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Understanding Pulmonary Arterial Pressure: mPAP, PCWP, and How They Impact Treatment

Medically reviewed by Steven C. Pugliese, M.D.
Posted on May 7, 2024

  • Two procedures — right heart catheterization and transthoracic echocardiography — measure pulmonary arterial pressure.
  • Health care providers use mean pulmonary artery pressure (mPAP), pulmonary capillary wedge pressure (PCWP), and pulmonary vascular resistance (PVR) to help classify your type and severity of pulmonary hypertension (PH) and determine the best treatment.
  • Talk to your health care provider if you have questions about your test results and what they mean for your PH.

If you’ve been diagnosed with pulmonary arterial hypertension (PAH) or another type of pulmonary hypertension, you know that many tests are involved in getting to that diagnosis. With so many different types of tests, it can be hard to know what each one means.

Pulmonary arterial pressure is a measurement that helps your health care providers understand the type and severity of PH you have. With this information, you and your provider can pick the best treatment plan for you.

Continue reading to learn about pulmonary arterial pressure, how it’s measured, and how your health care provider can use this information to find the best treatment for you.

What Is Pulmonary Arterial Pressure?

Pulmonary arterial pressure is a measurement of the force of blood pushing on the walls of the arteries in your lungs. If you have PAH, your pulmonary arterial pressure may be higher than normal. This is because, in PAH, the small arteries in the lungs are thicker and narrower, making it more difficult for blood to pass through them.

When your blood has a harder time passing through the small arteries in your lungs, it increases the force or pressure that blood puts on the walls of these blood vessels. Because your heart and lungs are connected, it also makes your heart work harder to push your blood through these arteries.

Your health care provider may order a test to measure your pulmonary arterial pressure to help diagnose or monitor PAH.

How Is Pulmonary Arterial Pressure Measured?

Two procedures — right heart catheterization and transthoracic echocardiography — can measure your pulmonary arterial pressure and help your provider understand how your blood flows between your heart and lungs (also called hemodynamics).

Right Heart Catheterization

Pulmonary arterial pressure is usually measured during a procedure called right heart catheterization. This procedure directly measures the pressure inside your pulmonary arteries and is the most accurate way to get a PH diagnosis. Most people with PH will undergo this procedure at least once.

Right heart catheterization is usually performed by a cardiologist (doctor who specializes in treating heart conditions). During this procedure, the doctor will guide a thin, flexible tube (called a catheter) from a large blood vessel in your neck or groin to the right side of your heart. When the catheter is in your heart, your doctor can measure your blood pressure in your right atrium, right ventricle, and pulmonary artery.

Many people with PH will undergo a right heart catheterization at least once.

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The measurements taken from right heart catheterization make up your hemodynamic profile, which can be used to learn which type of pulmonary hypertension you have and how severe it is.

Some of the measurements taken during a right heart catheterization include:

  • Mean pulmonary artery pressure — The pressure in your pulmonary artery
  • Pulmonary capillary wedge pressure — The pressure in your heart’s left atrium (left atrial pressure)
  • Cardiac output — The amount of blood your heart can pump in one minute
  • Oxygen saturation — The amount of oxygen in your blood

We’ll discuss mPAP and PCWP in more detail, below.

Transthoracic Echocardiography

Another way to measure pulmonary arterial pressure is with a procedure called transthoracic echocardiography (echocardiogram). This procedure uses sound waves to create an image of your heart.

Unlike a right heart catheterization, transthoracic echocardiography can only give an estimate of your pulmonary arterial pressure. Instead of a mPAP, echocardiography provides a measure of the pressure in your pulmonary arteries when your heart beats — known as your systolic pulmonary arterial pressure (sPAP).

If you have an echocardiography test, you may need a right heart catheterization later. As a myPHteam member shared, “I saw the pulmonologist, and he suggested I consult with a cardiologist and have this right-side heart catheterization, which he says will give a more accurate reading. An echo is an estimated reading.”

What Is Mean Pulmonary Arterial Pressure?

Your mPAP is a measure of the pressure in your pulmonary artery taken during a right heart catheterization. You’ll see that mPAP is measured in millimeters of mercury (mm Hg) — a measure of pressure. In someone without PH, mPAP is usually between 8 mm Hg and 20 mm Hg.

If you have PH, your mPAP will be higher than normal, ranging from mild to severe. Talk to your health care provider about what your results mean. As a myPHteam member shared, “My pressure was 50 and I was told I have severe pulmonary arterial hypertension.”

What Is Pulmonary Capillary Wedge Pressure?

PCWP is an estimate of the pressure in your heart’s left atrium. It may also be referred to as pulmonary artery wedge pressure.

A normal PCWP is considered to be 15 mm Hg or less. PCWP may be normal in people with some types of PH, called precapillary PH. However, PCWP may be elevated in people with PH due to left heart disease.

PCWP may be elevated in people with PH due to left heart disease or unknown causes.

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Your health care provider can use PCWP to calculate other important measurements to help classify and monitor your PH, including pulmonary vascular resistance (PVR).

What Is Pulmonary Vascular Resistance?

PVR is a calculation of the resistance your blood faces when flowing from the veins in your lungs to your heart. Your health care provider can calculate PVR using your measurements of mPAP, PCWP, and cardiac output from a right heart catheterization.

PVR uses a unique measurement system called Wood units (WU), named after the man who first described it, Paul Wood. A normal PVR is 0.3 WU to 2 WU. People with PH have a PVR higher than 2 WU.

How Do mPAP, PCWP, and PVR Impact Treatment?

Measurements, such as mPAP, PCWP, and PVR, are important determinants your health care provider will consider when suggesting a PH treatment plan for you.

These measurements can help define the severity and type of PH you have. Your hemodynamic profile helps your doctor predict if you might be at risk of serious health problems like heart failure in the next year. This information is used to determine if you may need more advanced treatments like lung transplantation.

Your mPAP measurement can be used to predict if certain treatments will work for you. During a right heart catheterization, your cardiologist may perform a vasoreactivity test (also called a vasodilator test) to see if calcium channel blockers will work for you. During this test, you’ll inhale a vasodilator (a drug that causes blood vessels to expand) while your doctor looks at your mPAP measurement. If your mPAP decreases by at least 10 mm Hg to reach a value below 40 mm Hg, calcium channel blockers may be a good treatment option for you.

PVR can also be used to monitor how well your treatment is working. In general, a reduction in your PVR after starting a treatment means it’s working well. Worsening PVR or no improvement may mean you need a new treatment. You may also see PVR measured in clinical trials for new PH treatments.

After a right heart catheterization, a myPHteam member shared, “I was told that I was no longer severe, but moderate. I am very active. I use four different medications.”

In general, a reduction in your PVR after starting PH treatment means it’s working well.

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When treating your PAH, doctors will use measurements of pulmonary arterial pressure in addition to other factors like your symptoms, how much they interfere with your daily life, and also your exercise capacity, or how much you can exercise or walk before experiencing PH symptoms. All of these factors together help a doctor better understand your PH and figure out the best treatment plan for you.

Talk With Others Who Understand

On myPHteam, the social network for people with pulmonary hypertension and their loved ones, more than 54,000 members come together to ask questions, give advice, and share their stories with others who understand life with pulmonary hypertension.

Have you had a right heart catheterization or transthoracic echocardiography? How were your mPAP and PCWP measurements affected by your treatment? Share your experience in the comments below, or start a conversation by posting on your Activities page.

References
  1. Right Heart Catheterization— To Do or Not To Do? Introducing a New Diagnostic Algorithm for Pulmonary Hypertension — Journal of the American Heart Association
  2. 2022 ESC/ERS Guidelines for the Diagnosis and Treatment of Pulmonary Hypertension: Developed by the Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS). Endorsed by the International Society for Heart and Lung Transplantation (ISHLT) and the European Reference Network on Rare Respiratory Diseases (ERN-LUNG) — European Heart Journal
  3. About High Blood Pressure — Centers for Disease Control and Prevention
  4. Right Heart Catheterization — Cleveland Clinic
  5. Learn About Pulmonary Arterial Hypertension — American Lung Association
  6. Pulmonary Arterial Hypertension — Cleveland Clinic
  7. Assessment of Pulmonary Artery Pressure by Echocardiography— A Comprehensive Review — IJC Heart & Vasculature
  8. Pulmonary Hypertension — StatPearls
  9. Diagnosing Pulmonary Hypertension — Pulmonary Hypertension Association
  10. Pulmonary Hypertension — Nationwide Children’s
  11. Revised Definition of Pulmonary Hypertension and Approach to Management: A Clinical Primer — Journal of the American Heart Association
  12. Pulmonary Capillary Wedge Pressure — StatPearls
  13. Cardiac Output — Cleveland Clinic
  14. Echocardiogram: Transthoracic (TTE) — Cleveland Clinic
  15. Pulmonary Arterial Hypertension Symptoms and Diagnosis — American Lung Association
  16. Haemodynamic Definitions and Updated Clinical Classification of Pulmonary Hypertension — European Respiratory Journal
  17. Physiology, Pulmonary Vascular Resistance — StatPearls
  18. Pulmonary Hypertension by the Method of Paul Wood — Chest
  19. Treatments — Pulmonary Hypertension Association

Posted on May 7, 2024
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Steven C. Pugliese, M.D. is affiliated with the Hospital of the University of Pennsylvania in Philadelphia, serving as the director of the pulmonary embolism response team, co-director of the comprehensive pulmonary embolism program, and an assistant professor of clinical medicine. Review provided by VeriMed Healthcare Network. Learn more about him here.
Amanda Jacot, PharmD earned a Bachelor of Science in biology from the University of Texas at Austin in 2009 and a Doctor of Pharmacy from the University of Texas College of Pharmacy in 2014. Learn more about her here.

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