PULMONARY HYPERTENSION

Possible Cause

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 blood vessels in your lungs (pulmonary arteries, capillaries and veins) to the left side of your heart.

Ordinarily, the blood flows easily through the vessels in your lungs, so blood pressure is usually much lower in your lungs. With pulmonary hypertension, the rise in blood pressure is caused by changes in the cells that line your pulmonary arteries. These changes cause extra tissue to form, eventually narrowing or completely blocking the blood vessels, making the arteries stiff and narrow. This makes it difficult for the blood to flow, raising the blood pressure in the pulmonary arteries.

Idiopathic pulmonary hypertension

When an underlying cause for high blood pressure in the lungs can't be found, the condition is called idiopathic pulmonary hypertension (IPH). Some people with IPH may have a gene that's a Risk Factors for developing pulmonary hypertension. But in most people with idiopathic pulmonary hypertension, there is no recognized cause of their pulmonary hypertension.

Secondary pulmonary hypertension

Pulmonary hypertension that's caused by another medical problem is called secondary pulmonary hypertension. This type of pulmonary hypertension is more common than is idiopathic pulmonary hypertension. Causes of secondary pulmonary hypertension include:

• Blood clots in the lungs (pulmonary emboli)
• Chronic obstructive pulmonary diseases, such as emphysema
• Connective tissue disorders, such as scleroderma or lupus
• Sleep apnea and other sleep disorders
• Heart abnormalities you're born with (congenital heart defects)
• Sickle cell anemia
• Chronic liver disease (cirrhosis)
• AIDS
• Lung diseases such as pulmonary fibrosis, a condition that causes scarring in the tissue between the lungs' air sacs (interstitium)
• Left-sided heart failure
• Living at altitudes higher than 8,000 feet (2,438 meters)
• Climbing or hiking to altitudes higher than 8,000 feet (2,438 meters) without acclimating first
• Use of certain stimulant drugs, such as cocaine

Eisenmenger syndrome and pulmonary hypertension

Eisenmenger syndrome, a type of congenital heart defect, causes pulmonary hypertension. It is most commonly caused by a large hole in your heart between the two lower heart chambers (ventricles), called a ventricular septal defect (VSD). This hole in your heart causes blood to circulate abnormally in your heart. Oxygen-carrying blood (red blood) mixes with oxygen-poor blood (blue blood). The blood then returns to your lungs instead of going to the rest of your body, increasing the pressure in the pulmonary arteries and causing pulmonary hypertension.

Risk Factors

Although anyone can develop either type of pulmonary hypertension, older adults are more likely to have secondary pulmonary hypertension, and young people are more likely to have idiopathic pulmonary hypertension. Idiopathic pulmonary hypertension is also more common in women than it is in men.

Another Risk Factors for pulmonary hypertension is a family history of the disease. Some genes could be linked to idiopathic pulmonary hypertension. These genes might cause an overgrowth of cells in the small arteries of your lungs, making them narrower.

If one of your family members develops idiopathic pulmonary hypertension and tests positive for a gene mutation that can cause pulmonary hypertension, your doctor or genetic counselor may recommend that you or your family members be tested for the mutation.

Complications

Pulmonary hypertension can lead to a number of complications, including:

• Right-sided heart failure (cor pulmonale) In cor pulmonale, your heart's right ventricle becomes enlarged and has to pump harder than usual to move blood through narrowed or blocked pulmonary arteries. At first, the heart tries to compensate by thickening its walls and expanding the chamber of the right ventricle to increase the amount of blood it can hold. But this thickening and enlarging works only temporarily, and eventually the right ventricle fails from the extra strain.
• Blood clots Clots help stop bleeding after you've been injured. But sometimes clots form where they're not needed. A number of small clots or just a few large ones dislodge from these veins and travel to the lungs, leading to a form of pulmonary hypertension that is reversible with time and treatment. Having pulmonary hypertension makes it more likely you'll develop clots in the small arteries in your lungs, which is dangerous if you already have narrowed or blocked blood vessels.
• Arrhythmia Irregular heartbeats (arrhythmias) from the upper or lower chambers of the heart and these can lead to palpitations, dizziness or fainting and can be fatal.
• Bleeding in the lungs and coughing up blood (hemoptysis) This is another potentially fatal complication.

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