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 (ECG), 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. In people with heart failure, the heart does not pump blood adequately (see also Heart Failure).
Pulmonary hypertension is classified based on the cause because the approach to treatment depends, in part, on the cause. There are many causes of pulmonary hypertension, including
Left-sided heart failure is one of the most common causes of pulmonary hypertension. Left-sided heart failure can occur in people who have longstanding high blood pressure or coronary artery disease. When the left side of the heart cannot pump blood out to the body normally, blood backs up in the lungs and increases blood pressure there.
Lung disorders can also lead to pulmonary hypertension. When the lungs are impaired by a disorder, more effort is needed to pump blood through them. One of the most common conditions is chronic obstructive pulmonary disease (COPD—see Chronic Obstructive Pulmonary Disease (COPD)). Over time, COPD destroys the small air sacs (alveoli) together with their small blood 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. Other conditions that lower blood oxygen levels, such as having sleep apnea, or living in or prolonged visiting in places that are at high altitudes can also cause pulmonary hypertension. Other lung disorders that may cause pulmonary hypertension include pulmonary fibrosis, cystic fibrosis, sarcoidosis, Langerhans cell histiocytosis (granulomatosis), and extensive loss of lung tissue as a result of surgery or injury.
Less common causes include obesity with reduced ability to breathe (pickwickian syndrome), neurologic disorders involving the respiratory muscles, chronic liver disease (usually cirrhosis), and HIV infection. Drugs that can cause pulmonary hypertension include cocaine and amphetamines. In the 1990s, pulmonary hypertension occurred in some people who took the diet drugs dexfenfluramine and phentermine (fen-phen). 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). In the tropics, schistosomiasis, a parasite disorder, is a common cause. Certain bodywide disorders can cause pulmonary hypertension, such as autoimmune disorders (for example, rheumatoid arthritis and related disorders), sickle cell disease, and sarcoidosis.
Inherited genetic mutations can also cause pulmonary hypertension. 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.
Pulmonary hypertension also can occur in newborns (see Persistent Pulmonary Hypertension).
Shortness of breath during 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 during exertion. The person is likely to feel weak because body tissues are not receiving enough oxygen. Other symptoms, such as coughing (rarely, coughing up blood) 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. Rarely, people become hoarse.
Some people with pulmonary hypertension have connective tissue disorders, especially systemic sclerosis (see Systemic Sclerosis).
Based on the symptoms, doctors may suspect pulmonary hypertension, particularly in people who have an underlying lung disorder or other known cause of pulmonary hypertension. Tests are done. 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 (right heart catheterization—see Cardiac Catheterization and Coronary Angiography). Other tests may be done to help determine the cause of pulmonary hypertension and to measure its severity. For example, testing may include high-resolution computed tomography (CT) of the chest (for detailed information about lung disorders), blood tests to identify autoimmune disorders, and CT angiography to look for blood clots in the lungs.
Treatment of pulmonary hypertension is best directed at the cause when the cause has been identified.
Vasodilators (drugs to dilate blood vessels) are often helpful for pulmonary hypertension that occurs in people with idiopathic or inherited pulmonary hypertension, autoimmune disorders, chronic liver disease, HIV infection, and some congenital heart disorders and in people with pulmonary hypertension caused by drugs or toxins. In contrast, vasodilators have not proved effective for people with pulmonary hypertension due to an underlying lung disorder. Vasodilators work by reducing blood pressure in the pulmonary arteries. Vasodilators may improve quality of life, increase survival, and prolong the time until lung transplantation needs to be considered. Before administering vasodilators, however, doctors may 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.
Vasodilators include drugs related to prostacyclin (which dilates the pulmonary artery), such as epoprostenol given intravenously, iloprost or treprostinil given via inhalation, or treprostinil injected under the skin. Vasodilators can also be given by mouth, including phosphodiesterase-5 inhibitors (for example, sildenafil and tadalafil), which are used more commonly to treat erectile dysfunction, endothelin-receptor antagonists (bosentan, ambrisentan, and macitentan), and a guanylate cyclase stimulator (riociguat). Endothelin is a substance in the blood that causes constriction of the blood vessels. Phosphodiesterase inhibitors and the guanylate cyclase stimulator increase the ability of nitric oxide, a substance normally present in the body, to widen (dilate) the pulmonary artery.
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).
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.