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Yes, in some patients, PH can be due to blood clots in the lungs (also known as pulmonary embolism). After pulmonary embolism, up to 4% of patients may develop PH within 2 years. 
PH due to pulmonary embolism is called chronic thromboembolic PH (CTEPH).

  • The risk of PH after pulmonary embolism is quite small; in most patients with pulmonary embolism, the body is able to break up the clot, leaving no evidence of PH
  • However, PH will develop within 2 years of pulmonary embolism in a small number of patients (up to 4%); the risk is highest in patients with multiple episodes of pulmonary embolism
  • Patients with pulmonary embolism who also develop PH have a higher risk of dying
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 cellscan lead to blood clots forming (also known as thrombosis) in the pulmonary arteries.
  • This thrombosis in the pulmonary arteries narrows the pulmonary arteries
  • This thrombosis in the pulmonary arteries can further increase the blood pressure in the pulmonary arteries (pulmonary artery pressure)

This thrombosis in the pulmonary arteries can lead to the worsening of PH over time

All patients diagnosed with PH should be assessed for the presence of blood clots in the lungs. This is for several reasons:

  • Pulmonary embolism is a common cause of PH
  • Treatment with blood thinners (also known as anti-coagulants) can greatly decrease the risk of recurrent pulmonary embolism