Pulmonary hypertension is diagnosed through a three-step process: suspicion based on symptoms, detection using an echocardiogram, and confirmation with a procedure called right heart catheterization. A confirmed diagnosis requires a mean pulmonary arterial pressure above 20 mmHg, measured directly inside the heart. Because the symptoms overlap with many other conditions, reaching a final diagnosis often takes months and involves multiple tests to both confirm the disease and identify its underlying cause.
Why Diagnosis Takes Time
The earliest symptoms of pulmonary hypertension, such as breathlessness during activity, fatigue, and dizziness, are easy to attribute to being out of shape, aging, or other heart and lung conditions. There is no single blood test that confirms it. Instead, the diagnostic process works like a funnel: broad screening first, then increasingly specific tests to measure the pressures in your lungs and figure out which of five distinct types you have. That classification matters because each type has a different cause and a different treatment approach.
The Echocardiogram: First Real Test
An echocardiogram is the primary screening tool. It uses ultrasound to look at the structure and function of your heart, and it can estimate the pressure in your pulmonary arteries without any needles or catheters. The key measurement is something called the tricuspid regurgitation velocity, which tracks how fast a small jet of blood leaks backward through one of your heart valves. That speed correlates with the pressure in your lungs.
Current guidelines sort the results into three probability levels. A peak velocity of 2.8 meters per second or lower suggests a low probability of pulmonary hypertension. Between 2.9 and 3.4 m/s is intermediate. Above 3.4 m/s is high probability. An intermediate or high result doesn’t confirm the diagnosis on its own, but it triggers the next round of testing. The echocardiogram also reveals other clues: whether the right side of the heart is enlarged, whether the wall between the chambers is bowing in an unusual direction, or whether the right ventricle is struggling to pump effectively.
Blood Tests and Biomarkers
Blood work plays a supporting role. The most useful marker is NT-proBNP, a protein released when heart muscle is under strain. In pulmonary hypertension, the right side of the heart works harder than it should, and NT-proBNP levels rise in proportion to that strain. Levels below 300 ng/L are considered low risk. Between 300 and 1,400 ng/L signals intermediate risk. Above 1,400 ng/L indicates the heart is under significant stress. These numbers don’t diagnose pulmonary hypertension by themselves, but they help gauge severity and track how well treatment is working over time.
Other blood tests screen for conditions that can cause or accompany pulmonary hypertension: autoimmune markers for connective tissue diseases like scleroderma, liver function tests for portal hypertension, thyroid panels, and HIV testing. These help narrow down which of the five clinical groups you fall into.
The Six-Minute Walk Test
This deceptively simple test measures how far you can walk on a flat surface in six minutes. It captures your real-world exercise capacity in a way that lab numbers cannot. Registry data from multiple countries show that the average distance for people with pulmonary arterial hypertension falls between 329 and 378 meters, with higher distances in those who have milder symptoms. Walking more than 500 meters generally signals a better prognosis, while less than 300 meters points to more advanced disease.
You’ll typically do this test at diagnosis and again every few months to monitor your response to treatment. It’s also repeated whenever symptoms change. The distance you cover, combined with your biomarker levels and functional symptoms, feeds into a risk score that guides treatment decisions.
Lung Function and Imaging Tests
Pulmonary function tests measure how well your lungs move air and transfer oxygen into your blood. The most telling measurement for pulmonary hypertension is called the diffusing capacity, which reflects how efficiently oxygen crosses from your lung tissue into your bloodstream. A low diffusing capacity, particularly below 32% of the predicted normal value, is associated with worse outcomes and helps identify people whose pulmonary hypertension is driven by underlying lung disease.
A ventilation-perfusion scan (V/Q scan) is a specific imaging test used to check whether old blood clots in the lungs are causing the high pressure, a condition known as chronic thromboembolic pulmonary hypertension (CTEPH). This scan is preferred over a standard CT angiogram for this purpose because it catches roughly 96 to 97% of CTEPH cases, compared to only about 51% with CT. It also uses less radiation and avoids intravenous contrast dye. A normal V/Q scan effectively rules out CTEPH.
CT scans of the chest and sometimes cardiac MRI are still useful for looking at the lung tissue, the size of the pulmonary arteries, and the structure of the heart in more detail. They just aren’t the best tool for the specific question of chronic clots.
Right Heart Catheterization: The Definitive Test
No matter how strongly an echocardiogram suggests pulmonary hypertension, a right heart catheterization is required to confirm the diagnosis. During this procedure, a thin, flexible catheter is guided through a vein (usually in the neck or groin) into the right side of the heart and into the pulmonary artery. It directly measures the pressures that the echocardiogram can only estimate.
The three numbers that matter most are the mean pulmonary arterial pressure (mPAP), the wedge pressure, and the pulmonary vascular resistance. As of the 2022 guidelines, an mPAP above 20 mmHg confirms pulmonary hypertension. The wedge pressure distinguishes between two fundamentally different types. If it’s 15 mmHg or below, the problem originates in the pulmonary arteries themselves (pre-capillary). If it’s above 15 mmHg, the elevated pressure is being driven by problems on the left side of the heart (post-capillary), such as heart failure or valve disease. Pulmonary vascular resistance above 2 Wood units confirms a significant component of arterial disease.
These distinctions are not academic. Pre-capillary pulmonary hypertension can be treated with medications that relax the pulmonary arteries. Post-capillary pulmonary hypertension caused by left heart disease requires treating the underlying heart condition instead, and giving pulmonary vasodilators can actually make things worse.
Vasoreactivity Testing
For people diagnosed with pulmonary arterial hypertension (Group 1), the catheterization usually includes one additional step: a vasoreactivity test. While the catheter is still in place, you inhale or receive a short-acting drug that relaxes blood vessels. The goal is to see whether your pulmonary arteries respond dramatically. A positive response is defined as a drop in mean pulmonary pressure of at least 10 mmHg, reaching a level at or below 40 mmHg, without a drop in the heart’s output.
Only about 10 to 15% of patients with pulmonary arterial hypertension test positive, but for those who do, it opens the door to treatment with calcium channel blockers, a simpler and less expensive therapy. Patients who respond well to these medications can have significantly better long-term outcomes.
Classifying the Type of Pulmonary Hypertension
Once the catheterization confirms elevated pressures, all of the test results are assembled to place you into one of five clinical groups defined by the World Health Organization:
- Group 1: Pulmonary arterial hypertension (PAH). The small arteries in the lungs are narrowed and stiffened. This can be inherited, linked to connective tissue diseases, or have no identifiable cause.
- Group 2: Left heart disease. The most common cause overall. Heart failure or valve problems on the left side back up pressure into the lungs.
- Group 3: Lung disease or chronic low oxygen. Conditions like COPD, interstitial lung disease, or sleep apnea damage the lung’s blood vessels over time.
- Group 4: Chronic blood clots (CTEPH). Old clots that didn’t fully dissolve block or narrow the pulmonary arteries. This is the only form that can potentially be cured through surgery.
- Group 5: Unclear or multiple mechanisms. A catch-all for conditions like sarcoidosis or blood disorders where the cause doesn’t fit neatly into the other categories.
Getting the group right is the entire point of the diagnostic workup. Each group responds to different treatments, and misclassification can lead to therapies that are ineffective or harmful. This is why guidelines recommend that the final diagnosis and treatment plan happen at a specialized pulmonary hypertension center, where the team has experience interpreting the full constellation of tests together.