Abnormally high pressure in the blood vessels supplying the lungs
Blood is normally pumped through the lungs by the heart at a lower pressure than blood is pumped around the rest of the body. In pulmonary hypertension, the pressure of the blood in the arteries supplying the lungs is abnormally high. Consequently, the right side of the heart, which pumps the blood through the lungs, must contract much more vigorously than normal to maintain an adequate flow of blood through the arteries of the lungs. This causes enlargement of the muscle wall on the right side of the heart.
There are various lung and heart conditions that may result in pulmonary hypertension. For example, in chronic obstructive pulmonary disease, resistance to blood flow in the lungs is caused by destruction of lung tissue. In diseases that cause extensive scarring of the tissue in the lungs, such as fibrosing alveolitis, blood vessels in the lungs are destroyed, making blood flow more difficult. Blood clots in the lungs (see Pulmonary embolism) may obstruct the flow of blood and lead to pulmonary hypertension. Narrowing of the mitral valve in the heart prevents blood from leaving the lungs, causing back pressure (see Mitral stenosis) and pulmonary hypertension.
In some forms of congenital heart disease, the heart pumps more blood than is normal into the lungs, and as a result the pressure rises.
Rarely, sleep apnoea leads to pulmonary hypertension. Occasionally, there is no obvious cause for the condition, and it is then known as primary pulmonary hypertension.
Many people who develop pulmonary hypertension already have symptoms of a long-term heart or lung disorder. The additional symptoms associated with pulmonary hypertension may include:
Shortness of breath that tends to become worse on exertion.
As the disease progresses, shortness of breath becomes increasingly severe until it may occur at rest. Eventually, the right side of the heart, which pumps blood through the lungs, may fail, leading to tissue oedema (swelling caused by fluid build-up), especially around the ankles.
If you have an existing long-term heart or lung disorder and your symptoms suddenly become worse, your doctor may suspect that you are developing pulmonary hypertension. He or she may arrange for a chest X-ray to look for enlarged arteries. An echocardiogram (see Echocardiography) and an electrocardiogram (see ECG) may be carried out to look for signs of heart disease, and lung function tests are useful to assess the extent of lung damage. If the diagnosis is still unclear, a procedure called right heart catheterization may be used. This involves passing a tube through a vein in the arm or leg into the right side of the heart to measure blood pressure there.
If you have already developed pulmonary hypertension, treatment will first be directed at the underlying cause if one is found. Your doctor may advise long-term home oxygen therapy if you have low oxygen levels due to a disorder such as chronic obstructive pulmonary disease. Drugs that prevent blood clotting may be prescribed if the blood vessels in the lungs have become blocked by clots. You may also be prescribed drugs to dilate blood vessels in the lungs and lower the pressure in them. If heart failure has developed, you may be given diuretic drugs to reduce excess fluid.
If the underlying cause of pulmonary hypertension is identified and can be treated successfully, it is possible that the condition may improve. However, in most cases, pulmonary hypertension becomes progressively worse.
In primary pulmonary hypertension and cases in which the underlying cause is untreatable, the disorder may progress to chronic heart failure, which may be life threatening. For this reason, if you have pulmonary hypertension, are under the age of 55, and are otherwise in good health, you may be considered for a heart and lung transplant.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.