What is PAH?

Pulmonary arterial hypertension, or PAH, is a disease of the vessels that carry blood from the heart to the lungs. In PAH, there is a constant state of high blood pressure in the vessels of the lungs. PAH is not common, but it affects people of all ages and ethnic backgrounds. PAH can occur on its own, or it can be related to other causes.

Understanding the Basics of PAH

Knowing how the cardiovascular system works will help you better understand PAH. The cardiovascular system includes your blood vessels and your heart.

The vessels that carry blood from your heart to your lungs are called pulmonary arteries. When they are healthy, these vessels are large and flexible—this means they are very open and elastic, and blood can easily pass from the heart, through the pulmonary arteries, and into the lungs, ultimately moving oxygen out to the rest of the body.

PAH causes changes in the blood vessels and the pulmonary artery

In PAH, there are changes in the body that cause the pulmonary artery walls to become stiff and thick. These thickened walls result in a tightening, or narrowing of the arteries.¹ In the early stages of PAH, there may be small changes to the pulmonary artery, and the patient might not experience symptoms. When PAH has reached an advanced stage, the blood vessels become more narrow and constricted. The middle walls of the artery grow thick and form scar tissue. As the open area in the blood vessels gets smaller, the blood cannot move as easily through the artery.¹ This causes more resistance in the blood vessels. The heart has to work increasingly harder to overcome the resistance. As this cycle continues, less and less blood is able to flow out of the heart into the body, and the symptoms of PAH intensify.

PAH also affects the heart

The role of endothelin in PAH

Endothelin (en-doe-THEE-lin) is a chemical that occurs naturally in the human body and is produced by endothelial cells, which form a thin lining on the inside of the blood vessels. In normal amounts, endothelin is involved in regular blood flow.¹

People with PAH often have levels of endothelin that are higher than normal.^2,3 Researchers believe that too much endothelin can cause blood vessels to tighten.^2,3* These changes can make it more difficult for blood to flow easily through the blood vessels, and this can affect how well the heart works.²

The importance of an accurate diagnosis

PAH is often not diagnosed in a timely manner. Often a diagnosis may be delayed for months or even years. It is a rare disease that starts with symptoms that are easily confused with those of other conditions, such as asthma. Thus, patients may be misdiagnosed and receive inappropriate treatment for their symptoms.

*Statements are based on observations reported from in vitro or animal trials. The clinical significance in humans is unknown.

IMPORTANT SAFETY INFORMATION
Because of the risks associated with Tracleer, this medication may be prescribed by your doctor only through the Tracleer Access Program.

Liver damage: Tracleer can cause serious liver damage, including in rare cases liver failure and, in situations with regular liver testing, unexplained liver cirrhosis. So you must have a blood test to check your liver function before you start Tracleer and each month after that. Call your doctor right away if you have any of these symptoms of liver problems: nausea, vomiting, fever, unusual tiredness, abdominal (stomach area) pain, or yellowing of the skin or the whites of your eyes (jaundice).

Serious birth defects: Tracleer is very likely to cause serious birth defects. It is important not to be or to become pregnant while taking Tracleer or one month after stopping treatment and to have a pregnancy test before you start the drug and each month thereafter. It is very important for you to use reliable forms of birth control while taking Tracleer. Hormonal contraceptives should not be used alone because they may not be effective in patients taking Tracleer.

Do not take Tracleer with glyburide because it may increase your chance of liver injury. Do not take Tracleer with cyclosporine-A because it may increase your chance of side effects.

Please see Additional Safety Information.
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Learn more about the signs and symptoms of PAH

REFERENCES:

1. Gaine SP, Rubin LJ, Primary pulmonary hypertension. Lancet. 1998;352:719-25.
2. McLaughlin VV. ACCF/AHA 2009 expert consensus document on pulmonary hypertension. J Am Coll Cardiol. 2009;53:1573-619.
3. Goraca A. New views on the role of endothelin. Endocrine Regulations. 2002;36:161-167.