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What Is Pulmonary Artery Occlusion Pressure?

Medically reviewed by Angelica Balingit, M.D.
Written by Emily Wagner, M.S.
Posted on October 20, 2023

Receiving a diagnosis of pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) can leave you feeling overwhelmed. With so many new complex medical terms to learn, you might not even know where to start.

One measurement your doctor may take to diagnose PH or PAH is your pulmonary artery occlusion pressure (PAOP). It gives an estimated pressure measurement for the left side of your heart, which is important for determining what’s causing your PH.

This article will cover what you need to know about PAOP and what the results mean for your treatment plan. If you’re interested in learning more about your PAOP measurement for your PH, ask your doctor at your next appointment.

Understanding the Connection Between Your Heart and Lungs

To better understand what PAOP is and why it’s measured, it helps to first learn how your heart and lungs wohttps://www.myphteam.com/resources/whats-the-connection-between-the-lungs-and-heartrk together. These organs move oxygen-rich blood and nutrients out to the rest of your body and bring it back to your lungs to be replenished. Your heart is made of four chambers — two atria at the top, and two ventricles at the bottom.

Your heart and lungs work together to bring oxygenated blood and nutrients to the rest of your body. In pulmonary hypertension, the blood vessels between the heart and lungs become hard and narrow, leading to high blood pressure and forcing your heart to work harder to pump blood. (Adobe Stock)

The right atrium takes the oxygen-poor blood from your body, carried by the superior vena cava, and pumps it into the right ventricle. This chamber moves blood into your pulmonary arteries — the main blood vessels responsible for bringing blood into your lungs. Once inside the lungs, carbon dioxide is removed from the blood and replaced with oxygen.

The blood moves to your left atrium and through a set of tissue flaps known as the mitral valve. They keep it flowing in the correct direction and stop it from flowing backward. Finally, the oxygen-rich blood is pumped to your left ventricle and through your aorta to the rest of your body.

What Is PAOP and What Does It Mean in PH?

Normally, your pulmonary arteries are relaxed to let as much blood flow through as possible. There isn’t much pressure or resistance in these arteries. When you have PH, the blood pressure level in your pulmonary arteries is too high. Your heart has to work harder to pump blood through your pulmonary arteries, which eventually weakens the muscle.

PAOP is an important piece of information used to diagnose PH and PAH. Also known as pulmonary artery wedge pressure (PAWP) or pulmonary capillary wedge pressure (PCWP), it’s a blood pressure measurement taken within your pulmonary artery.

It’s important to note your PAOP doesn’t measure the pressure in your arteries. Instead, it helps estimate the pressure in your left atrium. This measurement helps your doctor determine if your PH is caused by an issue on the left side of your heart or something else. An elevated PAOP measurement means fluid is backed up in your lungs, leading to a life-threatening condition called pulmonary edema. Over time, uncontrolled edema can lead to PH.

How Is PAOP Measured?

In order to measure your PAOP, your doctor will perform a right-heart catheterization — the gold-standard test for diagnosing PH and PAH. They’ll use a long, thin tube known as a catheter with a balloon attached to the end. Your doctor will insert the catheter into a large vein — either in your leg or neck — and guide it into your right atrium.

The catheter will then travel through your heart and into your pulmonary artery. The balloon at the end is positioned or “wedged” in the branch of the artery, where it splits to the left and right lungs. A pressure sensor is attached to measure blood pressure in the artery. It measures the amount of pressure it takes to fill the balloon up — this reading is an estimate of your left atrial pressure.

While the catheter is placed, your doctor will also measure the amount of blood your heart pumps every minute. Known as your cardiac output, this measurement can also be affected by PH or PAH.

Another important measurement taken alongside PAOP is your mean pulmonary artery pressure (mPAP). This is an average measurement of the pressure in your pulmonary arteries. While your doctor can use Doppler echocardiography to estimate your mPAP, an accurate measurement is typically taken during right-heart catheterization.

Measuring Pulmonary Vascular Resistance

Your doctor will use your mPAP, PAOP, and cardiac output measurements to calculate pulmonary vascular resistance (PVR). Your PVR refers to the resistance against blood flowing from your pulmonary arteries to the left atrium. You may see your PVR reported on your test results in Wood units (a way to measure how hard it is for blood to flow through the vessels in the lungs).

A healthy PVR is typically less than 2 Wood units. High blood pressure in your pulmonary arteries makes your PVR higher. It also means your heart has to work harder to pump against the resistance. An elevated PVR measurement is associated with PAH.

Why Is PAOP Important When Diagnosing PH and PAH?

Your PAOP measurement can be the key to determining the driving force behind your PH or PAH symptoms. Your doctor needs to find the root cause of your PH or PAH so they can properly treat it.

You’ll be diagnosed with PH if your mPAP is 20 millimeters of mercury (mm Hg) or higher. If it’s between 21 and 24 mm Hg, you may receive or have received a diagnosis of “borderline PH,” based on 2015 guidelines for defining the condition from the American Heart Association, European Society of Cardiology, and European Respiratory Society. (Under their 2022 guidelines, “borderline PH” has been eliminated, and an mPAP of 20 mm Hg is a criterion for a PH diagnosis.)

Under these 2022 guidelines, PAH (also known as group 1 PH), is specifically diagnosed when you:

  • Don’t have left heart disease or lung disease causing your PAH
  • Have an mPAP measurement of 20 mm Hg or higher
  • Have a PAOP measurement of 15 mm Hg or less
  • Have a PVR measurement greater than 2 Wood units

On the other hand, an elevated mPAP and a PAOP measurement higher than 15 mm Hg may mean your PH is actually caused by a heart problem. It’s most likely an issue with your aorta, mitral valve, or left ventricle.

How Do PAOP Measurements Affect Your PH Treatment Plan?

Once your doctor confirms your PH or PAH, they’ll work on creating the best treatment plan for you. It’s important to understand why your PH or PAH developed in the first place in order to treat it.

PH Caused by Left-Sided Heart Disease

If your PAOP measurement shows you may have a heart problem causing your PH, your doctor can run more tests to find out exactly what’s wrong.

For example, an issue with your aorta or mitral valve in PH is likely a sign that you’re in heart failure. Dysfunction in the left side of your heart means it can’t pump out oxygenated blood to the rest of your body. This blood builds up in your heart and puts pressure on the pulmonary arteries behind it — like a traffic jam on a highway.

Examples of issues that may be driving your PH include:

  • Aortic regurgitation — The aortic valve doesn’t close properly, allowing blood to flow back into the left ventricle.
  • Mitral regurgitation — The mitral valve doesn’t close properly, letting blood flow back into the left atrium.
  • Aortic stenosis — The aortic valve narrows, making it harder for the left ventricle to pump blood.
  • Mitral stenosis — The mitral valve narrows, requiring the left atrium to pump harder.

If you’re living with a left heart issue and PH, your doctor can repair or replace the damaged valve causing problems. You’ll also be treated with blood pressure medications to take pressure off your heart and lower your pulmonary artery pressure.

PAH From Underlying Health Conditions

Likewise, PAH is often caused by several underlying health conditions. By finding out which is responsible for your symptoms, your doctor can help you better manage it. Examples include:

  • Liver disease
  • Congenital heart disease (birth defects in your heart)
  • Connective tissue diseases like lupus or scleroderma
  • Infection with HIV

Talk With Others Who Understand

On myPHteam, the social network for people with pulmonary hypertension and their loved ones, more than 51,000 members come together to ask questions, give advice, and share their stories with others who understand life with pulmonary hypertension.

Have you had pulmonary artery occlusion pressure measurements taken? How did they play a role in your pulmonary hypertension diagnosis? Share your experience in the comments below, or start a conversation on your Activities page.

References
  1. Effect of Balloon Inflation Volume on Pulmonary Artery Occlusion Pressure in Patients With and Without Pulmonary Hypertension — Chest
  2. How the Lungs Work: The Respiratory System — National Heart, Lung, and Blood Institute
  3. Heart Chambers — Cleveland Clinic
  4. Pulmonary Arteries — Cleveland Clinic
  5. Pulmonary Artery Occlusion Pressure: Measurement, Significance, and Clinical Uses — Update in Intensive Care and Emergency Medicine
  6. Pulmonary Hypertension (PH) — Cleveland Clinic
  7. Pulmonary Capillary Wedge Pressure — Cardiovascular Physiology Concepts
  8. Pulmonary Edema — Mayo Clinic
  9. Pulmonary Hypertension — UPMC
  10. Measurement of Cardiac Output — Cardiovascular Physiology Concepts
  11. Mean Pulmonary Artery Pressure — Radiopaedia
  12. Accuracy of Doppler-Echocardiographic Mean Pulmonary Artery Pressure for Diagnosis of Pulmonary Hypertension — PLOS One
  13. Pulmonary Vascular Resistance — Lippincott NursingCenter
  14. Pulmonary Arterial Hypertension With Below Threshold Pulmonary Vascular Resistance — European Respiratory Journal
  15. The Association Between Pulmonary Vascular Resistance and Clinical Outcomes in Patients With Pulmonary Hypertension: A Retrospective Cohort Study — The Lancet Respiratory Medicine
  16. 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
  17. Pulmonary Arterial Hypertension — Cleveland Clinic Center for Continuing Education
  18. Pulmonary Hypertension in Aortic and Mitral Valve Disease — Frontiers in Cardiovascular Medicine

Posted on October 20, 2023
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Angelica Balingit, M.D. is a specialist in internal medicine, board certified since 1996. Learn more about her here.
Emily Wagner, M.S. holds a Master of Science in biomedical sciences with a focus in pharmacology. She is passionate about immunology, cancer biology, and molecular biology. Learn more about her here.

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