About PAH

The Difference Between PH and PAH

Pulmonary hypertension (PH) is high blood pressure in the blood vessels of the lungs. PH is not a disease by itself, but rather a result of an underlying condition, such as left heart dysfunction, chronic lung disease, pulmonary embolism or other conditions associated with PH.²  PH is treated by addressing the underlying condition.²

Pulmonary arterial hypertension (PAH), on the other hand, is a less common form of PH that is a disease of the pulmonary arteries themselves. PAH can lead to right heart failure and, if left untreated, has a poor survival rate.³

What is PAH?

In a person with PAH, the pulmonary arteries (blood vessels) that carry blood from the heart to the lungs, picking up oxygen to deliver to the rest of the body, become too narrow. It is not entirely understood why this happens, but what is known is that in people with PAH, the pulmonary arteries constrict and the walls of the vessels start to change through a process called remodeling. Cells change and begin to build up on artery walls, which makes them thicker and restricts blood flow.² This makes it more difficult for the heart to pump blood through the pulmonary arteries into the lungs, robbing the body of much needed oxygen.

This process also puts extra strain on the right side of the heart, the side that pumps blood through the pulmonary arteries into the lungs, as it works harder to try and do its job. Over time, this can cause the right side of the heart to become larger and the walls of the heart thicker. These effects can lead to symptoms of PAH, as well as right ventricular failure.⁴

A Helpful Analogy

Think of your main pulmonary artery like a garden hose. When healthy, the hose (pulmonary artery) allows water (blood) to flow freely into the lungs. Now let's say the hose gets squeezed together and the water starts to have trouble getting through. Less water is able to pump out of the end of the hose.This causes the pressure in the hose to rise as the pump (heart) continues to try to get the water through despite the blockage.This puts strain on the inside of the hose as water spurts through it at a higher pressure. Eventually, the inside of the hose becomes damaged and might start to leak or break down, or the pump gives out from working too hard. This is similar to what happens inside your pulmonary arteries with PAH.

PAH and Your Blood Vessels

Watch this short video to see how PAH affects your blood vessels.

Next: Learn About Symptoms of PAH