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Diagnostic Tests

How is the pulmonary arterial pressure measured?

There are two main methods used to measure pulmonary artery (PA) pressures: trans-thoracic echocardiogram (TTE) and right heart catheterization.


An echocardiogram is an ultrasound of the heart; trans-thoracic means that the ultrasound probe rests on the outside of the chest (or "thorax"). Nothing is inserted into the body, so this test is called "non-invasive" and can be performed on an outpatient basis.


How does the echocardiogram measure your PA pressures if it is looking at the heart? Both the right ventricle and the beginning of the pulmonary arteries can be seen on the TTE. The TTE looks at the right ventricle as it pumps blood into the pulmonary arteries. Some of the blood from the right ventricle, instead of going forward into the pulmonary arteries, naturally leaks back into the right atrium via the tricuspid valve (see heart diagram). When PA pressures are higher than they should be, it is harder for the right ventricle to pump blood forward and more of it therefore leaks back through the tricuspid valve. The TTE can measure the amount of leakage (or regurgitation) and use that to estimate the PA pressure. In some patients, PAH is seen only with exercise. In these cases, a TTE can be done to measure PA pressure after an exercise test (such as walking on a treadmill).


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In contrast to the indirect measurement obtained by TTE, a right heart catheterization is a more invasive test that requires the placement of a pressure monitor directly into the pulmonary arteries. This technique allows for direct measurement of the systolic and diastolic PA pressures, and thus often results in more accurate measurements. However, because the right heart catheter is an invasive procedure, you will not have this done every time your doctor wishes to check your PA pressures.


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