Pulmonary hypertension is diagnosed through a combination of noninvasive tests followed by a definitive procedure called right heart catheterization, which directly measures the pressure inside your pulmonary arteries. A diagnosis is confirmed when the mean pulmonary arterial pressure (mPAP) exceeds 20 mmHg at rest. Because several different conditions can cause elevated lung pressure, the diagnostic process also involves identifying the underlying cause, which shapes treatment.
Symptoms That Prompt Testing
Pulmonary hypertension develops gradually, and early symptoms overlap with many other conditions. Unexplained shortness of breath during routine activity is the most common reason people end up being evaluated. Fatigue, chest tightness, dizziness, and swelling in the ankles or legs can also raise suspicion, especially when they worsen over time without a clear explanation.
Blood Tests and EKG
A blood test measuring a protein called NT-proBNP is one of the first steps. Your heart produces this protein in larger amounts when it has to work harder than normal to pump blood. Elevated levels don’t confirm pulmonary hypertension on their own, but they signal that the heart is under strain and warrant further investigation.
An electrocardiogram (EKG) can reveal patterns of right heart strain that point toward pulmonary hypertension. Right axis deviation, which reflects the right side of the heart working harder, has a predictive value of 93% in adults with suspected pulmonary hypertension. Another telling sign is an unusually tall P wave on the tracing, called P pulmonale, which indicates the right atrium is enlarged. These findings aren’t enough for a diagnosis, but they help doctors decide whether to order more detailed imaging.
Echocardiogram: The Key Screening Test
An echocardiogram, a type of ultrasound of the heart, is the primary noninvasive screening tool. It estimates the pressure in your pulmonary arteries by measuring how fast blood leaks backward through the tricuspid valve (the valve between the right atrium and right ventricle). This backward flow, called tricuspid regurgitation, is present to some degree in most people, and its speed lets doctors calculate the estimated systolic pressure in the right ventricle.
An estimated right ventricular systolic pressure above 37 mmHg raises concern for pulmonary hypertension. The echocardiogram also looks at the size and function of the right ventricle, the diameter of the inferior vena cava (the large vein returning blood to the heart), and how much that vein collapses when you breathe in. A vein wider than 2.1 cm that collapses less than 50% with inspiration suggests elevated right-sided pressures.
While echocardiograms are excellent for screening, they provide estimates rather than exact measurements. Pressures can be over- or underestimated depending on image quality and the degree of tricuspid regurgitation present. That’s why a suspicious echocardiogram leads to catheterization rather than a final diagnosis.
Right Heart Catheterization: The Definitive Test
Right heart catheterization is the gold standard for diagnosing pulmonary hypertension. During this procedure, a thin, flexible tube is inserted through a vein, typically in the neck or groin, and threaded through the right side of the heart into the pulmonary artery. It directly measures pressure and blood flow in real time.
Three key numbers determine the diagnosis and its type:
- Mean pulmonary arterial pressure (mPAP): Must be above 20 mmHg for any pulmonary hypertension diagnosis.
- Pulmonary arterial wedge pressure (PAWP): Reflects pressure on the left side of the heart. A PAWP of 15 mmHg or below, combined with elevated mPAP, indicates the problem originates in the lung arteries themselves (pre-capillary pulmonary hypertension). A PAWP above 15 mmHg suggests the elevated pressure is being driven by left heart disease.
- Pulmonary vascular resistance (PVR): Calculated from the other measurements. A PVR above 2 Wood units confirms significant resistance in the lung blood vessels.
These numbers together determine which hemodynamic category you fall into. Pre-capillary pulmonary hypertension (high mPAP, normal PAWP, elevated PVR) includes the most classic forms of the disease. Post-capillary pulmonary hypertension (high mPAP and high PAWP) is driven by problems on the left side of the heart. Some patients have a combination of both.
Identifying the Underlying Cause
Once elevated pressures are confirmed, doctors need to figure out why. Pulmonary hypertension is classified into five groups based on the underlying mechanism, and each group has different treatment options. Several additional tests help sort this out.
V/Q Scan for Blood Clots
A ventilation/perfusion (V/Q) scan is a standard part of the workup because it’s the best way to check for chronic thromboembolic pulmonary hypertension, a form caused by old blood clots that never fully dissolved in the lung arteries. This type is important to identify because it can sometimes be treated with surgery. The V/Q scan is more sensitive for detecting these clots than a CT scan. A diagnosis requires at least one defect covering half a lung segment or more, present after at least three months of blood thinner treatment.
Lung Function and Sleep Studies
Pulmonary function tests help determine whether chronic lung diseases like COPD or pulmonary fibrosis are contributing to elevated pressures. Overnight sleep studies can identify sleep apnea, another common contributor. These conditions fall into their own classification group and are managed differently from pulmonary arterial hypertension.
Cardiac MRI
Cardiac MRI is considered the gold standard for evaluating the right ventricle’s size, mass, and pumping ability. It provides precise measurements of how much blood the right ventricle ejects with each beat (ejection fraction) and how much the chamber has enlarged or thickened in response to high pressures. This information helps gauge severity and track changes over time, though it’s not used in every patient.
Autoimmune and Liver Screening
Blood tests for connective tissue diseases like scleroderma and lupus are routine because these conditions are common causes of pulmonary arterial hypertension. Liver disease with portal hypertension can also drive elevated lung pressures, so liver function and imaging may be part of the evaluation.
Assessing Functional Severity
Beyond confirming the diagnosis, doctors assess how much the condition limits your daily life. The six-minute walk test is one of the simplest and most widely used tools. You walk back and forth along a corridor at your own pace for six minutes, covering as much distance as you can. You’re allowed to stop and rest if needed. The total distance, combined with changes in heart rate and oxygen levels, gives a practical snapshot of your exercise capacity.
Patients are also assigned a functional class from I to IV, similar to heart failure grading. Class I means no symptoms during ordinary activity. Class II involves mild limitation with exertion. Class III means significant limitation where even light activity causes symptoms. Class IV indicates symptoms at rest. This functional class influences treatment decisions and helps track whether the disease is stable, improving, or progressing.
Why the Process Takes Multiple Steps
The layered diagnostic approach exists because pulmonary hypertension is not a single disease. It’s a hemodynamic state with dozens of possible causes, and identifying the right cause changes the treatment entirely. Someone with pulmonary hypertension from left heart failure needs a completely different approach than someone with pulmonary arterial hypertension from an autoimmune disease. The combination of pressure measurements, imaging, and targeted blood work narrows the picture until doctors can assign a specific group and start appropriate therapy.