POTS: Why It's Not About Your Heart Rate

It is slightly too long for a podcast episode description. The content is good, but I’d tighten it so someone can understand the episode quickly without feeling like they have already consumed it.

If your heart races every time you stand—but your cardiac testing keeps coming back normal—the heart may not be the real problem.

POTS is diagnosed by changes in heart rate, but research suggests that the heart-rate increase may be a response to something happening earlier: an excessive drop in cerebral blood flow when you become upright.

In this episode, Dr. Spencer Zimmerman explains why this matters, how the brain and autonomic nervous system normally regulate blood flow, and how impaired regulation may contribute to dizziness, brain fog, fatigue, shortness of breath, digestive problems, temperature intolerance, and other symptoms.

You’ll also learn why salt, electrolytes, compression, and medications may help without fully explaining—or addressing—why you remain stuck.

If you have POTS or dysautonomia and feel like no one has connected all your symptoms, this episode will help the bigger picture make more sense.

Transcript

If your heart races every time you stand up, but every single heart test you get is normal, this video is for you.By the end of this video, you should have an understanding of why, even though POTS is diagnosed based upon changes in your heart rate when you make positional changes, the heart itself may not actually be the problem.If you have POTS or any other type of dysautonomia, or you think you may have it, one of the most common referrals you are going to get is going to be to a cardiologist.And here's what that journey is going to look like.You're gonna be sent to a cardiologist.They may or may not do tilt tables.Not all of them do.They may do orthostatic testing, where you will lay down, they're gonna get a baseline heart rate and blood pressure, and then they're gonna stand you up, and then they're gonna check your heart rate and blood pressure every one to 2 minutes, looking for hallmark changes in heart rate without a significant drop in blood pressure.Now, what is that increase in heart rate going to look like?If you're an adult, we're looking for greater than 30 beats per minute.And if you're a teenager, it's gonna be greater than 40, without a significant drop in blood pressure.That is characterized by a drop of greater than 20 for the top number, so your systolic, or ten for the lower number, which is your diastolic.If you do a tilt table, they will do this, but they'll also often give you something known as nitroglycerin.This is much more provocative and acts as a little bit of a shock to the system to say, "Can everything function in the way it needs to?"A lot of providers don't do this, so whether or not you get this is gonna depend very much from the provider you go to.After this, they may do an echo.An echo is a type of evaluation ultrasound where they're gonna look at the structure of your heart.They wanna say, "Are your valves okay?Is there anything else in your structure?"And lastly, what happens with how well your heart's pumping blood?They're looking at your ejection fractions, is this appropriate or not?Because if they find stuff in this evaluation, then you don't actually have POTS.You have a cardiovascular reason for why you are feeling.But for most of you, all of these tests are going to come back normal except for the orthostatic testing that is done.And this leaves a lot of frustration because you're like, "But why am I feeling so bad?"This is where we really need to look at the research and get an understanding first of what happens when you make a positional change, because if you understand this, you will then understand what happens in POTS and why you feel bad as a result.This is a graphicThis is a graphic that looks at what happens in a healthy individual, and then we'll dissect what happens in the world of POTS.So when you are laying down, all your blood volume is pretty equally distributed, and then you're gonna stand up.Now, a variety of things are gonna happen pretty instantaneously when you make this positional change.You're gonna stand up.As a result of gravity, you're gonna get more blood going to your lower extremities and even your abdomen.So you're gonna get venous pooling.Blood may leave circulation just very briefly.As a result of more blood being down here, you're gonna have less blood in the brain, so decreased cerebral blood volume.And because you have less blood making it back to your heart, each time your heart pumps, you're not getting out as much.And because you're not getting out, out as much, the blood volume, so your cardiac output, will go down.But our system is meant to compensate and regulate for this occurring.This is where we have the baroreceptor response.So you have baroreceptors in your arteries that sense pressure.When pressure goes down, that's less input making its way from the artery to your brain.Your brain senses it, and it says, "Hey, I need you to vasoconstrict, constrict those blood vessels.I also need you to increase the heart rate a little bit to help deal with this," so the brain gets the blood flow and oxygen that it needs, so it is happy and healthy.Now, there's one other reflex that they don't talk about in here, and this is the vestibular sympathetic reflex as well.This also plays a role in making sure the brain gets the blood flow and oxygenation that it needs.ButOh, man.What actually should happen when you make a positional change, and you go from laying to standing?If we can understand this in healthy individuals, we can now understand what's gonna happen in the world of POTS.So first, when you make this positional change, gravity plays an important role.You're gonna get more blood down here in your lower extremities and maybe even here in your abdomen.And when you have less here, what happens?You get less blood to anywhere north of that.This includes returning back to the heart, and most importantly, it's about what gets to the brain.So your cerebral blood volume goes down.We also said less blood gets back to your heart.Now, if you have less blood getting back to your heart, this means every time your heart pumps, you're not getting as much in each squeeze.And when you're not getting as much- You will have reduced blood flow leaving the heart, less blood truly in circulation because you have the pooling.And as a result, your system should recognize this really, really fast.Okay?And then you have what's called a baroreceptor response or a baroreflex.What happens here is your arteries have baroreceptors.Now, it's supposed to sense pressure, so it's constantly sending information to the brain, specifically your brain stem, and says, "Okay, you know what?We've got lots of pressure.We're good, we're good, we're good."When the brain senses that pressure going down, it then fires down and it says, "Okay, we got to do a couple things.We need to constrict the blood vessels so we get more blood going up.We also are gonna increase the heart rate, and everything is happy and healthy."One other thing that's important to understand is going to be your vestibular sympathetic reflex.This also responds, and it does it via the vestibular system.And it fires to the brain stem to also help with vasoconstriction and skeletal muscle pump activation.So this is the mechanism that allows someone to make a positional change and do okay.But unfortunately, this is not what's happening in the world of POTS and other types of dysautonomia.So you don't get just a small increase in heart rate, which is normal.You get an exaggerated increase in heart rate of greater than 30 beats per minute.So what's actually happening here in this arena?'Cause we know the heart rate goes up, but is that the entire story?When we look at this part, they talk about the importance of cerebral blood flow regulation.So your brain uses about 20 percent of the body's oxygen because the brain needs oxygen to be happy and healthy, even though your brain weighs less than 2 percent of the body's weight.Also, the brain produces and uses an enormous amount of energy.So it's very dependent on getting the oxygen and the glucose it needs.And unfortunately, oxygen delivery to the brain must be maintained through cerebral blood flow.That's the only way to make sure it gets the demand that it really needs.If not, issues are going to occur.So when we scroll down here and they're looking at the research, okay?They're looking at changes in cerebral blood flow in orthostatic hypotension or intolerance.They're looking at it in blood flow and POTS.Let's look at some of the parts that we've highlighted.Cerebral blood flow volume was considerably lower in POTS and either normal or transiently increased in those with superventricular tachycardia.So superventricular tachycardia is a cardiovascular issue that causes heart rate to go crazy.So you can have POTS where your heart rate goes crazy with positional changes and have reduced cerebral blood flow, so the amount of blood volume in your brain.But when it's not POTS, even with the tachycardia, guess what?That blood volume actually stays good.What else do we know?In POTS patients, they had twice the drop in cerebral blood volume on a head-up tilt test compared to controls, even when blood pressure remains stable.So people are like, "Well, what if it's because of blood pressure dropping too much?"Couldn't be, but even with a normal blood pressure, this is still occurring, and it's twice as much.And remember, the brain is very, very sensitive to these changes.What else did they notice?Cerebral blood volume oscillated more in POTS compared to healthy controls.Right?So the brain is really struggling to regulate the amount of blood volume that gets there.As a result, drops in cerebral blood volume with head-up tilt tests in POTS occurs beorth- before orthostatic tachycardia and hyperpnea, okay.Um, so this last word, this is faster breathing rates.Now, this part is absolutely essential to understand.There is a change in blood volume in the brain before your heart rate goes crazy.And this is why so many of the experts, and this is where we really need a big shift in this arena, it's your issues are related to the drop in blood volume.That is what matters most.It's not the heart rate that gets all the attention, and this is why we're bringing in far-near infrared spectroscopy, which measures blood oxygenation patterns in the brain.There's other clinics that are doing transcranial Doppler ultrasounds because according to this research study, this is where the attention needs to be.And then we've already said it, right?Cerebral blood volume drops before the rise in heart rate and changes in carbon dioxide in POTS.They've also found that reduced stroke volume and cerebral blood volume drive postural hyperventilation.So a lot of people are like, "Oh, I've got shortness of breath.What's happening?"So when you have shortness of breath, I want you to think, "My brain is not getting enough blood flow and oxygen," not a, "I'm having a panic attack."You can have a panic attack as a result of this.And here's something else.Regardless of the POTS subtype, so you have hyperadrenergic POTS, which is not only an increase in heart rate, but also an increase in blood pressure and catecholamine release.You can have neuropathic, which may be due to small fiber neuropathies in others, hypovolemic, not having enough blood volume, okay?An excessive decrease in orthostatic cerebral blood volume is a consistent mechanism.So this is like the one mechanism that overrides everything else.So I hope you're understanding why this is so important and why your heart rate is doing what it is doing.But we also know that with POTS, POTS is not just purely a manifestation of tachycardia.It manifests as a multi-system and multi-symptom issue.When we look at this research article, Narrative Review of POTS, published a couple years ago, 20 23, they list different systems that are impacted.We have cardiovascular, we have respiratory, we have gastrointestinal, we have urinary, we have musculoskeletal, neurological.You can have hormonal, endocrine, and you can even have mental health issues, psychiatric, as a result of this.And this is where there's so much frustration because you're trying to see, "Okay, I've got shortness of breath.I need to see a pulmonologist.Oh, I've got all these GI issues.Let's see a gastroenterologist.I've got musculoskeletal.Let's do a physical therapist or a chiropractor.Got hormonal stuff.Let's go in and see my OBGYN.Let's see an endocrinologist," right?And you get passed amongst all these ologists, and many of you ultimately leave so much more frustrated than you walked in because no one knows what to do.They keep telling you, "Hey, we're not finding anything."And there's all this confusion about what needs to be going on because you know you have multiple issues, but you're not sure where it all ties in.And this is what brings us to the autonomic nervous system.Encourage everyone, come back here, find this, and just sit on this part of this video and really regurgitate it, and you can also come to this place and read it as well.Remember, your nervous system is broken down into 2 components from an autonomic perspective.That's gonna be your sympathetic and your parasympathetic.When your brain is not getting as much blood flow and oxygenation it needs, it is going to shift into a sympathetic state.That is how it survives, and so you get an imbalance.Now, if you get an imbalance, we need to understand what are all the functions of the autonomic nervous system.This is blood pressure, heart rate, breathing, temperature regulation.A lot of you feel hot, you feel cold.You don't do well when temperature swings.Some of you hate hot weather.Some of you hate cold weather.You can get digestive functionality as a result of the autonomic nervous system.Metabolism, electrolyte balance.How many of you have been told you need just more electrolytes?This plays a role here.Production of body fluids, saliva, sweat, tears.How many of you have dry eyes, dry mouth?You don't sweat as much, and maybe you've been told you have an autonomic neuropathy.Maybe you think you have Sjogren's, but when you do all the testing, it doesn't come back as normal.For some of you, you have an autoimmune disease that they're not catching, but for others of you, this really is a manifestation of autonomic nervous system dysfunction.Urination, bowels, even sexual changes.And then as we see here, it looks at sympathetic versus parasympathetic and all the functions.You can have pupillary changes, saliva, breathing issues, right?All of this stuff plays a really big role.And this is why you have so many symptoms with it.And it's why when people are getting the right treatment, they get a massive improvement throughout the entire body.And this is also why there's so much frustration because people are trying to say like, what are all the things I need to treat versus what are the most important things to treat?And this is where treatment really has to catch up because when we look at this review published in 2026, okay, a state-of-the-art review, and it's not a bad review, to be honest.You know, they look at tilt table testing.Here's how you do it.They go through management, but the management is primarily focused on some very minimal lifestyle stuff.Drink water, have salt, electrolytes, wear compression stockings and wear, avoid triggers.And then here's the pharmacological, right?And we see all of these.Heart rate.So many people are getting stuff to manage their heart rate.But what did we say was the issue based upon the other research?Is it a heart rate issue or is it a blood flow getting to the brain issue?Now, to be fair, there are some of you who do function better with the electrolytes and everything else.You also function better with midodrine.Other people spell it midodrine.Don't care.That's a vasoconstrictor, right, to make sure blood's getting there.Some of you are doing volume expanders, desmopressin, fludrocortisone.Others are doing medications down here for those that have hyperadrenergic POTS.But at the end of the day, when I talk to so many individuals, even these help to varying degrees.Some of you love it.Most of you don't see good results with it.And you'd honestly, most of you are telling me the lifestyle changes just with like salt and electrolytes does the best for you predictably, but it doesn't help you get your life back.And this is where in future videos, we need to go beyond the symptoms.So we've covered the symptoms.We've covered what happens and why things are occurring.We need to understand though, what are the things that coexist with POTS and other types of dysautonomia?Because there's a lot.We also need to understand what are the triggers, okay?Because there's a lot of different triggers that can make you feel worse.And then we've also got to dissect some of these things that are co-occurring in this arena as well, right?What's happening from a mast cell histamine related issue?What's happening with Ehlers-Danlos?What about the overlap with chronic fatigue syndrome, otherwise known as myalgic encephalomyelitis?How does brain injuries play a role in this?And there's so much more.I hope though, after watching this, you now have a much better understanding of what's happening in POTS and why heart rate alone is very misleading and it's the effect of the issue and not the issue itself.And how, if you can better understand what the actual issue is, you understand how it impacts a wide variety of systems throughout the body.And then all of this, when we start tying it in together, actually gives people long lasting solutions and not the forever band-aids that many people believe is what their only solution is.Until next time, I'm Dr. Zimmerman.I'm a dual licensed nurse practitioner and doctor of chiropractic.I've got a clinic, Peak Brain and Body, located near Tampa, Florida.And if you haven't, please subscribe, share this with others.And I hope you enjoyed.I hope you enjoyed this and found a lot of value from it.