POTS is a condition characterized by very rapid heart rates (>40 bpm increase – adolescents; 30 bpm increase – adults) and pooling of blood in the lower body while standing.  It has strikingly similar symptoms (fatigue, exercise intolerance, dizziness, nausea, pain, cognitive issues)  to chronic fatigue syndrome (ME/CFS) and fibromyalgia, and is often triggered with a flu-like illness. As with ME/CFS and FM, most people with POTS are female.

knocked-outThe idea that postural orthostatic tachycardia syndrome (POTS) is a heterogeneous condition is not new at all.  All types of POTS are characterized by increased heart rates upon standing but the underlying physiology differs greatly.

  • Neuropathic POTS – caused by decreased vasoconstriction of the blood vessels in the legs and/or abdomen causing blood to pool in the lower body upon standing. Not associated with autoimmune issues according to a 2014 review. Treatment is focused on improving circulation with exercise and vasoconstricting drugs such as Midodrine, droxidropa and Mestinon (pyridostigmine)
  • Hyperadrenergic POTS – associated with increased sympathetic nervous system activity which can be caused in multiple ways. Treatment includes exercise, beta blockers and possibly angiotensin receptor blockers and droxidopa.

Exercise has been used in many studies to understand chronic fatigue syndrome (ME/CFS), but nobody until recently has used exercise to try to understand POTS.  Exercise is a particularly interesting tool in the case of POTS because exercise intolerance is often present, and because like with fibromyalgia, exercise has become a kind of go-to therapy for POTS.

In these two studies researchers at the Mayo Clinic in Rochester, New York exercised adolescent POTS and ME/CFS patients (in one of the studies)  to exhaustion while measuring their heart rates, oxygen usage, anaerobic threshold, ventilation, gas exchange, etc. The hypothesis – POTS is a heterogeneous condition that is caused in several ways.  The goal – to elucidate different subsets.

Cardiac responses to exercise distinguish postural orthostatic tachycardia syndrome variants Paolo T. Pianosi1, Darrell R. Schroeder2 & Philip R. Fischer. Physiol Rep, 4 (22), 2016, e13040, doi: 10.14814/phy2.13040

High flow variant postural orthostatic tachycardia syndrome amplifies the cardiac output response to exercise in adolescents Paolo T. Pianosi, Adele H. Goodloe, David Soma, Ken O. Parker, Chad K. Brands & Philip R. Fischer. Physiol Rep, 2 (8), 2014, e12122, doi: 10.14814/phy2.12122

Adolescent Fatigue, POTS, and Recovery: A Guide for Clinicians Sarah J. Kizilbash, MD, Shelley P. Ahrens, RN, CNP, DNP, Barbara K. Bruce, PhD, Gisela Chelimsky, MD, Sherilyn W. Driscoll, MD, Cynthia Harbeck-Weber, PhD, Robin M. Lloyd, MD, Kenneth J. Mack, MD, PhD, Dawn E. Nelson, RN, MSN, Nelly Ninis, MD, MSc, MBBS, Paolo T. Pianosi, MD, Julian M. Stewart, MD, PhD, Karen E. Weiss, PhD, and Philip R. Fischer, MD. Curr Probl Pediatr Adolesc Health Care 2014;44:108-133

Three Flavors

The POTS  subsets were hidden at rest. Even the tilt testing – the standard protocol used to diagnose POTS –  failed to expose them. Only under the stress of exercise did the subsets show up.

Adolescent POTS patients may look very similar to each other outside but inside some very different problems are present. The differences in cardiac output found were staggering. In general, average cardiac output or Q should rise ~5–6 l/min during exercise. Most of the 209 patients in the study (70%) exhibited normal increases in cardiac output during exercise (5.5 l/min), but 15% of the group had very low cardiac output (2.25 l/m), and 15% had very high cardiac outputs (9.74 l/min).

The POTS patients with low cardiac output were called “hypokinetic”, while those with high cardiac output were termed “hyperkinetic”.  The others were termed normal.

Hyperkinetic – The high cardiac output seen in the “hyperkinetic” POTS group attempts to compensate for problems constricting their blood vessels. During exercise our blood vessels should narrow in order to develop enough pressure (perfusion pressure) to force more blood into our tissues. In the hyperkinetic group, however, their blood vessels remain open; instead the group kicks their heart output up in order to produce the needed perfusion pressure.

That compensatory effort – like so many compensatory efforts in the body – is not entirely successful. These patients get lots of blood flowing through their systems but still get reduced oxygen extraction at the muscles. The authors noted that the reduced oxygen extraction  could be due to metabolic issues but they believe is probably simply a blood flow problem. They characterized these patients’ muscles as starving in the land of plenty – and becoming fatigued because of it.

Unlike the hypokinetic group, these patients do not have problems with  blood volume or preload.

The Hypokinetic Group – Hypokinetic POTS  patients have the opposite problem; their low blood volume and decreased blood vessel capacity means they can’t increase their cardiac output. Instead, they tighten down their blood vessels in order to apply pressure.

In 2004 Stewart called this group of patients the “low-flow” group. Low blood volume clearly plays a major role. These patients’ low calf blood volumes, reduced venous capacitance and tightened down blood vessels left Stewart describing them as being “chronically vasoconstricted”.  The “muscle pump” that’s supposed to kick in to keep their blood from draining into their lower body when they stood isn’t working either.

This study indicates that this group of POTS patients also has reduced stroke volume (cardiac output) due to reduced preload. Reduced preload  – or the inability to fill the heart with enough blood to pump it out in normal amounts – is same problem that Systrom uncovered in his large exercise study of patients with unexplained exercise problems.

The only thing the body can do to combat a problem like this is to clamp down on the blood vessels in an attempt to build up enough pressure to get the blood to the tissues (e.g. perfusion pressure again).

A POTS Scenario

These are Mayo Clinic researchers; which means they’re big on exercise and deconditioning.  Their POTS scenario begins with a physiological problem and ends in deconditioning.

One scenario suggests that a dysfunctional renin-angiotensin system impairs the sympathetic nervous systems ability to regulate blood volume – and down the blood volume goes. At this point the muscles and heart are still working fine,

subsets

Exercise exposed three different types of POTS

but further sympathetic nervous system problems impair the ability of the blood vessels to tighten down and apply enough pressure to shoot the blood into the exercising muscles.

The fatigue and dizziness experienced cause POTS patients to pull back. As deconditioning sets in the  muscle pump drops out and the capacitance of the veins to store blood drops. That reduces preload to the heart, which produces smaller hearts and lower cardiac outputs.

It’s important to note that POTS is more than deconditioning. Problems with the blood vessels, blood volume or sympathetic nervous system functioning also abound but deconditioning adds significantly to the burden POTS patients experience.

The Chronic Fatigue Syndrome Adolescents

The changes seen in the adolescent ME/CFS patients – lower left ventricular mass and higher pulse –  were consistent with physical deconditioning and/or altered sympathetic-parasympathetic balance. The fact that they  did not display the increased cardiac output found in the hyperkinetic POTS patients indicated that they were fundamentally different from them.

While it’s hard to find a report which states when deconditioning begins (i.e. how much bed rest it takes) or the minimum level of activity necessary to stave it off (i.e. how many steps per day), deconditioning probably places its own special burden on many people with ME/CFS who cannot be active.

Many studies show evidence of sympathetic/parasympathetic (SNS/PNS) problems in ME/CFS and POTS, and the authors noted that the inability to reduce the heart rate to normal levels after exercise is indicative of parasympathetic nervous system failure.  In the end, though, the authors appeared to discard the SNS/PNS possibility in ME/CFS and simply stated that exercise “ought to be an effective remedy for” both POTS patients and ME/CFS.

Treatment Implications

fluids_for_cfsThe basics of POTS treatment are pretty simple; increase blood volume (increased fluid  – 65-80 oz/day) and salt intake), exercise to the extent possible (start off very low), avoid stressors and perhaps take appropriate drugs and use other aids (compression stockings).

The Mayo Clinic authors stress that deconditioning adds a further stressor to many POTS patients’ lives. They don’t appear to believe that exercise can cure most POTS patients but they do present the possibility that supine exercise might fix some of the circulatory issues that hyperkinetic or high blood flow POTS patients experience. Exercising in the supine position should allow POTS patients to direct more blood to their working muscles because they’re not experiencing blood pooling in their lower body.

The Gist

  • POTS is characterized by high heart rates upon standing which attempt to compensate for blood pooling in the lower body
  • Exercise stress tests exposed types of POTS that tilt tests failed to reveal
  • The high cardiac outputs and blood flows in hyperkinetic POTS patients attempt to compensate for a failure to vasoconstrict or tighten down their blood vessels when they stand.
  • The overly vasoconstricted blood vessels in hypokinetic POTS patients attempt to compensate for reduced blood volume, low venous capacity and reduced blood flows to the heart
  • The study suggested that deconditioning adds another burden to both adolescent POTS and ME/CFS patients.

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Ferritin – While exercise is a mainstay of many POTS patients treatment regimens, not all POTS patients can exercise. One young man failed to benefit from graded  exercise therapy until intravenous iron infusions boosted his ferritin levels significantly. Only after that happened was he able to exercise vigorously without relapsing.  Iron or ferritin levels are a relatively new addition to the equation in POTS and a Mayo clinic study is underway to assess its role.

Low flow or hypokinetic POTS patients suffering  from low circulatory capacitance, preload failure and possibly small hearts, definitely need to have their blood volume enhanced. Ways to enhance blood volume include an oral rehydration solution one can easily make at home which may rival saline solution in effectiveness.

The authors do not provide treatment recommendations but the study’s conclusions appear to suggest that

  • Vasoconstricting drugs such as midodrine, droxidropa and Mestinon (pyridostigmine) may be more helpful in hyperkinetic POTS patients
  • Blood volume enhancing drugs such as fludrocortisone, desmopressin and beta blockers (propanolol, metropolol, atenolol) which increase venous return to the heart might be more helpful in hypokinetic POTS patients

Neuromuscular Strain Impairing Ability to Exercise? – Dr. Rowe’s finding that adolescents with ME/CFS (and surely those with FM as well) experience pain when elongating their tendons during simple movements (let alone during exercise), throws another factor into the fire.

At the IACFS/ME conference, Rowe stated that special exercises to address the stuck tendon problems allowed adolescent patients to engage in more exercise.  We’ll cover that finding in the IACFS/ME Conference treatment blog.

 

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