Blood clots in the lungs (also known as pulmonary embolism) can cause or contribute to PH in many patients.
In some patients, PH is directly due to pulmonary embolism. These patients are said to have WHO Group IV PH, or chronic thromboembolic PH (CTEPH).
In many other patients with PH, blood clots in the lungs are not the cause of PH. However, even in these patients, PH itself causes damage to the innermost lining cells (also known as endothelial cells) of the pulmonary arteries. Damage to endothelial cells can lead to blood clots forming (also known as thrombosis) in the pulmonary arteries.
This thrombosis in the pulmonary arteries can lead to the worsening of PH over time