Pulmonary hypertension (PH) is a rare disease characterized by abnormally high blood pressure in the pulmonary arteries, which are responsible for transporting blood from the heart to the lungs. As a result of blood vessel narrowing, the heart’s right ventricle needs to work harder to pump blood, becoming enlarged and gradually weakened.
Cases of PH are sometimes associated with an underlying disease, which can be a heart or lung condition. It also is believed that genetics play an important role in the development of the disease.
Depending on the cause, PH is classified into five groups, created by the World Health Organization. These groups are as follows:
Group 1: Pulmonary arterial hypertension (PAH)
This group includes pulmonary arterial hypertension or PAH, which can result from one of several causes, or for no apparent reason, in which case it’s called idiopathic.
Some of the causes include other diseases, such as connective tissue disorders — such as scleroderma and lupus — congenital heart disease, chronic liver disease or cirrhosis, and AIDS.
This type of PH has been related to appetite suppressants, which led to their withdrawal from the U.S. market. The use of illegal drugs such as methamphetamines and cocaine also can cause this type of PH.
Among other genes, mutations in the BMPR2 gene also can cause PAH. This gene is an important element for the regulation of numerous cells in the body’s tissues. Mutations in BMPR2 have been associated with the overgrowth of smooth muscle cells in pulmonary vessels, which narrows blood vessels and increases resistance to blood flow.
If a mutation passes down from one generation to another, the disease is known as familial or heritable PAH. However, not every person with an altered gene will develop this condition. PAH is typically inherited in an autosomal dominant pattern, which means that a single copy of the disease-associated mutation is enough to cause the disorder.
Group 2: PH caused by left-sided heart disease
Causes of PH in this group include failure of the lower left heart chamber or left ventricle, a condition called left-side heart failure, as well as aortic valve disease — when the valve between the left ventricle and the aorta does not work properly.
Mitral valve disease, in which the function of the valve between the upper left heart chamber or atrium and the left ventricle is impaired is another cause of PH in this group.
Group 3: PH caused by lung disease
PH also may be caused by chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lungs, and pulmonary fibrosis, a disorder in which lung tissue becomes damaged and scarred.
Low oxygen levels — caused by high altitude and sleep apnea, a condition in which breathing frequently stops and starts during sleep — also are risk factors for PH.
Group 4: PH caused by chronic blood clots (chronic thromboembolic PH, CTEPH)
The presence of blood clots in the lung vessels, also known as pulmonary embolism, also is a possible cause for PH in this group. Blood clots block blood flow and lead to increased blood pressure in lung vessels. Anticoagulant drugs usually dissolve such blood clots. However, in rare cases, they fail to dissolve and turn into scars, blocking blood flow.
Group 5: PH induced by other health conditions
This group includes blood disorders, such as sickle cell anemia — an inherited red blood cell disorder — polycythemia vera, and essential thrombocythemia.
Inflammatory conditions such as sarcoidosis and ANCA-associated vasculitis, also are possible causes of PH in group 5.
In this group are also included kidney disease and metabolic disorders, such as Gaucher disease and glycogen storage disease.
The strain on lung vessels caused by certain tumors also may be related to the development of PH.
Eisenmenger Syndrome and PH
Eisenmenger syndrome is a congenital medical condition, which means that a person is born with the disorder. Most commonly, this syndrome is the result of a hole between the two ventricles, known as a ventricular septal defect.
Normally, the oxygen-rich and oxygen-poor types of blood circulate separately. However, in people with Eisenmenger syndrome, the oxygen-poor blood crosses the hole in the heart or blood vessels, causing the two blood types to mix.
Regardless of the specific heart defect, this disorder increases the pressure in the pulmonary artery and, over time, damages the smaller blood vessels in the lungs.
Last updated: June 16, 2021
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