Primary, or unexplained, pulmonary hypertension (PPH) is a rare lung disorder in which the blood pressure in the pulmonary arteries rises far above normal levels for no apparent reason, resulting in increased work for the heart. It occurs in the absence of other disease in the heart or lungs.
The pulmonary artery is the blood vessel carrying oxygen-poor blood from the right ventricle (one of the pumping chambers of the heart) to the lungs. In the lungs, the blood picks up oxygen and then flows to the left side of the heart, where it is pumped by the left ventricle to the rest of the body through the aorta.
Normal mean pulmonary artery pressure is approximately 14 mmHg at rest. In the PPH patient, the mean blood pressure in the pulmonary artery is greater than 25 mmHg at rest and 30 mmHg during exercise.
This abnormally high blood pressure (pulmonary hypertension) is associated with changes in the small blood vessels in the lungs, resulting in an increased resistance to blood flowing through the vessels. This increased resistance, in turn, places a strain on the right ventricle of the heart, which now has to work harder than usual against the resistance to move adequate amounts of blood from the heart through the lungs back into the left side of the heart.
PPH mostly occurs in young and middle-aged women. Researchers believe that one of the ways PPH starts is with injury to the layer of cells (the endothelial cells) that line the small blood vessels of the lungs. This injury, which occurs for unknown reasons, may bring about changes in the way the endothelial cells interact with smooth muscle cells in the vessel wall. As a result, the smooth muscle contracts more than normal and thereby narrows the vessel.
The process eventually results in the development of extra amounts of tissue in the walls of the pulmonary arteries. The amount of muscle increases in some arteries, and muscle appears in the walls of arteries that normally have no muscle. With time, scarring, or fibrosis, of the arteries takes place, and they become stiff as well as thickened. Some vessels may be completely blocked. There is also a tendency for blood clots to form within the smaller arteries.
In response to the extra demands placed upon it by PPH, the heart muscle gets bigger, and the right ventricle expands in size. Overworked and enlarged, the right ventricle gradually becomes weak and loses its ability to pump enough blood to the lungs.
Symptoms include weakness, fatigue, shortness of breath (dyspnea), dizziness, and fainting spells with exertion. Swelling in the ankles or legs (edema), bluish lips and skin (cyanosis), and chest pain (angina) are other symptoms of the disease.
A complete medical history and physical examination are performed. A chest X-ray, echocardiogram (ultrasound study of the heart), lung scan (to rule out pulmonary embolism - a clot in the lung), and an electrocardiogram (EKG) may be done.
Some patients may be helped by drugs that dilate the blood vessels (vasodilators). The effect of such drugs must first be evaluated during cardiac catheterization, because in some patients they may cause serious problems.
Vasodilators have been shown to improve PPH in some people but they rarely normalize the elevated blood pressure in the lungs completely and must often be used in high doses.
Some people with PPH treated with vasodilators may become worse if the vasodilators lower their "regular" blood pressure more than their pulmonary blood pressure. Chronic infusion of prostacyclin, a potent pulmonary vasodilator, may also improve outcome. Supplemental oxygen may be required.
A blood thinner (warfarin) may be beneficial. Some physicians may also recommend the use of oxygen on a regular continuous basis, because one of the consequences of PPH is a low level of oxygen in the blood.
Heart-lung or single-lung transplantation is another option.
Are there other medical conditions to consider?
Is there evidence of fibrosis or blockage of the blood flow?
What are treatment options?
Do you recommend the use of vasodilators?
What are the risks of vasodilators?
Would oxygen help?