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Dizziness only when horizontal
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Dizziness only when horizontal

Hello - has anyone ever become dizzy/felt faint only when horizontal?  My daughter has been given a tentative diagnosis of NCS (a full cardiology workup was normal), but the only time she ever feels that way (and has never actually fainted) is during a hard set at swim practice when she is horizontal and actually swimming - not when she is getting out or is vertical suddenly or anything else I've read about here.  I don't completely understand how that could be NCS because I thought by definition the faintness/fainting was from blood pooling in your legs, yet how could that happen when she is horizontal in the water and her blood is pumping vigorously from exercise?  Thanks.
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Neurocardiogenic syncope involves a neurological reflex whereby parasympathetic tone and sympathetic tone change to varying degrees to conspire to result in loss of consciousness. In layman's terms, the answer to your question is that no, blood pooling in the legs is not strictly causal of NCS (also known as vasovagal syncope).

Here is a very technical journal article on classifying different types of vasovagal syncope:


and a less technical explanation from wikipedia:

"resulting in simultaneous enhancement of parasympathetic nervous system (vagal) tone and withdrawal of sympathetic nervous system tone.
This results in a spectrum of hemodynamic responses:

1. On one end of the spectrum is the cardioinhibitory response, characterized by a drop in heart rate (negative chronotropic effect) and in contractility (negative inotropic effect) leading to a decrease in cardiac output that is significant enough to result in a loss of consciousness. It is thought that this response results primarily from enhancement in parasympathetic tone.

2. On the other end of the spectrum is the vasodepressor response, caused by a drop in blood pressure (to as low as 80/20) without much change in heart rate. This phenomenon occurs due to vasodilation, probably as a result of withdrawal of sympathetic nervous system tone.

3. The majority of people with vasovagal syncope have a mixed response somewhere between these two ends of the spectrum."

This all leads to the question of what test was used to diagnose your daughter with NCS? (I see you mentioned that a full cardiology workup was normal. I presume something came back abnormal to lead to this diagnosis?) Has she had a Tilt Table Test yet? It would be pretty uncommon but not out of the question for what your daughter is experiencing to fit under the diagnostic umbrella of NCS; I would question the diagnosis if it is not backed by findings such as a positive TTT and/or other cardiac or autonomic testing.

If I were you, I would be looking to rule out all other explanations for her symptoms at this time, in addition to seeking confirmation of this diagnosis. Anemia, low ferritin levels, etc. can cause similar symptoms, and extensive blood work should be done, not just a basic CBC. Electrolytes need to be closely examined and, if possible, radionuclide blood volume testing performed. Hypovolemia is another possible explanation. Google "iso-osmolar" beverages to find out what is optimal for keeping hydrated and what isn't; athletes can become dehydrated if the beverages they are using to rehydrate aren't right. (That's why sports drinks are preferable to plain water, but even some of those aren't as good as some "recipes" you can mix up at home or other formulations commonly used for digestive conditions, like pedialyte.) If her skeletal muscles are commanding her bloodflow when she exercises hard, and there's not enough to go around, that could cause lightheadedness/dizziness.

One test I would *highly* recommend given the context of her symptoms is an exercise stress test, particularly a VO2 max or "cardiorespiratory" stress test. That should give you more information on what is happening when she exerts herself.

Best, and I hope you will update us as well as let us know any further questions you have!

Thanks for all the suggestions!  Yes, I agree that all these other things needs to be ruled out.  You may have seen in my earlier posts in the fall that she has signed to swim at a Div. I school in the fall, and we cannot send her off with this vague, possibly incorrect diagnosis and no real help for it.

You asked about how she was diagnosed:  basically because they ruled out cardiac issues and her bloodwork was normal, and the old "teenage girls just faint a lot" diagnosis of exclusion, no definitive test that I know of.  She was under a lot of stress and not getting enough sleep in the fall when it started, and had caught a cold from being worn down.  So in that sense those might have been triggers if it is NCS.  I am picking up a copy of her bloodwork Mon. to see just what was tested.  I was told that her thyroid, electrolytes, hemoglobin (14), blood sugar, WBC, all were normal, but I don't know if things like adrenal function or the more complex thyroid tests were done.  They have not done a TTT, and when I asked about it, I was told that it wasn't necessary - it would just confirm what they already knew, although I kind of question if she'd have a positive response to it given it only happens when she's exercising.  She had a stress test on the treadmill - is that what you were referring to?  It was completely normal, but as I told them beforehand and they assured me they would account for, 15 minutes running on a slightly elevated treadmill for an athlete in her condition is nothing.  Her oxygen levels stayed consistent and high throughout.  She wore a monitor for a week, but obviously had to take it off to swim, therefore never capturing anything.  Her bp is consistent from lying to sitting to standing so she doesn't have any of the POTS issues.

One puzzling thing is she has actually been doing well with the supposed NCS - no dizziness in 6-8 weeks - trained well through Christmas break - then she had a sudden, dramatic decrease in performance two weeks ago at a meet, like dropping off a cliff or hitting a wall, and has continued to feel tired while swimming and do poorly, but feels fine out of the pool.  It fits the signs of overtraining, which she had a little bit of a problem with a few years ago.  I've read that overtraining can actually trigger dysautonomia, and of course dys. can lead to exercise intolerance - chicken and the egg.  She is resting and just swimming a little without really elevating her heart rate and seems to be making some progress.

A few things we have done on our own to avoid NCS triggers or that she HAS always done that address possible other problems:  we thought we saw some correlation in dizziness with her period, so she started on birth control pills a month ago, she eats frequently and very well - good balance of protein and healthy carbs, and she is well hydrated always.  During practice she drinks both water and Gatorade (and I will google the term you mentioned regarding sports drinks).  That leads to a question, though:  I have wondered if she could be TOO hydrated, and washing too much sodium out of her system?  The ped. said no, that because her electrolytes were normal, her body has adjusted to the amount she drinks.  But she drinks a LOT (mostly water - I'd worry about diabetes if her blood sugar wasn't normal) - we counted one day, and although it was a two practice day which called for more fluids, she had about 180 ounces!  The ped. said not to worry about it, though.

We were blown off by a neurologist in the fall, so I asked for a referral to the pediatric neuro in town, and her appt is finally on Tues.  I don't think he has any particular expertise in this area so I'm not expecting miracles, but I'm just hoping he'll take us a little more seriously and see that we just cannot send her off to collegiate training in the fall not having a confirmed diagnosis and not knowing when and what will trigger a problem or a crash.  And what if it IS something else simple that could be easily addressed?  I will ask about some of the things you mentioned.  Is it always a cardiologist who treats NCS even though it's related to the autonomic nervous system?  Or do some neuros?

Also, do you know if Vanderbilt ever takes anyone under 18, like especially if by the time we could probably get an appt (from what I've read) she'd be just a couple of months shy of 18?  That is by far the closest of the renowned places to us.  I know there are people on here battling terrible issues related to NCS that she isn't, so I don't know if one of those places would even see her, but I don't know if anybody around her really knows to diagnose it other than just throwing a label on it because they can't think of anything else.  It'd be a shame to potentially have a collegiate career ruined over something that might be easily addressed.  Thanks for any other direction you can provide!
I may skip around a bit here; sorry for that. I just got out of the hospital myself and am not fully "there" yet.

Drinking 180 oz in one day would be about 5 1/2 liters. (I can do this more easily in liters, because that's usually how the fluid-loading recommendations are given by dysautonomia specialists.) You may be surprised to hear that for sedentary (even bedridden) adults with dysautonomia such as NCS and POTS, fluid-loading recommendations can range from 3 to 5 liters of fluids per day! I don't know how that scales down to different sizes of children. (For adults there often seems to be little consideration to body size at least initially; many treatment centers have a standard handout with their one-size-fits-all volume recommendation, and will simply tell a patient to drink more/less depending on how things look at followup.) I would wager, though, that for a 17 y.o. athlete, 5.5 liters in one day is not at all unreasonable. As I mentioned above, iso-osmolar fluids would be superior to plain water (even if your physician is not aware of this ... dysautonomia is not well-known stuff); the reason for this is not merely to address electrolyte levels, which her doctor was wise to think of. With iso-osmolar fluids, you get the most optimal absorption of the fluids from the gut; in short, more of what you take in goes toward plumping up blood volume (i.e. alleviating the symptoms of NCS) rather than ending up passing right through her. I just watched a webinar on this, and I'm very hopeful that it will help me, actually. For example, I currently fluid-load 4 L/day (I'm rather sedentary, especially considered to your daughter, though!) but when I calculate based on the chart in the webinar, I should need less than 2.5 L in iso-osmolar fluids. Although I salt-load as well, I've been taking my salt and my fluids separately, and from what I understand here ... well, I don't think this has been the correct strategy; I know from my test results that it certainly isn't correcting my hypovolemia.

Here is the address to view the archived webinar. I highly recommend it, even if dysmotility isn't an issue in particular, as it still gives insight on how different fluids are absorbed from the gut (and thus how they affect your body's fluid volume). (Some browsers, such as Chrome, will simply view a pdf unless you specifically initiate a download. Be aware that some browsers do not have this capability built in, and going to this URL will automatically initiate download of the powerpoint slides from the webinar.)


There are different kinds of stress tests: nuclear stress test, stress echo, VO2/cardiopulmonary stress test, and there may be others of which I'm not aware. All of these can be done on a treadmill as you described. The one I recommended was a VO2 max (aka cardiopulmonary stress test). Here's more information on that, so you can figure out if that's what she had:


This test is used not only in patients with conditions such as congestive heart failure, but also in sports medicine to assess the conditioning of *athletes*! I really think it would be the perfect test for your daughter because it won't max out before she reaches her peak level of exertion, like other stress tests might (if performed properly, of course). Also, it measures things that the other stress tests don't (note the big breathing tube in the picture on the first link I sent you), which give a MUCH more complete picture of what is going on with regard to fatigue and exercise intolerance. It really is targeted specifically to what your daughter's symptoms are and getting a more complete picture of what may be causing it.

Vanderbilt does not see pediatrics, but with how close she is there's certainly a chance for an exception. It can't hurt to ask. I hope the neurologist appointment goes well for you. Some neurologists do treat NCS and other autonomic disorders, although NCS in particular is one that is more commonly handled by cardiologists because syncope is often seen as electrophysiologist (EP-cardiologist) territory. At worst, maybe you can ask the neurologist for a referral to an EP-cardio if s/he doesn't want to or can't handle it. Patients generally decide which to see based on what knowledgable docs are available in their vicinity, how far they are able to travel for consultations/testing, which body system(s) are most affected in their case, and personal preference. One thing to be aware of is that there are two different styles of TTT: a neuro TTT and a cardiology TTT. The main difference that is obvious is that a neuro TTT is shorter in duration; I would recommend that if they only want her to have one, it be the longer cardiology style one. Typically the duration of the longer one is around 40 minutes, just to give you an idea so you can gauge if they're ordering the test you want or not.

Oh, one thought on neurology. You may have better luck with a neuromuscular specialist than a general neurologist. That's been my experience and, anecdotally, seems to be not uncommon. I'm not sure why, but it's something else to consider. Also, this year at the age of 33, I became a first-time patient at a local (nationally-renowned) children's hospital. In addition to considering Vanderbilt, think about what the closest renowned children's hospitals are to you. (I don't know which direction you're coming from to Vandy, or I might be able to give you a tip or two.) Sometimes pediatricians at big-name children's hospitals can have insight that the adult hospitals are missing. In my case, we're testing for congenital metabolic disorders, something generally in the purview of pediatrics but which can manifest later in life.

Keep me updated and let me know what other information I can help you with. There's no reason this should ruin her college athletic career!


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