Exercise - Treatment or Cure?
8th September 2018
An exercise routine designed for astronauts can improve the symptoms of PoTS to the extent that some patients are no longer classified as having the condition and can get back to normal lives, says US cardiologist, Professor Benjamin Levine.
Professor Levine has worked extensively with NASA examining the effects of spaceflight on the heart and circulatory systems of astronauts, and he sees an overlap with PoTS patients.
“POTS is fundamentally a problem of gravity”, says Professor Levine, director of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital in Dallas. “Two out of three astronauts can’t stand up after they’ve spent even a short time in space, and all of them have very high heart rates when they attempt to stand. This observation got us thinking whether there might be common threads between the adaptation to spaceflight and patients with POTS”
This video shows an astronaut fainting after spaceflight. (Warning - Some people with PoTS may find this video distressing)
In the zero-gravity of spaceflight an astronaut’s heart has less work to do. It becomes ‘deconditioned’ and literally shrinks, losing heart-muscle mass, especially in the left ventricle, which has the job of pumping blood all round the body.
A horizontal exercise programme to help astronauts recover on their return to earth was developed by Professor Levine, who also holds the Distinguished Professorship in Exercise Sciences at UT Southwestern Medical Center in Dallas. Endurance exercise – the repetitive use of large muscle groups - is what is needed to make the heart increase in size, he says.
But upright exercises such as running are difficult or impossible for a returned-astronaut who feels faint when standing. So his programme for astronauts is based on semi-recumbent exercises such as rowing, swimming and recumbent cycling. Rowing is the endurance exercise that most increases the mass of the heart, he says.
Professor Levine reasoned that his patients with PoTS might also benefit from the programme. “The archetypal PoTS patient is someone who is quite high functioning – in some cases, even a competitive athlete or a dancer. Then something happens – it could be an injury or an illness – but it puts them to bed,” he says. When they recover from whatever put them to bed, they find they get symptoms such as a high heart rate and dizziness when they stand up, he says. They lie down again because standing is so symptomatic, but that only makes matters worse. “It’s a downward spiral,” he says.
A small heart?
Professor Levine thinks the root cause of PoTS is a heart that pumps out a smaller-than-normal stroke volume (the volume of blood pumped out with each beat). When the stroke volume is small, there is a normal reflex response produced by the sympathetic nervous system that causes the heart rate to increase, he explains.
The people most susceptible to PoTS may be those who naturally have small hearts, he says, which might be one reason why women are more prone to PoTS than men. Women have smaller hearts than men of the same height. But even people with normal-sized hearts can lose heart mass, and have a decreased stroke volume as a result of bed-rest, he says.
“If the underlying problem is that the heart is too small, then, if we make the heart bigger, the syndrome should go away. And the only way to make the heart bigger is with exercise training,” says Professor Levine.
Professor Levine has carried out the leading studies on exercise for PoTS [1, 2, 3, 4, 5], and the majority of the people who completed his programme recovered to the extent that they were no longer classified as having PoTS – but many others dropped out along the way.
“I get emails from patients around the world thanking me for ‘giving me their life back’,” he says.
His theory that the underlying cause of PoTS is a small heart is contentious. He and the co-authors of his research had some complaints from patients offended by his suggestion that PoTS should be called ‘the Grinch Syndrome’ after the Dr Seuss character whose heart was ‘two-sizes too small’.
Professor Levine is sorry that this caused distress to patients. He says he uses this analogy as a mnemonic for other doctors to focus their attention on the low upright stroke volume, and in no way should it be interpreted that he believes PoTS patients are lazy, or mean spirited.
“Quite the contrary,” he says. “The vast majority of my patients are dedicated and committed women who feel badly, and are looking for help.”
Meanwhile some experts think that, while a small or deconditioned heart may play a role in the development, exacerbation or continuation of PoTS in some patients, it is not necessarily the whole story. In an editorial discussing one of Professor Levine’s publications, PoTS expert, Dr Satish Raj of the University of Calgary cautions that: “Exercise is a treatment...not a cure ”
Nevertheless Professor Levine contends that, regardless of what the underlying cause of PoTS might be in an individual patient, much of the functional disability associated with the syndrome is exacerbated by cardiovascular deconditioning, and he believes many patients will feel better with a focused, dedicated exercise training program.
For an examination of the evidence that exercise is helpful, at least for some PoTS patients, and details of Professor Levine’s research, and how to do his exercise programme please see Exercise for PoTS - what’s the evidence?
©Clare Pain 2018
- Qi Fu et al. Cardiac origins of the postural orthostatic tachycardia syndrome. Journal of the American College of Cardiology, 2010. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2914315/
- Shigeki Shibata et al. Short-term exercise training improves the cardiovascular response to exercise in the postural orthostatic tachycardia syndrome. Journal of Physiology2012. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3547265/
- Qi Fu et al. Exercise Training versus Propranolol in the Treatment of the Postural Orthostatic Tachycardia Syndrome. Hypertension, 2011. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142863/
- Qi Fu et al. Exercise in the Postural Orthostatic Tachycardia Syndrome. Autonomic Neuroscience, 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4336603/
- Stephen A George et al. The international POTS registry: Evaluating the efficacy of an exercise training intervention in a community setting. Heart Rhythm 2016. https://www.heartrhythmjournal.com/article/S1547-5271(15)01527-1/fulltext
- Satish R Raj. Row, row, row your way to treating postural tachycardia syndrome. Heart Rhythm, 2016 https://linkinghub.elsevier.com/retrieve/pii/S1547-5271(15)01674-4