What Is PAH?

A specific type of high blood pressure

PAH is the medical abbreviation for pulmonary arterial hypertension. PAH is a specific type of high blood pressure that affects your heart and lungs. When you have PAH, the blood vessels in your lungs become narrower. This means your heart has to work harder to pump blood to your lungs.

What’s the difference between PAH and high blood pressure?

You may know someone who has “high blood pressure” that they might be treating with medication. PAH is a form of high blood pressure in your lungs, and it’s a serious condition. PAH is progressive, it worsens over time, and it’s eventually fatal. But it can be treated with medication, so people with PAH can address their symptoms and possibly live longer. The PAH Basics video explains what happens in your body when you have PAH.

High blood pressure in the lungs with magnified closeup showing narrowed blood vessels

When you have PAH, the blood vessels in your lungs become narrower, causing your heart to work harder to pump blood to your lungs.

PAH can be confusing

You may hear different things about PAH. In this PAH Basics video, Dr. Lana Melendres-Groves explains what PAH is and how it affects your heart and lungs.  

Click to expand transcript

[Video title: PAH Basics, Part 1 in the PAH Initiative Video Series] Hi, I’m Dr Lana Melendres-Groves, a pulmonary arterial hypertension specialist and director of the pulmonary hypertension program at the University of New Mexico. I have been treating pulmonary diseases for over 12 years with a specialization in PAH for over 9 years. My clinic has treated over 5,000 patients and I currently oversee 250 PAH patients on PAH-specific medicines. In this video, we’ll cover the basics of pulmonary arterial hypertension, also known as PAH. Understanding what PAH is can be confusing because even healthcare providers may tell you different things about it. Some may say your heart doesn’t work as well as it needs to. It’s really about the blood vessels. The real problem is in the lungs or it’s just hypertension. This is why it’s so important to find an experienced PAH specialist to help you. A PAH specialist is a cardiologist or pulmonologist who has had specific training in PAH and understands how challenging this disease really is.

The heart, lungs, and blood vessels all work together as a cardiovascular team and PAH affects each of these vital organs. So let’s start with the heart. You may already know that the heart has 4 chambers. Two chambers are called atria and receive blood from the other parts of the body and the other 2 chambers are called ventricles and pump blood out of the heart. The right atrium receives blue, oxygen-poor blood from the body and the right ventricle pumps that oxygen-poor blood to the lungs where it can pick up oxygen. The left atrium receives red, oxygen-rich blood from the lungs and then the left ventricle pumps the oxygen-rich blood to the rest of the body. Although cardiac diseases, including heart attacks, are more common in the left ventricle, it’s actually the right ventricle that is affected in people who have PAH.

[End of video: PAH Initiative, Sponsored by United Therapeutics, Committed to Improving the Lives of Patients. For more resources about PAH, please visit www.PAHInitiative.com. Copyright 2019 United Therapeutics Corporation. All rights reserved.]

What’s going on with your heart?

Knowing how your heart and lungs work together will help you understand what happens in your body when you have PAH.

The heart is divided into 2 sides, the right and the left. Click on the dot to learn what each chamber does.

Right atrium Right ventricle Left atrium Left ventricle

Right atrium

Blood entering the right atrium has just finished delivering oxygen to the tissues and cells in your body. So, the blood in this atrium is oxygen-poor blood.

Right ventricle

Oxygen-poor blood passes from the right atrium into the right ventricle. This ventricle pumps blood to vessels in the lungs, where the blood “resupplies” with oxygen. This ventricle pumps blood only to the lungs.

Left atrium

After the right side of the heart does its job and pumps blood through the lungs to pick up oxygen, the blood flows from the lungs and re-enters the heart through the left atrium.

Left ventricle

Then, the left ventricle pumps the oxygen-rich blood to the cells and tissues throughout the entire body. This cycle occurs continuously.

The heart and lung connection

When you have PAH, the blood vessels in your lungs thicken and become narrow, making your heart work harder to pump blood through them.

Discover how PAH treatment options help keep blood vessels open and help to improve your symptoms.

Click to expand transcript

PAH begins when the walls of the blood vessels in the lungs thicken and become more narrow. Because the blood vessels become more narrow, it’s harder for the blood to pass through them. The reduced blood flow that is caused by the narrowed vessels creates increased pressure on the right side of the heart. The right side of the heart tries to compensate by working harder to pump blood through the vessels and into the lungs. Over time, the heart struggles to maintain this level of intensity. It’s like asking your heart to run a marathon every minute of every day and PAH symptoms result.

PAH narrowing blood vessels traffic jam visual

Think of PAH like construction on a highway

Imagine your blood vessels as the highway. Your blood cells are like the cars. When blood vessels in the lungs become narrow, the flow of blood cells is reduced—similar to the way traffic flow slows down when lanes are closed. 

That’s why you feel symptoms of PAH 

The right side of your heart works harder to pump blood through the narrow blood vessels of your lungs. As this is happening, you may feel symptoms—like lightheadedness or shortness of breath—because less blood and oxygen reach the parts of your body where they’re needed. Over time, your heart wears down and eventually fails.

What causes PAH?

Your doctor might not be able to find a reason for your PAH. This is called idiopathic PAH. The word idiopathic describes any disease that develops for unknown reasons. The cause also could be genetic—a gene mutation can cause PAH to develop within families.

Other factors that can cause or contribute to PAH include:

  • Congestive heart failure
  • Blood clots in the lungs
  • HIV
  • Drug use (including methamphetamine or cocaine)
  • Liver disease (such as cirrhosis)
  • Autoimmune diseases (eg, lupus, scleroderma, or rheumatoid arthritis)
  • Heart defects
  • Lung disease (such as emphysema or chronic bronchitis)
  • Sleep apnea
PAH causes

How common is PAH?

Only about 1,000 new cases per year in the US

PAH is rare—only about 1,000 new cases of PAH are diagnosed every year in the United States. PAH is more common in women than in men.

PAH is chronic, and it gets worse over time. But life expectancy has been improving for people with PAH. In addition, treatment options and current approaches to care, such as improving your risk status, continue to advance.

What’s the difference?


You may hear your healthcare providers say “PH” or “PAH.” What’s the difference?

PH (pulmonary hypertension) is a general way to describe high blood pressure in the lungs, which could occur for a variety of reasons.

PAH (pulmonary arterial hypertension), on the other hand, is a specific type of PH. PAH describes high blood pressure that happens for a very specific reason: The blood vessels in your lungs have become narrow. PAH can be fatal, but with early diagnosis and appropriate treatment, you might be able to improve your life expectancy.

Finding a PAH expert

PAH is a rare disease. Because it’s rare, not all heart specialists (cardiologists) or lung specialists (pulmonologists) in your community have experience treating PAH. For this reason, people with PAH are encouraged to seek out a healthcare provider and treatment team with expertise in treating PAH. You can search for a PAH expert through the Pulmonary Hypertension Association.

Find an Expert

PAH knowledge is PAH power

True or false? PAH is a type of high blood pressure caused by narrow blood vessels in the lungs.

When you have PAH, which ventricle of your heart works harder to pump blood to the vessels in the lungs?

Symptoms of PAH can be difficult to notice at first

If you have PAH, your healthcare provider will continually monitor your symptoms because they are an important source of information.

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