Types of Pulmonary Hypertension

The World Health Organization divides pulmonary hypertension (PH) into five groups. These groups are organized based on the cause of the disease.

In all groups, the average pressure in the pulmonary artery is higher than 25 mmHg at rest or 30 mmHg during physical activity. The pressure in a normal pulmonary artery is about 15 mmHg at rest.

(Note that group 1 is called pulmonary arterial hypertension (PAH) and groups 2 through 5 are called pulmonary hypertension. However, together all groups are called pulmonary hypertension.)

Group 1 PAH includes:

• PAH that has no known cause.
• PAH that's inherited (passed from parents to children through the genes).
• PAH that's caused by conditions such as:
  • Congenital heart disease. This is heart disease that's present at birth.
  • HIV infection.
  • The use of certain diet medicines and street drugs (such as cocaine).
  • Thyroid diseases.

Group 2 includes PH with left heart disease. Conditions that affect the left side of the heart, such as mitral valve disease or long-standing high blood pressure, can cause left heart disease and PH.

Group 3 includes PH linked to lung conditions such as COPD (chronic obstructive pulmonary disease) and interstitial (IN-ter-STISH-al) lung disease. Interstitial lung disease refers to a group of lung diseases that cause scarring of the lung tissue. Group 3 also includes PH linked to sleep disorders that cause breathing problems, such as sleep apnea.

Group 4 includes PH due to blood clots in the lungs or blood clotting disorders. This group also includes PH due to sickle cell anemia.

Group 5 includes PH due to various other diseases or conditions. Examples include sarcoidosis, Langerhans cell histiocytosis, and lymphangioleiomyomatosis (LAM). This type of PH also may be due to an object, such as a tumor, pressing on the pulmonary blood vessels.

Sometimes other terms are used to describe the different types of PH. Group 1 PAH that has no known cause may be called primary or idiopathic (id-ee-o-PATH-ick) PAH. When PH occurs with or is caused by another disease or condition, it may be called secondary PH.