Tilt Table Test for POTS: Everything You Need to Know

So many of you have heard that in order to be diagnosed with POTS, it means that you have to do a tilt table test that you pass out on, which can be super scary. And this is a really common misconception that I think it's worth tackling.

Number one, we should probably start out with understanding why should we even bother with a tilt test to start with? What's the utility? And then understand like is the way that we kind of read about it on chat groups or Reddit or anything like that — is that accurate to what people will experience?

Why Do a Tilt Table Test?

Tilt table test is really helpful for anybody that has any type of orthostatic intolerance to understand what is happening with the neurocardiac reflexes in the body. It's a core part of diagnosing POTS through tilt testing. So then you can back out and understand what do we need to do about that.

Now what's interesting about that is the test that you would do if you suspect somebody has POTS is different than the test you might do if somebody is suspected to have orthostatic hypotension. And that lies in the crux of why this can be problematic for people.

Misconception #1: You'll Be Up There for 45 Minutes

Number one is that we're going to leave you up there for 45 minutes. And that can be super scary because for most people, the idea of just standing for 45 minutes sounds impossible. So, the fact that you're going to do it and you have to be still and you're hooked up to all this stuff — feels like you're about to enter "I'm going to have an episode" territory, which can be pretty scary.

What is more realistic, especially for people with POTS, is that you don't need 45 minutes of data collection to be able to know what's going on. For most people, you're looking something closer to like a 10-minute tilt test. And for most people, we don't run into many people that can't handle 10. And if you can't, we're able to gather the data and bring you down right away.

Where we're getting into the 45-minute tests are people where we're looking for vasovagal syncope — where the reason that they are presenting is because they are passing out a lot and they're trying to figure out why. And in that case, they're there to basically try to pass out. And that's some of the discrepancy that people have.

Misconception #2: You're Going to Pass Out

The second thing kind of dovetails right into that — people are typically terrified of passing out. We're just trying to see what happens when you're under that orthostatic load and then what happens when we take it away. So, it's usually about a 10-minute test and we're not looking for you to pass out. And honestly, if you're getting to the point where it's uncomfortable, most of the time by then, we already have all the data that we need and we can start to pull people down. So, it's not as scary as it sounds.

For people that do pass out, and these are people that have cerebral hypoperfusion, people that have hypotension or low blood pressure — those folks in that camp do pass out, and that's what we're trying to solve for. But even if they do, you're on a test where you're like kind of laying down but kind of standing at the same time. So you're very supported. And then you also have on this like nice easy strap that it's loose when you're standing there. So as long as you're doing okay, it's loose and just kind of hanging out like a little harness. And then if you do pass out, you just kind of slide a couple inches down the table. We lay you down, we wake you up, welcome you back, and away you go.

So not something to be overly concerned about because the likelihood that it lasts is pretty low. I know it's scary to pass out, but for most people, it's not a big deal — and most people it won't be the first time they've ever passed out on a tilt test.

Misconception #3: They're Going to Use Nitroglycerin

The last piece that freaks people out is the introduction of nitroglycerin. So there are a lot of times where you'll look at like what is a tilt table and they'll talk about, hey, if we want to move this sucker along, what we'll do is we'll just inject this nitroglycerin into the system which has some wild effects on people. It causes your veins to dilate and that blood gets super heavy. Causes your cardiac output to drop and it reduces sympathetic discharge. So, it's really hard to push blood to your head.

They're using this a lot of times in cases where they're trying to get someone to pass out to see what the syncope looks like. But if you're someone that has POTS, this is contraindicated. This is not something that we should be doing. As a matter of fact, Blair Grubb published about this back in the early 2000s — I think it was 2006-ish. You can fact check me on that. But he had published about this. We're trying to find out what is causing that. So, by pushing into it more, we're really not getting an effect.

Now, we see some cases where people were talking about where they did have that experience. They're calling the hospital. They're saying, "We're going to do the nitroglycerin." They're saying, "I don't really want to." But they're saying like, "That's what we need to do a test." This is an important point to really kind of parse out if you're getting in the weeds on this. So, remember, the cardiologist is probably sending you to a separate lab to have the tilt test done. And the tilt test lab — in some cases, they're not going to necessarily be differentiating between, hey, are we looking for someone with tachycardia or are we looking to find someone that's passing out? And that distinction is actually really important.

What a Good Tilt Test Should Actually Measure

When we're doing a tilt test for someone who we suspect has POTS, we go through a lot of history to be able to determine like where are we at just from a historical perspective. Do you pass out? Do you have syncope? Do you have tachycardia? Are you hyperventilating? Like just simple things that we can understand from a history.

But then when we're doing the test, we're going to gather kind of as much information as we can from that test as possible. And the reason is we don't want to do it more than once to be able to figure out what's going on. So, normally in a conventional test, you're going to look at heart rate done with an EKG and you're going to look at blood pressure on a continuous basis, which is really kind of like a very important part.

In addition to that though, one of the things that we run into is that when we're looking at blood pressure, we're looking at blood pressure in the body. But most people when they experience problems with their blood pressure in POTS cases or they're feeling pre-syncopal or symptoms that feel, you know, dizzy, lightheaded, blurry visioned, getting tunnel vision or my hearing is getting muffled or I'm getting ringing in my ears or headaches — these sorts of problems. A lot of times we're looking at blood pressure changes that aren't occurring so much in the body but in the head.

And our ability to be able to detect that from blood pressure just isn't quite sufficient because we can have normal blood pressure but have alterations in the blood pressure in the brain. And that's like a super key point in what we're talking about.

Adding Transcranial Doppler and CO2 Monitoring

So in order to do that well, the way we do that is using transcranial Doppler ultrasound, which allows us to look at the blood flow on either side of the brain so that we can compare them both to each other but then also compare laying down to standing up. There are other ways to look at this, but as far as being able to move people around, at the current state of technology the ultrasound is really the best option.

But in addition to that, we also have to monitor end-tidal carbon dioxide. Now there's ways to look at carbon dioxide in blood which is really really great. That's probably the best way but it's also hard to get a continuous measure of that in the blood in a noninvasive way. So as a proxy, what people will do and what we do is use the end-tidal carbon dioxide — which is measuring the air that you breathe at the end of that breath, how much carbon dioxide is in it — and it's a very good proxy for how much is in the blood.

Why we do that? Because in order to get a calibrated reading on the Doppler ultrasound, we have to compare it to changes in end-tidal carbon dioxide because they both affect the blood vessels in the brain or the blood pressure in the brain differently than they affect the blood pressure in the body. So that's why we do that. When we do that, it helps us to be able to differentiate what is failing first.

When the Standard Test Leaves You Stuck

So as we talk about a lot, some people can get on a tilt test. They'll say like, "I got up there and they said I didn't qualify for POTS or my blood pressure didn't change enough." And then you're just kind of stuck. We don't have anywhere to go. And they may medicate you just based on symptoms or something like that. And I think that the way you combat that is by having more data collected where we're not left out in the cold kind of wondering what's going on.

There are lots of people that we run into that their heart rate doesn't necessarily go up that high and they'll be surprised by it, and their blood pressure is relatively stable. But we may see giant drops in cerebral perfusion or in end-tidal carbon dioxide. Most of you will notice that when you're upright, it may actually change your breathing. And it changes your breathing in lots of different ways. Some people will find that they breathe heavier or faster or harder.

And also, you might notice that you're just trying to calm yourself down. It's a little bit freaky. You're on this test. You've been anticipating it. And you might find that you try to do like a heavy breathing to calm yourself down. But what's cool is we can actually learn from the way that someone just kind of naturally tries to solve this problem because it can teach us how your body is reflexively using oxygen and CO2 as a counter measure to what's going on with your heart rate.

What About Compression Garments and Medications?

Some people are also wondering like you've been on maybe compression garments or certain types of medicines for a long period of time and it's a little bit nerve-wracking to have to come off of them for the test. But most places will suggest that the test is most valid when we get to see just like what your system does on its own. And I think that's generally true. I think it's way easier to understand the exact mechanism of what's going on better if there are no meds on board. If you've got compression garments on, obviously that's going to affect the circulation in some way. So being able to test with them off is useful.

Now, sometimes you can test with those things on as well and then compare them against each other and see what is affecting what. And actually, sometimes you'll find some very interesting things where you may see changes in heart rate that affect blood pressure in a way you don't expect or affect breathing or perfusion in a way that you don't expect. So sometimes it can be helpful to look at both, but that's kind of at the discretion of the doctor and what they're trying to figure out and solve for.

The Tilt Test Is Worth Doing

So I totally get if you're cruising on the internet looking through all the websites where it can be scary to get a tilt test. I totally get that. But I also understand that from my end, having that information is super valuable to really understanding not just the diagnosis, but at another level deeper, what's the mechanism going on underneath it?

So hopefully this helps clear some of the fears up. Maybe it makes it a little bit easier to make the phone call to go in and have the test done, and hopefully that helps you to be able to figure out the next step and start moving forward in the process.

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