Understanding PAH

What is Pulmonary Arterial Hypertension (PAH)?

PAH is a disease in which the pressure in a patient's pulmonary arteries becomes dangerously high. Pulmonary arteries carry blood that has returned from the body to the lungs, where the blood receives a fresh supply of oxygen. That high blood pressure puts a strain on the heart.  PAH is one of five types of pulmonary hypertension (PH).  PAH worsens over time and is life-threatening. It is a relatively rare disease, affecting 1 in 100,000 to 1 in 1 million people.

There are several types of PAH:

Idiopathic (IPAH)—PAH in which the cause is unknown

Familial (FPAH)—PAH that runs in families and often is linked to a genetic defect

Associated (APAH)—the most common type of PAH, which is caused by or occurs at the same time as other medical conditions, including:

  • Collagen vascular disease (or connective tissue disease)--includes autoimmune diseases such as scleroderma or lupus; in autoimmune diseases, the body's immune system mistakenly attacks its own cells and tissues
  • Congenital heart and lung disease—heart/lung diseases that develop at or before birth
  • Portal hypertension—a condition usually resulting from liver disease
  • HIV infection
  • Drugs—including appetite suppressants, particularly fenfluramine and dexfenfluramine; cocaine or amphetamines; other drugs
  • Other conditions:  thyroid disorders, glycogen storage disease (genetic defect in forming or releasing sugars necessary for the body to function), Gaucher disease (an inherited metabolic disorder), hereditary hemorrhagic telangiectasia (abnormally formed blood vessels resulting in excessive bleeding), hemoglobinopathies (abnormally formed oxygen carrying protein in the red blood cells, caused by a genetic defect), myeloproliferative disorders (overproduction of red or white blood cells) and splenectomy (removal of the spleen)

Associated with significant venous or capillary involvement—PAH occurring at the same time as abnormal narrowing in the pulmonary veins and/or capillaries and may or may not include arteries; conditions include:

  • Pulmonary veno-occlusive disease (PVOD): a disease resulting in blockage  of the veins in the lungs
  • Pulmonary capillary hemangiomatosis:  small blood vessels in the lungs grow too much and become tangled, resulting in poor blood flow

Persistent pulmonary hypertension of the newborn—PAH in newborn's when the heart and blood vessels do not adapt to breathing outside the womb.

 What Causes PAH?

Blood pressure in the pulmonary arteries increases when the small arteries of the lungs become abnormally narrow.  This can be caused by three types of changes in the body:

  • The muscles within the walls of the arteries may contract—or squeeze--making it harder for blood to flow through them.
  • The walls of the arteries may thicken from too much cell growth in the lining of the vessels.
  • Tiny blood clots may form within the smaller arteries, blocking the flow of blood.

Any of these changes make it difficult for blood to pass through the lungs. When that happens, the heart is forced to work too hard.  Over time, the heart muscle weakens and can no longer pump blood efficiently. When the heart can no longer effectively pump blood and deliver oxygen to all parts of the body, patients with PAH feel symptoms—shortness of breath, fatigue, chest pain, dizziness, fainting and others. 

If PAH is not treated, the heart will fail eventually, leading to severe disability and even death.

Who gets PAH?

  • PAH is more common in women than men overall and affects people of all ages and all ethnic and racial backgrounds.
  • PAH is likely to get worse during labor and delivery and sometimes causes maternal death.
  • PAH also is found more often in people with a family history of pulmonary hypertension or sudden death.
  • Persistent pulmonary hypertension of the newborn (PPHN) causes acute or sudden respiratory failure in newborns. It is most common among full-term infants who have other diseases. Those diseases include respiratory distress, sepsis or lung hypoplasia (below normal size or immature).
  • Scientists believe a person's chances of developing PAH increases depending on certain factors. Those include use of appetite suppressant drugs (especially fenfluramine and dexfenfluramine), chronic use of cocaine or amphetamines, HIV infection, liver disease and connective tissue diseases such as scleroderma or lupus erythematosus.

Studies estimate that the use of certain appetite suppressant drugs increases the risk of getting PAH more than six times. Fenfluramine and dexfenfluramine were taken off the market in September 1997 after being linked to heart valve damage.

How Serious is PAH?

There is no cure for PAH, and it worsens over time.

Approximately 50 percent of people diagnosed with PAH die within five years. For people whose PAH is not treated, average survival is only about three years.

Even with treatment, the pressure in the lungs caused by PAH will continue to worsen and make everyday tasks more difficult. But many patients make lifestyle changes that allow them to go about many of their daily tasks.

Doctors identify how severe a patient's PAH is and decides on treatment based on that person's "functional status". Functional status is a person's ability to perform everyday tasks and is ranked from Class I (no limitations) to Class IV (unable to perform any physical activity). Specifically:

  • Class I: No limitation of usual physical activity; ordinary physical activity does not cause increased breathing problems, fatigue, chest pain or lightheadedness.
  • Class II: Mild limitation of physical activity; there is no discomfort when the person is at rest, but normal physical activity causes increased breathing problems, fatigue, chest pain or lightheadedness.
  • Class III: Marked limitation of physical activity; there is no discomfort when the person is at rest, but less than ordinary physical activity causes increased breathing problems, fatigue, chest pain or lightheadedness.
  • Class IV: Unable to perform any physical activity and possible signs of heart failure in the right ventricle (the chamber of the heart that pumps blood to the lungs); at rest, patients have difficulty breathing and/or fatigue, and symptoms get worse by almost any physical activity.