The PAH medical abbreviation usually stands for pulmonary arterial hypertension, a condition in which the small arteries of the lungs become narrowed and the blood pressure inside them rises. That extra pressure makes the right side of the heart work harder over time.
PAH also has a few other meanings that turn up in specific settings. In kidney physiology it stands for para-aminohippurate, a substance once used to measure blood flow to the kidneys. In genetics it names the phenylalanine hydroxylase gene linked to phenylketonuria. Context almost always settles which one a note means, and this page walks through each with sample lines.
At a glance
Stands for
Pulmonary arterial hypertension (most common)Other meanings
Para-aminohippurate (kidney); phenylalanine hydroxylase (genetics)Where you see it
Cardiology and lung clinic notes, echo reports, physiology coursesConfirmed by
Right heart catheterizationDo not confuse with
PH (pulmonary hypertension of any cause) and PAD (peripheral artery disease)Specialty
Pulmonology, cardiology, nephrology
What the PAH medical abbreviation means in heart and lung care
Pulmonary arterial hypertension is a specific type of high blood pressure in the lungs. The walls of the small pulmonary arteries thicken and stiffen, so blood has a harder time passing through. The right ventricle, which pumps blood into the lungs, has to push against more resistance and can weaken over time.
Common symptoms include shortness of breath with activity, tiredness, chest discomfort, fainting and swelling of the ankles. PAH can be inherited, linked to certain medicines or toxins, connected to other conditions such as connective tissue disease, or have no known cause. Normal resting pressure in the pulmonary artery is much lower than in the arm, and labs and centers set their own exact cutoffs.
PAH versus PH: why the extra letter matters
Pulmonary hypertension, written PH, is the broad term for high pressure in the lung circulation from any cause. Doctors sort it into five groups. PAH is Group 1, the type that starts in the small lung arteries themselves. Other groups come from left heart disease, lung disease or low oxygen, blood clots in the lungs, and mixed causes.
| Group | Main cause |
|---|---|
| 1 | PAH, disease of the small pulmonary arteries |
| 2 | Left heart disease, such as HFpEF |
| 3 | Lung disease or low oxygen, such as COPD or sleep apnea |
| 4 | Chronic blood clots in the lung arteries |
| 5 | Unclear or multiple causes |
The difference matters because treatment for Group 1 differs from treatment aimed at heart or lung disease.
How PAH shows up in notes and reports
An echocardiogram, written TTE, can estimate lung pressures and suggest the diagnosis, but a right heart catheterization measures them directly and confirms it.
On an echo report: "Estimated RVSP 65 mmHg, RV dilated, concern for PAH, recommend RHC." RVSP is the estimated pressure in the right ventricle, RV is the right ventricle, and RHC means right heart catheterization.
In a clinic note: "PAH, functional class II, stable on ambrisentan and tadalafil." Functional class describes how much daily activity is limited, and the two generic drug names are examples of medicines used in this condition.
PAH medical abbreviation in kidney physiology
Students in physiology and nephrology meet PAH as para-aminohippurate, sometimes called para-aminohippuric acid. The kidneys filter and secrete it so efficiently that nearly all of it is removed from the blood in one pass. Measuring how fast it is cleared therefore gives an estimate of effective renal plasma flow, the amount of plasma flowing through the kidneys.
PAH clearance is mainly a teaching and research tool today. Routine kidney function is tracked with blood tests such as creatinine and an estimated GFR. Seeing PAH in a kidney lecture or an exam question about renal clearance almost always means this substance, not lung disease.
Other places the letters appear
In genetics, PAH is the symbol for the phenylalanine hydroxylase gene and enzyme. Changes in this gene cause phenylketonuria, which newborn screening looks for. In environmental health, PAHs are polycyclic aromatic hydrocarbons, chemicals formed when fuel, wood or food is burned. Both are written in very different settings from a heart or lung note, so mix-ups are rare when the context is read.
Lung, heart and many other diagnoses are listed in the condition abbreviations hub.
Questions worth raising with the care team
- Is this pulmonary hypertension in general, or PAH specifically?
- Was the diagnosis confirmed by right heart catheterization?
- What functional class am I in, and what does it mean for daily activity?
- Which follow-up tests will track how things are going?
This page explains what the letters stand for, not how any one person should be treated. A lung or heart specialist can explain what a PAH diagnosis means in your own situation.
Frequently asked questions
What is PAH short for in a medical record?
Most often PAH stands for pulmonary arterial hypertension, high blood pressure in the small arteries of the lungs. In kidney physiology it stands for para-aminohippurate, and in genetics for the phenylalanine hydroxylase gene.
What does PAH mean in kidney tests?
In kidney physiology, PAH means para-aminohippurate. Its clearance is used to estimate effective renal plasma flow, mostly in research and teaching rather than routine care.
Is PAH the same as pulmonary hypertension?
PAH is one type of pulmonary hypertension. PH is the broad term, and PAH is Group 1, where the disease starts in the small lung arteries themselves.
How is PAH diagnosed?
An echocardiogram can suggest it, but a right heart catheterization measures the pressures directly and confirms it. Other tests look for the underlying cause.
Is PAH the same as high blood pressure?
No. Ordinary high blood pressure, written HTN, refers to pressure in the arteries of the body. PAH refers to pressure in the arteries of the lungs, which is measured differently.