Pulmonary hypertension begins when tiny arteries in your lungs become narrow or blocked. This causes increased resistance to blood flow in your lungs, which in turn raises pressure within the pulmonary arteries. As the pressure builds, your heart's right ventricle must work harder to pump blood through your lungs, eventually causing the heart muscle to weaken and sometimes to fail completely.

High blood pressure (hypertension), is a condition in which blood travels through the body's arteries at a pressure too high for good health. A far less common type of high blood pressure affects only the arteries in the lungs. Known as pulmonary hypertension, it's a serious illness that becomes progressively worse and may eventually prove fatal.

No cure for primary pulmonary hypertension currently exists, but drug treatments can help lessen symptoms and improve quality of life for many people with the condition.

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Signs and symptoms

The signs and symptoms of pulmonary hypertension are subtle in the early stages of the disease and may not be apparent for months or even years. As the disease progresses, signs and symptoms become more noticeable. They include:

• Shortness of breath (dyspnea). Initially, you may notice that you're short of breath only when you exert yourself physically, but eventually you may be short of breath most of the time.

• Fatigue.

• Dizziness or fainting spells (syncope).

• Chest pressure or pain.

• Swelling (edema) in your ankles, legs and eventually in your abdomen.

• Bluish color to your lips and skin (cyanosis).

• Racing pulse or increased heart rate.

Causes

Your heart has two upper and two lower chambers. Each time blood passes through your heart, the lower-right chamber (right ventricle) pumps blood to your lungs through a large blood vessel (pulmonary artery). In your lungs, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then flows through the pulmonary veins to the left side of your heart. From there, it's pumped by the left ventricle to the rest of your body through another large blood vessel, the aorta.

The heart has two upper chambers (the right and left atria) and two lower chambers (the right and left ventricles)....When the tiny arteries in your lungs become narrow or blocked, there's increased resistance to blood flow through the lungs. This in turn causes increased blood pressure within these arteries — ...

Ordinarily, the blood vessels in your lungs provide less resistance to blood flow than the blood vessels in the rest of your body do. For this reason, blood pressure is usually much lower in the vessels in your lungs. Normal systolic pressure in your lungs is about 14 millimeters of mercury (mm Hg) when you're at rest. Pulmonary hypertension is defined as systolic lung blood pressure greater than 25 mm Hg at rest and 30 mm Hg during exercise.

The overall rise in blood pressure in pulmonary hypertension is the end result of a process that begins with changes in the endothelial cells that line the lungs' arteries. These changes cause the formation of extra tissue that eventually narrows or completely blocks the blood vessels. Scarring (fibrosis) usually also occurs, making the arteries stiff as well as narrow. This creates increased resistance to blood flow, which raises pressure in the pulmonary arteries.

Primary pulmonary hypertension
When an underlying cause for the high blood pressure in the lungs can't be found, the condition is called primary pulmonary hypertension (PPH). But although the exact cause of PPH isn't known, scientists believe that most people who develop the disorder are especially sensitive to substances that cause the blood vessels to constrict. Cocaine and the diet drug fenfluramine (fen-phen), which was withdrawn from the market in 1997, are two of the substances that may contribute to PPH in some people.

• Cirrhosis

• Emphysema

• Heart failure

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• Lupus

• Sleep apnea

In addition, a small percentage of people with PPH have an inherited predisposition for the disease. In these people, other medical conditions appear to trigger pulmonary hypertension. These conditions include chronic liver disease (cirrhosis), AIDS, sickle cell anemia and connective tissue diseases such as scleroderma and lupus.

Secondary pulmonary hypertension
When pulmonary hypertension is the result of another condition, it's called secondary pulmonary hypertension. The secondary form is the most common type of pulmonary hypertension. Medical conditions that may lead to secondary pulmonary hypertension include:

• Blood clots in the lungs (pulmonary emboli).

• Chronic obstructive pulmonary diseases, such as emphysema.

• Connective tissue disorders, such as scleroderma.

• Sleep apnea.

• Congenital heart disease.

• Lung diseases such as pulmonary fibrosis — a condition that causes scarring in the tissue between the lungs' air sacs (interstitium). In this case, pulmonary hypertension may occur when the lungs' smallest arteries and capillaries are compressed and obliterated by scar tissue.

• Left heart failure. When you heart's left ventricle weakens and can't pump out enough blood, the increase in pressure backs up through the pulmonary veins to the arteries in your lungs.