CTEPH: A Cardiologist's Guide to Chronic Thromboembolic Pulmonary Hypertension

Most blood clots in the lungs dissolve. You get a pulmonary embolism, you go on a blood thinner, and over the following weeks your body breaks the clot down and clears it out. That's the usual story, and it's a good one. CTEPH is what happens when that clearing doesn't finish. A piece of the clot stays behind, hardens into scar tissue, and permanently narrows the lung arteries. This is the explanation I give patients who've been told they have CTEPH, or who are still short of breath months after a clot and want to understand why.

What CTEPH actually is

CTEPH stands for chronic thromboembolic pulmonary hypertension. Let me take that apart, because the name tells you the whole story. "Thromboembolic" means it starts with a blood clot. "Chronic" means the clot has been there a long time and has stopped behaving like a fresh clot. "Pulmonary hypertension" means high blood pressure in the arteries of the lungs, which are separate from the arteries that carry the blood pressure a cuff measures on your arm.

Here's the sequence. After a pulmonary embolism, the clot is supposed to break down and disappear. In CTEPH, part of it doesn't. Instead it organizes, which is the word we use for a clot turning into tough, fibrous, scar-like material that gets built into the wall of the artery. That scarred tissue narrows the vessel and stays put. Blood thinners can't dissolve it, because it isn't really a clot anymore. It's a permanent obstruction.

CTEPH is uncommon after a pulmonary embolism, showing up in roughly 2 to 4 percent of people who've had one. That sounds small, and it is, but pulmonary embolism is common enough that the total number of people affected is meaningful. Doctors classify CTEPH as Group 4 pulmonary hypertension, its own category, because it has a mechanical cause and, unlike most other kinds of pulmonary hypertension, a potential cure.

Why it strains the heart

To understand why CTEPH makes people sick, it helps to picture the right side of your heart. The right ventricle is a thin-walled pump built for an easy job. It pushes blood a short distance into low-pressure lung arteries. It was never designed to push against high pressure.

When old clots narrow those lung arteries, the pressure inside them climbs, and the right ventricle has to work much harder to force blood through. For a while it manages by thickening and enlarging. Over months and years, though, that strain wears it down, and the right side of the heart begins to fail. That failing right heart is what produces the breathlessness, the fatigue, and eventually the leg swelling. The disease is in the lungs, but the organ that gives out is the heart.

There's a second layer to this that surprised researchers when they found it. CTEPH isn't only about the big clots you can see on a scan. The small vessels of the lung, the ones too tiny to image, develop their own disease over time, a remodeling that raises resistance even in parts of the lung the clots never reached. That's part of why some people still have high pressures after the visible clot is surgically removed, and it's why we think about CTEPH as two problems rolled into one.

Nobody knows for certain why some people's clots refuse to clear. The leading suspects are chronic low-grade inflammation, a clot-dissolving system that doesn't work as well as it should, and underlying differences in how a person's blood clots. It's an area of active research, and for most patients we can't point to a single reason.

What raises the risk

The biggest risk factor is having had a pulmonary embolism, particularly a large one, a recurrent one, or one that struck with no obvious cause. But one of the trickiest things about CTEPH is that up to a quarter of people who develop it have no documented history of a clot at all. Their pulmonary embolism was either silent or missed, and CTEPH is the first sign anything was ever wrong. That's a big reason the diagnosis gets delayed.

A handful of specific conditions make CTEPH more likely. Having your spleen removed raises the risk, as do certain long-term implanted devices such as older pacemaker leads and shunts, and past bloodstream infections tied to indwelling lines. Chronic inflammatory conditions play a role. So do a couple of blood-clotting quirks, including antiphospholipid antibodies, found in about 1 in 10 patients, and persistently high levels of a clotting protein called factor VIII. You don't need any of these to get CTEPH, and having one doesn't mean you'll get it. They just shift the odds.

The symptoms, and why they hide

The main symptom of CTEPH is shortness of breath that slowly gets worse, especially with exertion. Early on you might notice you're winded climbing a flight of stairs you used to take without thinking, or that you can't keep up on a walk. Fatigue is common. As the right heart struggles more, people develop lightheadedness, swelling in the legs and ankles, and sometimes a feeling of pressure or fullness in the belly.

The problem is that every one of those symptoms creeps in gradually and looks like something ordinary. Getting winded on the stairs gets chalked up to age, weight, or being out of shape. Fatigue gets blamed on stress or poor sleep. Because CTEPH develops over months to years rather than striking all at once, and because it's uncommon, the diagnosis is frequently missed for a long time. The single most useful clue, and the one I want people to remember, is breathlessness that persists or worsens in the months after a pulmonary embolism. That is not normal, and it deserves a real workup rather than a shrug about deconditioning.

How we diagnose it

Before we even start looking for CTEPH, one condition has to be met. You need to have been on a full-strength blood thinner for at least three months. That waiting period gives fresh clot the time it needs to dissolve, so that anything still blocking the arteries afterward is the old, organized kind that defines CTEPH. Testing too early can't tell the two apart.

Once that box is checked, the workup follows a clear order.

The best screening test is a ventilation-perfusion scan, usually called a V/Q scan. It uses small amounts of a tracer to compare where air goes in your lungs with where blood flows. In CTEPH, blood flow is blocked in patches that airflow reaches normally, a pattern we call a mismatch. The most useful feature of this test is what a clean result tells us. A normal V/Q scan essentially rules CTEPH out, which is why we reach for it first.

If the scan points toward CTEPH, a CT pulmonary angiogram, a detailed CT scan of the lung arteries with contrast dye, shows the actual changes. In chronic disease these look different from a fresh clot. We see webs and thin bands stretched across the vessels, ring-like narrowings, and arteries that have closed off completely. These findings also help the surgical team judge how reachable the disease is.

The test that confirms the diagnosis for certain is a right heart catheterization. A thin catheter is threaded through a vein into the right side of the heart and the lung arteries to measure the pressures directly. CTEPH requires a mean pulmonary artery pressure above 20 mmHg with a normal downstream wedge pressure, the combination that proves the problem sits in the lung arteries themselves rather than backing up from a weak left heart. Many patients also have a catheter-based pulmonary angiogram, which maps the disease in fine detail so the team can plan the right procedure.

How we treat it

CTEPH treatment is a team sport, and the reason I keep emphasizing expert centers is that the best outcomes come from a group of specialists looking at each case together. There are three main tools, and many patients use more than one over the course of the disease. Everyone with CTEPH stays on a blood thinner for life, no matter which treatments they have, because the underlying tendency to clot doesn't go away.

Surgery to remove the clot

The treatment of choice, and the only one that can cure CTEPH, is an operation called pulmonary thromboendarterectomy, often shortened to PTE or PEA. A surgeon opens the lung arteries and carefully peels out the old, organized clot along with the scarred lining it's grown into. Done at a high-volume center, it's remarkably safe for such a major operation, with a risk of dying around 2 percent, and it produces the biggest gains in symptoms and survival of anything we offer. Every person diagnosed with CTEPH should be evaluated for whether they're a surgical candidate. That assessment comes first, before any other treatment is chosen.

Balloon procedures for deeper disease

Not everyone can have the surgery. More than a third of patients have disease that sits too far out in the smaller branches for a surgeon to reach, or other factors that make an operation too risky. For them, balloon pulmonary angioplasty, or BPA, is a strong option. It works like a heart-artery angioplasty, threading a catheter with a small balloon out to the narrowed vessels and gently widening them, one session at a time over several visits. BPA also helps people who still have high pressures after surgery.

Medication

A medication called riociguat is approved specifically for CTEPH that can't be operated on, or for pressures that stay high after surgery. It relaxes and opens the lung arteries, which lowers the pressure the right heart works against and improves how far patients can walk. It's the drug backed by the strongest trial evidence in this setting. Medication doesn't remove the clot, so it works alongside the procedures rather than replacing the surgical evaluation.

How serious it is

Left untreated, CTEPH is a serious disease, and the strain on the right heart is progressive. That's the honest part. The hopeful part is that CTEPH stands almost alone among the pulmonary hypertension diagnoses in being curable, and modern results are good. With today's combination of surgery, balloon procedures, and medication, more than 90 percent of patients are alive at three years. Even among people who can't have the curative surgery, the balloon and drug options have changed the outlook substantially.

Two numbers are worth knowing so you're not caught off guard. About a quarter of people who have the surgery still have some residual pulmonary hypertension afterward, which is where balloon procedures and riociguat come in. And because the small-vessel disease I mentioned earlier can persist, follow-up at an expert center continues after treatment. CTEPH is manageable and often curable, and it's also a condition you stay connected to your care team about for the long run.

The one thing I most want you to take away

Early referral to a center that specializes in CTEPH is the single biggest factor in doing well. These centers have the surgeons, the interventional teams, and the imaging experience that a condition this uncommon requires, and the difference between an expert program and an occasional operator is real. If you've had a pulmonary embolism and you're still breathless months later, or you have unexplained and worsening breathlessness with no clear cause, ask specifically about CTEPH and about being referred to a specialized center. It's a diagnosis that's easy to miss and very much worth catching.

Common Patient Questions

Is CTEPH the same as having another blood clot?

No. A new pulmonary embolism is a fresh clot that just arrived and can usually be dissolved by your body with the help of blood thinners. CTEPH is old clot that already turned into scar tissue built into the artery wall, which blood thinners can't clear. That difference is exactly why CTEPH needs surgery or balloon procedures rather than more of the same medication.

I had a pulmonary embolism and recovered. Should I be worried about CTEPH?

Most people who have a pulmonary embolism never develop CTEPH. The one thing to watch for is breathlessness that lingers or gets worse in the months after your clot. If your exercise tolerance isn't coming back the way you'd expect, or it's sliding backward, tell your doctor and ask whether CTEPH should be ruled out. Catching it early is what makes the treatment work best.

Can CTEPH really be cured?

For the right candidate, yes. Pulmonary thromboendarterectomy, the operation that removes the old clot, can restore near-normal lung artery pressures and is potentially curative. Whether you're a candidate depends on where the disease sits in the lung arteries, which is why the evaluation at an expert center is so important. Even when a full cure isn't possible, balloon procedures and medication can improve symptoms and survival a great deal.

Will I be on blood thinners forever?

Yes. Everyone with CTEPH stays on lifelong anticoagulation, whether or not they have surgery. The blood thinner won't dissolve the organized scar tissue that's already there, but it protects you against new clots forming on top of the existing disease, which would make things worse.

Why didn't anyone catch this sooner?

CTEPH is genuinely hard to spot. It's uncommon, its main symptom is gradual breathlessness that mimics ordinary things like aging and being out of shape, and up to a quarter of people who have it never had a diagnosed clot to raise suspicion. A delay isn't a sign anyone was careless. It's the nature of the disease. What helps most is knowing the pattern, so that persistent breathlessness after a clot, or unexplained and worsening breathlessness, gets the workup it deserves.

References

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Published on damianrasch.com. The above information was composed by Dr. Damian Rasch, drawing on individual insight and bolstered by digital research and writing assistance. The information is for educational purposes only and does not constitute medical advice.