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.

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 lungs

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


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.

Again, the heart, lungs, and blood vessels all work together. 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. Because sending blood to the lungs is somewhat easier than pumping blood to the entire body, the right ventricle was not designed to work quite as hard as the left, but working so hard to compensate for narrowed blood vessels causes the right side of the heart to enlarge and eventually to weaken so that it wears out and is no longer able to keep up. One analogy that can help with understanding PAH is traffic on a 5-lane highway.

The highway represents the blood vessels and the cars represent the blood cells. Watch what happens to the traffic flow when there is construction. If 2 lanes on the 5-lane highway are closed for construction, it’s harder for the cars to get through. Traffic flow slows down and the cars back up behind the lane closure, causing a traffic jam. In your body, narrowed blood vessels cause the blood flow to slow and back up into the right side of the heart as it struggles to keep up. This means less blood is able to get pushed through the lungs to pick up oxygen. Because the heart has to work harder to pump blood into the lungs, people with PAH begin to experience symptoms such as chest pain and shortness of breath. Although symptoms help doctors diagnose PAH. They are also a critical element of monitoring PAH over time.

Knowing about the symptoms you experience and when you experience them helps your healthcare provider assess whether your condition is improving, staying the same, or getting worse. This is key to determining the right treatment plan. You are likely familiar with at least some of the PAH symptoms like shortness of breath, a rapid, hard, irregular heartbeat, chest pain, swollen ankles, a swollen abdomen, or even dizziness and fainting. Over time, as the disease progresses, the symptoms get worse and you may find that you cannot do as much physically. It’s important to note that symptoms may not always reflect whether PAH is progressing or how it is affecting your body. Even if your symptoms remain the same, there still may be more you can do to help improve how you feel. Sometimes people with PAH try to ignore their symptoms until they become more extreme, but when it comes to PAH, it’s important to speak with your doctor about how you are doing.

Effectively treating PAH sooner rather than later can make a difference in how quickly your PAH progresses. So it’s important to be your own advocate and to find an experienced PAH doctor. Not all pulmonologists and cardiologists have specialized PAH training, so it’s important to find a PAH doctor who understands each of the available PAH medications.

Things to remember: PAH is a disease of high blood pressure within the blood vessels of the lungs that leads to right heart damage and eventually heart failure. The symptoms that you feel are a reflection of how your heart is struggling and they will not improve without treatment. PAH is a progressive disease, meaning that it will get worse over time, but the rate of progression varies. Be proactive by finding a doctor who specializes in PAH and ask about things you may be able to do now to reduce symptoms and help slow disease progression. I’ll leave you with this tip: Keep a symptom journal. Either on paper, on your computer, on a mobile device. That way you won’t have to try and remember everything that happens between doctor visits. This will help you and your healthcare provider determine whether your PAH symptoms are changing over time and what treatment options may be best for you.

Thank you for watching PAH Basics. Watch the next video from the PAH Initiative video series to learn about working with your PAH doctor to set goals for treatment.

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.  

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

Your heart is a muscle, and PAH puts excessive strain on it. When you have PAH, the blood vessels in your lungs thicken and become narrow.

This means the right ventricle of your heart works harder to pump blood through the narrowed blood vessels of the lungs. Over time, the right side of your heart grows larger and weakens because of how hard it must work.

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

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.