Pulmonary hypertension is a condition in which blood pressure in the arteries of the lungs (the pulmonary arteries) is abnormally high.

• Many disorders can cause pulmonary hypertension.
• People usually have shortness of breath upon exertion and loss of energy, and some people feel light-headed or fatigued on exertion.
• Chest x-rays, electrocardiography, and echocardiography give clues to the diagnosis, but measurement of blood pressure in the right ventricle and the pulmonary artery is needed for confirmation.
• Treatment of the cause and use of drugs that improve blood flow through the lungs are helpful.

Blood travels from the right side of the heart through the pulmonary arteries into the lungs. There, carbon dioxide is removed from the blood and oxygen is added. Normally, the pressure in the pulmonary arteries is low, allowing the right side of the heart to be less muscular than the left side (because relatively little muscle and effort are needed to push the blood through the lungs via the pulmonary arteries). In contrast, the left side of the heart is more muscular because it has to push blood through the entire body against a much higher pressure.

If the pressure of the blood in the pulmonary arteries increases to a sufficiently high level, the condition is called pulmonary hypertension. With pulmonary hypertension, the right side of the heart must work harder to push the blood through the pulmonary arteries into the lungs. Over time, the right ventricle becomes thickened and enlarged and heart failure develops (see Heart Failure).

Cor Pulmonale: A Disorder Stemming From Pulmonary Hypertension
Cor pulmonale is pulmonary hypertension related to the underlying lung disorder. The right ventricle of the heart becomes enlarged and thickened, eventually resulting in heart failure. Cor pulmonale develops because the pulmonary arteries constrict and become thickened in response to low oxygen levels. This thickening narrows the passageway through which blood flows through the lung, and this narrowing, in turn, increases the pressure in the pulmonary arteries. Once pulmonary hypertension develops, the right side of the heart has to work harder to compensate, but the increased effort causes it to become enlarged and thickened. These changes can lead to right-sided heart failure. The failing right ventricle places a person at risk of pulmonary embolism because blood flow is abnormally low, so blood tends to pool in the legs. If clots form in the pooled blood, they may eventually travel to and lodge in the lungs, with dangerous consequences. There may be few symptoms of cor pulmonale until the disorder is quite advanced. When symptoms do occur, people describe shortness of breath during exertion, light-headedness, fatigue, and chest pain. Symptoms of heart failure, such as swelling (edema) in the legs and progressively worse shortness of breath, also develop. A number of tests are available to help doctors diagnose cor pulmonale, but the diagnosis is often suspected on the basis of the physical examination. By listening through a stethoscope, doctors can hear certain characteristic heart sounds that occur when the right ventricle becomes strained. Chest x-rays can show the enlarged right ventricle and pulmonary arteries. Doctors evaluate the function of the left and right ventricles with echocardiography, radionuclide studies, and cardiac catheterization. Treatment is usually directed at the underlying lung disorder. Measures to relieve right-sided heart failure are also taken. Because people with cor pulmonale are at increased risk of pulmonary embolism, doctors may prescribe an anticoagulant to be taken long-term.

Causes

There are many causes of pulmonary hypertension, including HIV infection, drugs and toxins, lung disorders, and low blood oxygen levels (hypoxia). One of the most common causes of pulmonary hypertension is left-sided heart failure, which can occur if

• One of the heart valves does not work properly
• The left ventricle is stressed by high blood pressure
• A heart attack or some other disorder involving the heart diminishes the ability of heart muscle to pump

Lung disorders can also lead to pulmonary hypertension. One of the most common conditions is chronic obstructive pulmonary disease (COPD–—see Chronic Obstructive Pulmonary Disease (COPD)). When the lungs are impaired by a disorder, more effort is needed to pump blood through them. Over time, COPD destroys the small air sacs (alveoli) together with their small vessels (capillaries) in the lungs. The single most important cause of pulmonary hypertension in COPD is the narrowing (constriction) of the pulmonary arteries that occurs as a result of low blood oxygen levels. Having sleep apnea and living in or prolonged visiting in places that are at high altitudes can also cause pulmonary hypertension by lowering levels of oxygen in the blood. Other lung disorders that may cause pulmonary hypertension include pulmonary fibrosis, cystic fibrosis, sarcoidosis, and Langerhans' cell granulomatosis (histiocytosis).

Less often, pulmonary hypertension is caused by extensive loss of lung tissue from surgery or trauma. Other causes include heart failure, scleroderma, obesity with reduced ability to breathe (pickwickian syndrome), neurologic diseases involving the respiratory muscles, chronic liver disease, and HIV infection. Pulmonary hypertension also occurred in some people who took the diet drugs dexfenfluramine and phentermineSome Trade Names
ADIPEX-P
(fen-phen) during the 1990s. A cause of sudden pulmonary hypertension is pulmonary embolism, a condition in which blood clots become lodged in the arteries of the lung (see Pulmonary Embolism (PE)). In the tropics, schistosomiasis, a parasite disorder, is a common cause.

A small group of people have pulmonary hypertension without any identifiable cause (called idiopathic pulmonary hypertension). Women are affected by idiopathic pulmonary hypertension twice as often as men, and the average age at which the diagnosis is made is about 35 years.

Symptoms

Shortness of breath upon exertion is the most common symptom of pulmonary hypertension, and virtually everyone who has the condition develops it. Some people feel light-headed or fatigued on exertion. The person is likely to feel weak because body tissues are not receiving enough oxygen. Other symptoms, such as coughing and wheezing, are usually caused by the underlying lung disorder. Swelling (edema), particularly of the legs, may occur because fluid may leak out of the blood vessels and into the tissues. Swelling is usually a sign that right-sided heart failure has developed.

Some people with pulmonary hypertension have connective tissue disorders, especially systemic sclerosis (scleroderma–—see Autoimmune Disorders of Connective Tissue: Systemic Sclerosis (Scleroderma)).

Diagnosis

Based on the symptoms, doctors may suspect pulmonary hypertension in people who have an underlying lung disorder. A chest x-ray may show that the pulmonary arteries are enlarged. Electrocardiography (ECG) and echocardiography enable doctors to look for certain problems with the right side of the heart before cor pulmonale develops. For example, thickening of the right ventricle or a partial reversal (back flow) of blood through the tricuspid valve between the right atrium and right ventricle may be detected on an echocardiogram. Pulmonary function tests help doctors assess the extent of lung damage. A sample of blood may be taken from an artery in an arm to measure the level of oxygen in the blood.

A definite diagnosis of pulmonary hypertension usually requires passing a tube through a vein in an arm or a leg into the right side of the heart to measure the blood pressure in the right ventricle and the pulmonary artery.

Treatment

Treatment of pulmonary hypertension is best directed at the cause when the cause has been identified. Vasodilators (drugs to dilate blood vessels), such as calcium channel blockers and prostacyclin analogs, are often helpful for pulmonary hypertension that occurs in people with scleroderma, chronic liver disease, and HIV infection. In contrast, these drugs have not proved effective for people with pulmonary hypertension due to an underlying lung disorder. For most people with idiopathic pulmonary hypertension, vasodilators, such as prostacyclin, drastically reduce blood pressure in the pulmonary arteries. Prostacyclin given intravenously through a catheter that is surgically implanted in the skin improves the quality of life, increases survival, and prolongs the time until lung transplantation needs to be considered. Before administering vasodilators, however, doctors usually first test the effectiveness of these drugs while the person is in a cardiac catheterization laboratory, because their use may be dangerous in some people. Subcutaneous (under the skin) and inhaled forms of prostacyclin are now available and are effective in some people.

Endothelin (a substance in the blood that causes constriction of the vessels) receptor blockers, bosentanSome Trade Names
TRACLEER
and ambrisentanSome Trade Names
LETAIRIS
, given by mouth, have been effective in some people with mild disease. A drug similar to prostacyclin, called iloprostSome Trade Names
VENTAVIS
, can be administered by inhalation and, as a result, has a much lower risk of complications than prostacyclin. Oral sildenafilSome Trade Names
VIAGRA
is very effective in some people with pulmonary arterial hypertension.

In people with pulmonary hypertension who have a low level of oxygen in the blood, the continuous use of oxygen through nasal prongs or an oxygen mask may reduce blood pressure in the pulmonary arteries and may relieve shortness of breath. A diuretic drug is usually given to assist the right ventricle in maintaining a normal volume for effective beating and to reduce leg swelling. An anticoagulant may also be given to reduce the risk of blood clots and subsequent pulmonary embolism (see Pulmonary Embolism (PE): Pulmonary Embolism).

Lung transplantation is an established procedure for treating people with pulmonary hypertension. Lung transplantation can be used only in people with severe disease who are healthy enough to withstand the potential consequences and difficulties with the procedure.

Last full review/revision March 2008 by John H. Newman, MD