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 blood vessels in your lungs (pulmonary arteries, capillaries and veins) to the left side of your heart.

Ordinarily, the blood flows easily through the vessels in your lungs, so blood pressure is usually much lower in your lungs. With pulmonary hypertension, the rise in blood pressure is caused by changes in the cells that line your pulmonary arteries. These changes cause extra tissue to form, eventually narrowing or completely blocking the blood vessels, making the arteries stiff and narrow. This makes it harder for blood to flow, raising the blood 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).

Some people with IPH may have a gene that's a risk factor for developing pulmonary hypertension. But in most people with idiopathic pulmonary hypertension, there is no recognized cause of their pulmonary hypertension.

Secondary pulmonary hypertension

Pulmonary hypertension that's caused by another medical problem is called secondary pulmonary hypertension. This type of pulmonary hypertension is more common than is idiopathic pulmonary hypertension. Causes of secondary pulmonary hypertension include:

  • Blood clots in the lungs (pulmonary emboli)
  • Chronic obstructive pulmonary diseases, such as emphysema
  • Connective tissue disorders, such as scleroderma or lupus
  • Sleep apnea and other sleep disorders
  • Heart abnormalities you're born with (congenital heart defects)
  • Sickle cell anemia
  • Chronic liver disease (cirrhosis)
  • AIDS
  • Lung diseases such as pulmonary fibrosis, a condition that causes scarring in the tissue between the lungs' air sacs (interstitium)
  • Left-sided heart failure
  • Living at altitudes higher than 8,000 feet (2,438 meters)
  • Climbing or hiking to altitudes higher than 8,000 feet (2,438 meters) without acclimating first
  • Use of certain stimulant drugs, such as cocaine

Eisenmenger syndrome and pulmonary hypertension

Eisenmenger syndrome, a type of congenital heart defect, causes pulmonary hypertension. It is most commonly caused by a large hole in your heart between the two lower heart chambers (ventricles), called a ventricular septal defect (VSD). This hole in your heart causes blood to circulate abnormally in your heart. Oxygen-carrying blood (red blood) mixes with oxygen-poor blood (blue blood). The blood then returns to your lungs instead of going to the rest of your body, increasing the pressure in the pulmonary arteries and causing pulmonary hypertension.

Mar. 27, 2013