the study's results, but strongly object to the conclusions which the authors derive from those results. In addition to the obvious desire of not wishing to be referred to as grinches, they point out that attributing all cases of POTS to deconditioning (which the authors explicitly do) is not only wrong, but likely harmful to POTS sufferers.
A small heart and low blood volume are characteristics of deconditioning. If you take healthy young people and put them at bed rest for a week or so (or astronauts and put them in weightless space for a similar period of time) they will become deconditioned. They will often develop reduced heart size and blood volume, and symptoms very similar to POTS. And they also improve with graded exercise.
It is undoubtedly true that the vast majority if not all people with significant POTS are deconditioned. You would become deconditioned too if you could not stand up without becoming extremely lightheaded, or passing out. And it is indeed this fact which this study confirmed.
But the fact that patients with POTS might be shown to have deconditioning does not prove (and in fact, it does not even strongly suggest) that deconditioning is the cause of POTS, rather than the result.
And while this study did not find signs of dysautonomia in its patients, it must be noted that it was conducted in a single tertiary referral center - which typically means that referral patterns have been filtered by time, tradition and experience, and it certainly means that its patients were screened (twice) prior to referral. In addition, the study explicitly excluded patients who had a diagnosis of autonomic dysfunction. Furthermore, the authors themselves note in their discussion that numerous other studies from other institutions have documented significant autonomic dysfunction in patients with POTS - an observation which seems not to square with their conclusions. It seems quite apparent that the authors, probably inadvertently, studied a particular subset of the broad universe of patients with POTS.
Further, the study fails to account for (or even address) the fact that POTS, as is characteristic of all the dysautonomias, often occurs in active, athletic people, and often has a very sudden onset, without any preceding period of prolonged inaction (or any inaction at all) which could produce deconditioning.
Finally, the authors do not comment on the fact that, whereas people with typical deconditioning respond quite rapidly to a graded exercise program (most often improving markedly over a period of a few days), those with POTS - even the ones who end up with a very favorable response to exercise - tend to improve at a relatively glacial pace, over a period of weeks or months. Similarly, once recovered, patients with simple deconditioning do not deteriorate with normal daily living; in contrast, those with POTS who improve with exercise often relapse quickly if they discontinue their program of frequent (usually daily) aerobic exercise.
It seems far more likely from the available data (including the data presented in this otherwise excellent study) that the deconditioning seen in POTS is most often a secondary phenomenon that will naturally follow from having POTS, instead of the thing that caused the POTS in the first place.
So why is this distinction such a big deal?
It is because people who are diagnosed with POTS already have an extraordinarily difficult time getting their doctors and families to take their symptoms seriously. They often go through a prolonged ordeal of being told by several doctors that they have anxiety or depression or some sort of conversion reaction rather than a true, physiologic condition. It is often weeks or months, and occasionally years, before some physician finally figures out the true diagnosis.
And now, even after the correct diagnosis is made, they face the prospect of being regarded as having brought the condition on themselves, due to "deconditioning," which is often medical talk for being too sedentary, passive, and lazy. And when their family is told that the problem is self-induced, via the mechanism of sloth, and is told this by a doctor no less, the amount of support POTS sufferers are likely to receive from loved ones, at the very time they are fighting to recover and are most in need of it, will predictably diminish.
And hence, the conclusion that POTS is caused by deconditioning is not only unsupported by the results of this study, but is also likely to be harmful to people who have POTS. I have to agree with my correspondents that the authors indeed seem to have done their patients a disservice.
So who's really the grinch here?
Fu Q, VanGundy TB, Galbreath M, et al. Cardiac origins of the postural orthostatic tachycardia syndrome. JACC 2010;55:2858-68.