context: Pulmonary arterial hypertension ( PAH) is tough to diagnose. Its symptoms can seem vague, and they're also signs of many other problems that aren't as serious. Your doctor will most likely try to rule out other causes of your symptoms first. You may need to see a heart specialist, called a cardiologist, or a lung specialist, called a pulmonologist. Or your doctor may send you to a center that specializes in diagnosing and treating PAH. But once your doctor knows you have the condition and what's causing it, they can recommend a treatment that has the best chance of helping you. First you'll get a thorough one and talk about your medical history. Your doctor will want to know all of your symptoms, how long you've had them, and when you notice them. You should tell them about any other medical conditions you have and whether any of your family members have heart or lung problems. They'll listen to your heart and lungs and check for swelling in your legs and ankles and blueness in your lips or skin. Blood tests can show if your body is getting enough oxygen. They also show signs of other illnesses that could be causing your symptoms or causing the high blood pressure. Your doctor will probably test: How well your liver works How well your kidneys work How well your thyroid works If you have an autoimmune disorder If you have infections, including HIV The next step is to get a good picture of what's going on with your heart and lungs. Your doctor will look for anything unusual in the size and shape of your heart's chambers and arteries. They'll also look for masses in your chest or scarring in your lungs. Doctors use a few common imaging tests to look in your chest: Echocardiogram. A machine uses sound waves to make a picture of your heart. It can also estimate pressure inside your arteries. Chest X-ray Chest CT scan. A powerful X-ray makes detailed pictures inside your chest. MRI. Powerful magnets and radio waves make images of your heart. Other tests look specifically at your lungs and how well they are working. Lung function tests. These measure how well air flows into and out of your lungs and how much they can hold. It also measures how well they exchange carbon dioxide and oxygen. Lung ventilation/perfusion scan. This measures both air flow and blood flow in your lungs. It also reveals blood clots. Open- lung biopsy. Rarely, a doctor might recommend an open-lung biopsy. An open-lung biopsy is a type of surgery in which a small sample of tissue is removed from your lungs under general anesthesia to check for a possible secondary cause of pulmonary hypertension. A sleep study can show how much oxygen your body gets while you're not awake and whether you have sleep apnea. An electrocardiogram measures your heart's electrical activity and shows if your heartbeat is steady and regular. Genetic testing can show if you have PAH because of a gene flaw and whether your family members are more likely to get it. If your test results point to PAH, the best way to be sure you have it is with a procedure called a right heart catheterization. During the test, you'll be awake but heavily sedated. The doctor puts a thin tube, called a catheter, into a large artery either in your neck or groin. They thread the tube through your body to your heart, then into the vessel that goes from the heart's right side to your lungs, called the pulmonary artery. The catheter has a tiny balloon at the tip that's blown up until it touches the walls of the artery. Then it measures the pressure there. During that procedure, you may also have another test called a vasodilator study. The doctor gives you a drug that relaxes your blood vessels. If it lowers the pressure in your pulmonary artery, vasodilator drugs might be able to help treat your PAH. To see how severe your PAH is, your doctor needs to see your heart and lungs in action. They may order comprehensive tests to find the limits of exercise capacity and see if you need oxygen. It helps your doctor decide how much physical activity is safe for you. After you start treatment, you might take this test from time to time to see how well your plan is working.