Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare form of pulmonary hypertension, a disease associated with abnormally high pressure in the blood vessels of the lungs, caused by the formation of blood clots.
CTEPH can also be referred to as group 4 pulmonary hypertension, the World Health Organization (WHO) classification that defines the type of pulmonary hypertension based on the underlying cause.
Unlike other forms of pulmonary hypertension, CTEPH is potentially curable with surgery if diagnosed early enough.
Causes of CTEPH
CTEPH is caused by blood clots that obstruct the blood vessels of the lungs, or the pulmonary arteries.
Blood clots are a normal response to bleeding and injuries, as they prevent excessive blood loss, but the body can occasionally produce them without an apparent cause. A “thromboembolism” is a blood clot that has traveled from a vein (emboli) and become stuck in the arteries. This triggers the formation of further clots (thrombi) in the same location. Often the clot forms in a deep vein in the legs, and travel to the lungs.
These clots restrict blood flow through the lungs, which causes a localized increase in blood pressure in the pulmonary arteries and a reduction in the level of oxygen transported to the rest of the body. The increase in blood pressure means the heart must work harder to pump blood, which can weaken the heart muscles.
If the condition is left untreated, scar tissue can form due to damage caused by blood clots that are not cleared from the pulmonary arteries. This scar tissue can further narrow the arteries and cause a partial or complete blockage.
Risk factors for CTEPH
CTEPH can occur without any known cause; however, certain factors are known to increase the risk of developing the disease, including:
- Spleen removal
- Chronic inflammatory disorders such as osteomyelitis (an infection in a bone) or inflammatory bowel disease (IBD)
- Thyroid replacement therapy
- Known increased risk of blood clots
- A family history of blood clots linked to inherited genetic factors
- Blood clotting disorders (hypercoagulability)
Women are also more likely to get CTEPH than men.
The symptoms of CTEPH are similar to other types of pulmonary hypertension, the most common being shortness of breath and fatigue, due to a decrease in oxygen being circulated around the body. As a result, patients usually have a low tolerance for exercise.
Other symptoms include:
- Chest discomfort
- Coughing up blood
- Swelling in the legs
Correctly diagnosing CTEPH is essential, as the underlying cause of pulmonary hypertension can have a huge impact on the treatment options available. Initial diagnosis often consists of the same tests used to diagnose pulmonary hypertension, such as echocardiography and right heart catheterization.
A diagnosis of CTEPH is usually reached by ruling out other causes of pulmonary hypertension, and through imaging tests to confirm the presence of blood clots. Normally, multiple tests are carried out for a complete diagnosis.
A ventilation/perfusion (VQ) scan is one of the most common tests to exclude a CTEPH diagnosis. It measures the air and blood circulation by tracking the movement of medical radioactive tracers through the lungs. A VQ scan that shows no abnormalities normally means the patient does not have CTEPH.
The most accurate test to confirm CTEPH is a pulmonary angiography, which typically involves an X-ray of the patient’s chest and the injection of a dye that can be seen using an X-ray. However, it can also be performed using other imaging scans such as computed tomography (CT) or magnetic resonance imaging (MRI). Using these, a medical specialist can observe the blood flow through the pulmonary arteries, confirming whether there are any blockages and their location. These tests can also be used to determine whether the patient has CTEPH that may respond well to surgical treatment.
Most patients diagnosed with CTEPH are treated using a surgical procedure called pulmonary thromboendarterectomy (PTE). If successful, PTE can cure the disease, or dramatically reduce symptoms.
PTE is a type of open-chest surgery that involves the direct removal of the clots and scar tissue from the pulmonary arteries. It aims to remove the blockages in the blood vessels and restore normal circulation through the lungs.
However, not all patients may be eligible for PTE. For example, if the blood clots are in a location not easily accessible by surgery or are caused by the presence of other conditions such as severe lung disease of left heart disease, PTE cannot be performed. In such situations, there are some medications available that can help.
Adempas (riociguat) is an approved medication for CTEPH that promotes the dilation, or opening up of blood vessels. This may improve blood flow through the lungs, increasing oxygen transport to the rest of the body.
Patients who have CTEPH, or CTEPH that has been cured by PTE, may be advised to take anticoagulants, or blood thinners, such as warfarin. These can help prevent more blood clots from forming in the future.
In extreme cases, a patient may be recommended for a lung transplant if they are not responding well to any other treatment.
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