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Causes
By Mayo Clinic staff
Your heart has two upper and two lower chambers. Each time blood passes through your heart, the lower right chamber (right ventricle) pumps blood to your lungs through a large blood vessel (pulmonary artery). In your lungs, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then flows through the pulmonary veins to the left side of your heart. From there, it's pumped by the left ventricle to the rest of your body through another large blood vessel, the aorta.
Ordinarily, the blood flows easily through the vessels in your lungs, so your blood pressure is usually much lower in your lungs. With pulmonary hypertension, the rise in blood pressure is the end result of a process that begins with changes in the cells that line your lungs' arteries. These changes cause the formation of extra tissue that eventually narrows or completely blocks the blood vessels. Scarring (fibrosis) usually also occurs, making the arteries stiff and narrow. This makes it harder for blood to flow, raising the pressure in the pulmonary arteries.
Idiopathic pulmonary hypertension
When an underlying cause for high blood pressure in the lungs can't be found, the condition is called idiopathic pulmonary hypertension (IPH) or primary pulmonary hypertension (PPH).
Some people with IPH have an inherited predisposition for the disease, which may be confirmed by a genetic test. But in most people with idiopathic pulmonary hypertension, there is no recognized cause of their pulmonary hypertension.
Secondary pulmonary hypertension
Pulmonary hypertension resulting directly from another medical problem is called secondary pulmonary hypertension. This type of pulmonary hypertension is more common than idiopathic pulmonary hypertension. Medical conditions that may lead to secondary pulmonary hypertension include:
- Blood clots in the lungs (pulmonary emboli)
- Chronic obstructive pulmonary diseases, such as emphysema
- Connective tissue disorders, such as scleroderma
- Sleep apnea
- Congenital heart disease
- Sickle cell anemia
- Chronic liver disease (cirrhosis)
- AIDS
- Lupus
- Lung diseases such as pulmonary fibrosis, a condition that causes scarring in the tissue between the lungs' air sacs (interstitium)
- Left-sided heart failure
If you live above an altitude of 8,000 feet you can develop pulmonary hypertension as a result of low blood oxygen (hypoxemia) or pulmonary edema (a condition in which the air sacs in the lungs fill with fluid instead of air), which constricts the small pulmonary arteries. People who climb to high elevations without first becoming acclimated are especially at risk of developing a temporary form of pulmonary hypertension known as transient reversible pulmonary hypertension.
Although the exact cause of secondary pulmonary hypertension isn't known, it's possible that some who develop the disorder are especially sensitive to substances that cause the blood vessels to constrict. Cocaine and the diet drug fenfluramine, which was withdrawn from the market in 1997, are two of the substances that may contribute to IPH in some people.
