Iliac Vein Compression, POTS, and EDS: The Overlap Nobody Explains
If you live with POTS, you have probably noticed that it rarely travels alone. Many people who have it also have pelvic pain, leg swelling, brain fog, a stretchy-joints diagnosis like Ehlers-Danlos syndrome (EDS), and a stack of other symptoms that no single specialist seems to tie together. You may have been told these are just separate problems that happen to occur in the same person.
There is a growing idea in vascular medicine that, for some people, they are not separate at all. A squeezed vein deep in the pelvis may be one thread connecting several of these symptoms. I want to explain that idea in plain terms: what we think is going on, what the evidence actually shows, and, just as importantly, what it does not show.
I was part of a research team that recently published a systematic review on exactly this overlap in the journal Autonomic Neuroscience: Basic and Clinical. So I will share what we found, but I will also be honest about the limits of the science, because there is a lot of overpromising on the internet about these conditions.
First, the three pieces
POTS (postural orthostatic tachycardia syndrome) is a form of orthostatic intolerance (trouble staying comfortable when upright). When someone with POTS stands, their heart rate jumps by at least 30 beats per minute (40 in teens), without a big drop in blood pressure. Standing brings on dizziness, palpitations, brain fog, and fatigue that ease when lying down.
EDS, especially the hypermobile type, is a connective-tissue difference. Connective tissue is the body’s “packing material.” When it is stretchy like a rubber band, joints are loose and bendy. And so are vein walls.
Iliac vein compression (also called May-Thurner syndrome) is when one of the large veins deep in the pelvis (usually the left one) gets pinched between an artery in front and the spine behind. A related squeeze, Nutcracker syndrome, pinches the left kidney vein. You can read more in my post on iliac vein compression.
These three get diagnosed by three different kinds of doctors: a cardiologist or neurologist, a geneticist, and a vascular specialist. That is a big reason the connection between them gets missed.
The idea that links them: blood pooling low in the body
Here is the mechanism, step by step.
When you stand up, gravity pulls blood down toward your legs and pelvis. In a healthy body, the veins squeeze back and push that blood up to the heart. The heart stays full, and blood pressure holds steady.
Now add a problem. If a vein is squeezed (compression) or stretchy and floppy (as in EDS), blood pools low in the body instead of returning smoothly. Less blood gets back to the heart. Doctors call this reduced “preload.” The heart has less to work with.
The body notices, and it panics a little. It fires up the “fight or flight” system to compensate, which spikes the heart rate. That racing heart on standing is the core feature of POTS.
So the theory is: squeezed or floppy veins → blood pools low → less returns to the heart → the body overreacts → POTS-type symptoms. In our review we described this as venous pooling below the diaphragm reducing preload and triggering a compensatory sympathetic surge. It is a tidy, believable chain and, as I will explain, “believable” is not the same as “proven.”
What our review actually found
We searched the major medical databases and pulled together every study we could find that looked at both pelvic venous problems and orthostatic intolerance. Sixteen studies met our bar, covering 964 people. About 93% were women, and the average age was around 31.
A few findings stood out:
- The overlap is real and measurable. In one study, more than two-thirds of POTS patients had significant left iliac vein compression, compared with about 40% of people without POTS. The squeeze shows up more often in POTS than you would expect by chance.
- Fixing the vein often helped the symptoms. Across the studies that treated the vein, usually with a stent, sometimes with embolization or surgery, orthostatic symptoms generally improved. In the cohorts that used a standard questionnaire, orthostatic symptom scores dropped by about half. In a few striking cases, people who clearly met POTS criteria before a stent no longer met them afterward.
- The symptom picture is bigger than the heart. People in these studies did not just have dizziness. They reported brain fog, migraines, fatigue, irritable-bowel symptoms, bladder pain, and more. And many of these eased after venous treatment too. This fits the everyday experience of people with POTS: it is a whole-body problem.
- Connective tissue keeps showing up. In one group treated for pelvic-vein pain, more than half also met criteria for EDS or a related hypermobility disorder. That is the EDS piece of the puzzle appearing again and again.
Now the honest part: what this does NOT prove
This is the section most websites skip, and it is the most important one.
Almost all the evidence is weak by research standards. The studies were small. Most had no comparison group. Everyone got treated, so there was no untreated group to measure against. Outcomes were usually based on how patients said they felt, not on objective retesting. Our team formally rated the risk of bias as high for most of the studies. That does not mean the findings are wrong. It means they are not yet trustworthy enough to build firm rules on.
Feeling better after a stent does not prove the vein caused everything. Pelvic pain, fatigue, and brain fog can come from many directions at once, nervous-system sensitization, deconditioning, the stretchy connective tissue itself, and simple hope and attention (the placebo effect is real and powerful). When someone improves after treatment, the vein may deserve some credit, all of it, or only part of it. Right now, we honestly cannot tell how the credit should be divided.
Most people with POTS do not need a vein procedure. This is critical. A stent is a permanent implant with real risks. The research so far points to a specific subgroup, often women with pelvic pain or one-sided leg swelling alongside their POTS, frequently with hypermobility. Not to POTS in general. Finding a squeezed vein on a scan does not automatically mean it is the cause of your symptoms or that opening it will fix them. Many people have some degree of iliac compression and no symptoms at all.
There are no high-quality trials yet. No study has fairly compared stenting against good non-surgical care for this exact overlap. Until that exists, vein treatment for POTS should be considered carefully, in the right patient, by an experienced team. Not offered as a routine answer.
So what should you take from this?
If you have POTS, and especially if you also have pelvic pain, one leg that swells more than the other, or a hypermobility diagnosis, it is reasonable to ask whether a venous compression syndrome is part of your picture. That question is worth raising with your doctor. It is under-recognized precisely because the symptoms cross so many specialties.
At the same time, be cautious with anyone, a clinic, a forum, an ad, promising that a stent will cure your POTS. The current science does not support that promise. It supports careful evaluation of a specific subgroup, with clear eyes about what is known and what is not.
It may contribute to POTS symptoms in some people, but it is not a proven cause of POTS in general. The theory is that a squeezed pelvic vein lets blood pool low in the body, reducing blood return to the heart and triggering the racing heart rate seen in POTS. Research shows the compression is more common in people with POTS, and that treating it often helps, but the studies are small and cannot yet prove cause and effect.
Ehlers-Danlos syndrome (EDS) makes connective tissue stretchier than usual, and vein walls are made of connective tissue. Floppier veins may pool blood low in the body when a person stands, which can trigger or worsen POTS. This shared mechanism may partly explain why hypermobility, POTS, and pelvic venous problems so often appear in the same person, though the relationship is still being studied.
No. Most people with POTS do not need vein imaging or a procedure. Checking for venous compression is most reasonable in a specific subgroup, often people who also have pelvic pain, one-sided leg swelling, or a hypermobility diagnosis. A squeezed vein on a scan does not automatically mean it is causing your symptoms, since many people have some compression without any problems.
No, a stent should not be thought of as a cure for POTS. In carefully selected patients, opening a squeezed pelvic vein has been linked to major improvement, and a few people no longer met POTS criteria afterward. But the evidence comes from small studies without comparison groups, and no high-quality trial has confirmed it. A stent is a permanent implant with real risks and is only appropriate for specific patients after careful evaluation.
Think a venous compression syndrome might be part of your picture? Start with my post on iliac vein compression, or read about what a pelvic venogram involves. Physicians can find referral information for Ontario physicians here.
This post draws on Imami, Maliha R., Vandilson Dos Santos Galdino, Paula Harvey, Moira Sarah Selke, Meredith Barr, and Andrew D. Brown. “Pelvic venous disorders and orthostatic intolerance: A systematic review of diagnostic associations and treatment outcomes.” Neuroscience. 2026;266:103451, of which I am the senior author.
