There are five groups of pulmonary hypertension, having different aetiologies:
Group 1: Pulmonary arterial hypertension
Group 2: Pulmonary hypertension related to left heart diseases
Group 3: Pulmonary hypertension related to lung diseases or the shortage of oxygen
Group 4: Pulmonary hypertension related to blood clots in the pulmonary vessels
Group 5: Pulmonary hypertension related to other reasons
Group 1: Pulmonary arterial hypertension
This type of pulmonary hypertension is seen because of structural differences in the distal branches of the pulmonary artery, which carries blood from the right side of the heart to the lungs. In conclusion of these alterations, the radius of the vessel decreases and blood pressure increases. Apart from the possibility of happening because of the genetical inheritance, it can also be seen because of the connective tissue-related diseases, liver problems, congenital heart defects, HIV and some of the medications.
When no reasons can be found for pulmonary arterial hypertension, it’s named “idiopathic”.
Group 2: Pulmonary hypertension related to left heart diseases
When there is a problem with the left side of the heart, the blood can’t flow easily from the lungs to the left side of the heart. Because of that, blood pressure starts to increase in the lungs, and the pressure on the right side of the heart increases indirectly. This group is one of the most commonly seen causes of pulmonary hypertension.
Group 3: Pulmonary hypertension related to lung diseases to shortage of oxygen
The most common reasons in this group:
- Chronic obstructive lung disease
- Interstitial lung disease (Pulmonary fibrosis, as an example)
- Obstructive sleep apnea
The main problem in this group is the decrease in oxygen levels. When the oxygen percentage decreases in the air we inhale, the pulmonary vessels in the lungs start to get narrow. In conclusion, blood pressure increases. In addition, the pulmonary vessels might have been damaged because of other lung diseases.
This group is also among the most commonly seen reasons.
Group 4: Pulmonary hypertension related to blood clots in the pulmonary vessels
It’s a quite rare group of diseases. The blood flow to the lungs decreases because of the blood clots in the vessels, and the pressure inside the pulmonary vessels increases.
Even if these kinds of blood clots can generally be treated with anticoagulants, they may rarely solidify and block the blood flow.
Group 5: Pulmonary hypertension related to other reasons
In this group, there are rare diseases which are gathered under the same title instead of being classified separately.