Pulmonary hypertension is abnormally high blood pressure in the arteries that carry blood from your heart to your lungs. It’s defined as a mean pulmonary arterial pressure above 20 mmHg, measured during a procedure called right heart catheterization. That threshold was lowered from 25 mmHg in 2018 to capture more people at risk for progression. Unlike regular high blood pressure, which affects arteries throughout your body, pulmonary hypertension specifically strains the right side of your heart, which has to pump harder to push blood through narrowed or stiffened lung vessels.
What Happens Inside the Lungs
In a healthy circulation, blood flows easily through the pulmonary arteries, picks up oxygen in the lungs, and returns to the left side of the heart for distribution to the body. In pulmonary hypertension, the walls of those lung arteries change. The smooth muscle cells lining the vessel walls multiply and thicken, and the inner lining of the vessels can overgrow to the point of partially blocking the opening. These structural changes raise resistance inside the vessels, forcing the right ventricle to work progressively harder.
Over time, the right ventricle thickens and enlarges in response to that extra workload. Eventually it can weaken and fail, a condition called right heart failure. This is the primary way pulmonary hypertension becomes life-threatening.
The Five Groups of Pulmonary Hypertension
Not all pulmonary hypertension has the same cause. The World Health Organization classifies it into five groups, and knowing which group someone falls into determines how they’re treated.
- Group 1: Pulmonary arterial hypertension (PAH). This is disease of the small pulmonary arteries themselves. It includes cases with no identifiable cause (idiopathic), inherited forms, and PAH triggered by autoimmune conditions, congenital heart defects, liver disease, HIV, or certain drugs like amphetamines.
- Group 2: Left-sided heart disease. This is the most common form overall. Problems on the left side of the heart, such as heart failure, mitral valve disease, or aortic valve disease, cause blood to back up into the pulmonary veins. That backup raises pressure throughout the lung circulation.
- Group 3: Lung disease or low oxygen levels. Chronic conditions like COPD, interstitial lung disease, or sleep apnea can lead to mild elevations in pulmonary pressure. The low oxygen environment causes lung vessels to constrict.
- Group 4: Chronic blood clots in the lungs (CTEPH). Old blood clots that never fully dissolved obstruct pulmonary arteries. This form is notable because it can potentially be cured with surgery to remove the clot material, without requiring a transplant.
- Group 5: Multifactorial or unclear mechanisms. This is a catch-all for pulmonary hypertension caused by systemic diseases like sarcoidosis, certain blood disorders, or external compression of the pulmonary arteries.
Symptoms by Severity
Early pulmonary hypertension often produces no symptoms at all, which is one reason it’s frequently diagnosed late. As pressure rises, the most common first symptom is shortness of breath during physical activity. Clinicians use a four-tier functional class system to gauge severity:
In Class I, you have pulmonary hypertension but no limitation on your physical activity. Class II means ordinary activities like climbing stairs or carrying groceries cause shortness of breath, fatigue, or chest discomfort, though you feel fine at rest. Class III marks a significant shift: even light activity, less than what most people consider “ordinary,” triggers symptoms. By Class IV, symptoms occur even while sitting or lying down, and signs of right heart failure are present. Fainting (syncope) is considered a Class IV symptom.
Other common symptoms across all stages include fatigue that seems out of proportion to your activity level, dizziness, heart palpitations, swelling in the ankles or legs, and a bluish tint to the lips or skin.
How It’s Diagnosed
The process typically starts with an echocardiogram, an ultrasound of the heart. Doctors look at a measurement called the peak tricuspid regurgitant velocity, which estimates how fast blood leaks backward through a valve on the right side of the heart. A reading above 3.4 meters per second suggests a high probability of pulmonary hypertension. The echo also reveals whether the right ventricle is enlarged relative to the left, or whether the wall between the ventricles is being pushed out of its normal shape by excess pressure.
An echocardiogram can raise suspicion, but it cannot confirm the diagnosis. That requires right heart catheterization, where a thin tube is threaded through a vein into the heart and pulmonary arteries to directly measure pressures. This test distinguishes between pre-capillary pulmonary hypertension (where the problem originates in the lung vessels themselves) and post-capillary pulmonary hypertension (where the problem starts with the left side of the heart). The key dividing line is a wedge pressure of 15 mmHg: below that points to a lung vessel problem, above it points to a left heart problem. This distinction is critical because the treatments are completely different.
Treatment Approaches
Treatment depends entirely on which group of pulmonary hypertension you have. For Group 2, the focus is on treating the underlying heart condition. For Group 3, managing the lung disease and supplemental oxygen are the primary strategies. Group 4 may be treated with a surgical procedure to clear chronic clot material from the arteries.
Group 1 PAH has the most specialized drug therapy, targeting three biological pathways that go wrong in the disease. The first is the endothelin pathway: endothelin is a substance that causes blood vessels to constrict, and it’s overproduced in PAH. Drugs called endothelin receptor antagonists block its effects. The second is the nitric oxide pathway: nitric oxide normally relaxes blood vessels, but this signaling is impaired in PAH. Medications that boost nitric oxide signaling help vessels open wider. The third is the prostacyclin pathway: prostacyclin is another natural vessel relaxer that’s deficient in PAH, and drugs that mimic or enhance it can reduce pressure and improve blood flow.
Many patients with PAH end up on combination therapy, taking drugs that target two or even all three of these pathways simultaneously. Before these treatments existed, options were limited to supportive care like oxygen and blood thinners, and outcomes were far worse.
Lifestyle and Fluid Management
Because the right side of the heart struggles to handle excess volume, managing fluid balance is a core part of living with pulmonary hypertension. Most specialists recommend limiting sodium intake to 2 grams per day, which is roughly one teaspoon of table salt. This requires careful attention to food labels, since processed and restaurant foods often contain far more sodium than people realize. Many clinicians also advise a fluid restriction of about 2 liters per day, including all beverages and liquid-containing foods like soups.
Regular physical activity is encouraged, though the type and intensity should match your functional class. Light aerobic exercise and supervised rehabilitation programs have been shown to improve exercise tolerance and quality of life. Altitude and air travel can worsen symptoms because of lower oxygen levels, so supplemental oxygen during flights is sometimes necessary.
Survival and Outlook
The prognosis for pulmonary hypertension varies enormously depending on the type and how early it’s caught. For Group 1 PAH, outcomes have improved dramatically since the 1980s, when one-year survival was only about 68% and five-year survival was 36%. Modern treatment has shifted those numbers considerably. Recent data from a specialized center showed one-year survival of about 96% and five-year survival near 87%.
The underlying cause matters, too. Patients with PAH related to congenital heart disease tend to have better outcomes, with roughly 88% surviving one year and 74% at five years. Those whose PAH is linked to connective tissue diseases like scleroderma have a harder road, with five-year survival closer to 43%, partly because these patients are often diagnosed at a more advanced stage.
Group 4 CTEPH has the most optimistic trajectory for the right candidates, since surgical removal of clot material can be curative. Group 2 outcomes depend largely on how well the underlying heart disease responds to treatment. Across all groups, earlier diagnosis and prompt initiation of appropriate therapy consistently lead to better quality of life and longer survival.