Causes of pulmonary hypertension
There are five main types of pulmonary hypertension:
Type 1: Pulmonary arterial hypertension (PAH)
This type is rare. It’s caused by changes to very small arteries which take blood from the right side of your heart to your lungs. The walls of the arteries get thicker and stiffer. This makes the space for blood to pass through narrower which increases the blood pressure.
It can be genetically inherited. It’s also associated with connective tissue diseases, liver disease, congenital heart defects, HIV and certain drugs
Type 2: Pulmonary hypertension due to left heart disease
If there are problems with the left side of your heart, it can stop blood flowing easily through the lungs. The right side of your heart has to work harder to pump blood through your lungs. This increases the blood pressure in your pulmonary arteries.
This is one of the most common causes of pulmonary hypertension.
Type 3: Pulmonary hypertension due to lung conditions or lack of oxygen
The common causes in this group are:
- chronic obstructive pulmonary disease (COPD)
- interstitial lung disease (such as pulmonary fibrosis)
- obstructive sleep apnoea (OSA)
These conditions reduce the amount of oxygen getting into your lungs. When there’s a low level of oxygen, your pulmonary arteries get narrower. This increases the blood pressure.
This is another very common cause of pulmonary hypertension.
Type 4: Pulmonary hypertension due to blood clots (chronic thromboembolic pulmonary hypertension)
When blood clots are carried into the pulmonary arteries, they can sometimes form scars. The scars block the flow of blood and this increases the blood pressure.
Type 5: Pulmonary hypertension due to a range of causes
This is a mixed group of rare causes. They’re grouped together because their causes are less clear.