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Diagnostic Tests

Why do I need so many tests?

Initially, most PAH patients have a number of tests to identify the cause of their symptoms. Symptoms that are non-specific, such as shortness of breath or chest discomfort, often require many tests before the exact problem is identified. Since PAH is rare compared to common disorders, such as asthma, it is typical for patients to get tested for other lung problems first.

Once pulmonary hypertension has been identified (typically by an echocardiogram which provides an estimate of the pulmonary pressures), further testing is done with three goals in mind.

The first goal of testing is to understand what, if anything specifically, is causing the pulmonary hypertension. A series of blood tests is usually done looking for disorders like scleroderma, lupus, rheumatoid arthritis and other collagen-vascular diseases. Additional blood tests are done for HIV infection and liver disease, such as cirrhosis or hepatitis. Pulmonary function tests may be done to measure your breathing capacity and the ability of your lungs to exchange oxygen and carbon dioxide (called the diffusing capacity). X-rays of your chest may be obtained to look for lung disease (particularly if you are a former smoker), and advanced imaging studies including CAT scans and a nuclear medicine scan called a ventilation-perfusion lung scan will likely be obtained to ensure that you haven't had multiple blood clots in your lungs.

Common sleep disorders, such as obstructive sleep apnea, can also cause moderate pulmonary hypertension, so your physician may arrange for an overnight test of your sleep called polysomnography. Certain congenital heart defects (typically involving a hole in the wall separating the left and right atria) may also lead to pulmonary hypertension, and your doctor may look for this cause by obtaining an echocardiogram that involves insertion of small amounts of agitated (stirred up) saline inserted through a vein in your arm. This is called an echocardiogram with bubbles or a "bubble study." If a hole in the atrial septum exists, the bubbles can usually be seen passing through.

The second goal of testing is to determine the severity of the pulmonary hypertension by looking at the pulmonary arterial pressure. While an echocardiogram is a non-invasive test, it only provides an indirect estimate of the pulmonary pressures based on complex formulas involving measurements obtained with the ultrasound. In contrast, cardiac catheterization directly measures the exact pressures and determines the amount of blood that the heart can pump. This is an invasive test which typically requires several hours at the hospital.

The final goal is to determine your functional level, meaning how much physical activity you are able to perform. Your doctor may have you walk back and forth in a hallway with an oxygen saturation monitor on your finger. This test is called exercise oximetry. A more complex version of this test is called the 6 minute walk test. During this test, you will have 6 minutes to walk as far and as fast as you can (you are not allowed to run even if you are able to). The distance you walk is measured, along with your blood pressure, heart rate, respiratory rate, oxygen saturation, and symptoms of breathlessness. Exercise stress tests may also be done either on a bicycle or a treadmill to determine your exercise capacity. Six minute walk tests are well correlated with the results of formal exercise tests, and are easier and quicker to perform and hence these are used more frequently to monitor this disorder.