Pulmonary hypertension (PH) is high blood pressure in the arteries of the lungs. PH is a general term. There are five main types of PH, based on the underlying cause of the disease. For example, pulmonary arterial hypertension (PAH) is high blood pressure in the lungs that’s caused by narrowed arteries. PAH is a specific type of PH.

Your healthcare provider will evaluate your type and class of PH when they diagnose you with the condition. Different types of PH require different treatments.

Here’s an overview of each of the five classifications of PH and how they affect the body.

Normal Heart and Lung Function

To understand PH, it helps to know how your heart and lungs work together.

Your heart has four sections of muscle, called chambers. These chambers hold blood for a short time until signals from the heart make it move through the body. The top chambers are called atria (one on the left and one on the right). The bottom two chambers are called ventricles (also one on each side).

Blood flows from the right side of the heart to the lungs. In the lungs, the blood receives oxygen. Then, the oxygen-rich blood travels to the left side of the heart, where it’s pumped out to the rest of the body.

When the right atrium of the heart receives blood that doesn’t have much oxygen, it moves it into the right ventricle. The right ventricle pumps that blood into the lungs through the left and right pulmonary arteries. In the lungs, the blood moves through smaller and smaller blood vessels in the lungs until it picks up oxygen.

As blood moves through the arteries near the lungs, it places pressure on their inner walls. This is called pulmonary pressure. If the pressure in the arteries becomes too high, the heart works harder to push blood through them. Over time, this extra strain can damage both the heart and the lungs.

Once the blood gets oxygen to the lungs, it goes back to the left atrium through the pulmonary veins. The left atrium then sends it to the left ventricle, which is the heart’s largest and strongest chamber. It’s responsible for sending blood around the body.

Your heart also has four heart valves: mitral, aortic, tricuspid, and pulmonary. These valves act like doors that open to let blood flow between each chamber of the heart and through the lungs. The valves open to let blood move forward and snap shut to prevent it from moving backward.

What Are the 5 Groups of Pulmonary Hypertension?

The World Health Organization (WHO) groups PH into five main groups, or types, based on their cause.

Group 1: Pulmonary Arterial Hypertension

This type of PH develops when the pulmonary arteries (the ones that send blood from your heart to your lungs) become narrow and stiff. That makes it harder for blood to flow through. It usually happens because the walls of the arteries get thicker and inflamed. There are several kinds of PAH:

• Idiopathic PAH — Has no known cause
• Heritable PAH — Was passed down from a parent
• Drug- or toxin-induced PAH — Caused by exposure to a medication, stimulants (like methamphetamine), or toxins
• Associated PAH — Caused by another disease

Diseases that can cause associated PAH include:

• Congenital (present at birth) heart disease
• Connective tissue diseases like lupus or scleroderma
• HIV infection
• Portal hypertension
• Schistosomiasis (a parasitic infection)

Group 2: Pulmonary Hypertension Caused by Left-Sided Heart Disease

This is the most common type of PH in the United States. It happens when PH is caused by left heart disease.

Left heart disease is when there is a problem with the left side of the heart, especially the left ventricle, which is the heart’s main pumping chamber. When disease damages the left ventricle, it can’t pump blood to the rest of the body properly. This means the blood doesn’t get new oxygen fast enough. As a result, deoxygenated blood backs up into the lungs, causing high blood pressure in the pulmonary arteries. This backup of blood is often called congestive heart failure.

Other types of heart disease that may cause this type of PH include:

• Mitral valve problems
• Aortic valve problems
• Coronary artery disease (CAD)
• Congenital heart disease
• Chronic (long-term) high blood pressure throughout the body

Treating the underlying heart disease can help relieve symptoms of this type of PH.

Group 3: Pulmonary Hypertension Caused by Lung Disease

Group 3 PH happens when lung disease or sleep-disordered breathing causes chronic hypoxia, or low oxygen levels. Conditions that can cause group 3 PH include:

• Chronic obstructive pulmonary disease (COPD)
• Restrictive lung diseases (like interstitial lung disease)
• Sleep apnea
• Other lung diseases.

Some people can also get group 3 PH from living at high altitudes, where oxygen is lower.

Group 3 PH can be treated with supportive oxygen therapy to help raise oxygen levels in the blood. If the PH is caused by COPD, medications called bronchodilators, which help widen airways, are important. For severe PH, a lung transplant might be considered.

Group 4: Pulmonary Hypertension Caused by Blood Clots in the Lungs

Also known as chronic thromboembolic PH (CTEPH), group 4 PH is caused by blood clots that have become stuck in the pulmonary arteries. These clots block blood flow and raise the blood pressure in the lungs, leading to PH symptoms.

CTEPH can be treated with surgery. However, not everyone with CTEPH is a good candidate. Because blood clots cause group 4 PH, treatment options include blood thinners.

Group 5: Pulmonary Hypertension Due to Unknown Causes

Group 5 PH develops when the exact cause of PH isn’t clear, or when it’s caused by several other underlying diseases or health factors. Any condition that interferes with the movement of blood flow through the lungs can cause PH.

The best way to treat group 5 PH is to address the health condition that’s causing it, if it can be found.

Some conditions that can cause group 5 PH include:

• Chronic hemolytic anemia (a condition where red blood cells break down too quickly)
• Chronic kidney failure
• Fibrosing mediastinitis (noncancerous growths in the chest area)
• Gaucher’s disease or glycogen storage disease (genetic disorders)
• Leukemia (a type of blood cancer)
• Polycythemia vera and thrombocythemia (blood disorders)
• Sarcoidosis (inflammation in the lungs or other organs)
• Tumors that compress the pulmonary arteries

If doctors can figure out the condition that is causing the PH, treating it will help PH symptoms in this group.

Talk With Others Who Understand

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

What type of PH do you have? How does your type of PH affect your quality of life? Share your experience in the comments below, or start a conversation by posting on your Activities page.