Diagnosing pulmonary arterial hypertension (PAH) can be difficult. PAH includes pulmonary hypertension that’s inherited or of unknown origin; it also includes cases of pulmonary hypertension linked to congenital heart disease, HIV, the uses of certain diet or street drugs (such as cocaine), and thyroid disorders. Like other types of pulmonary hypertension, it’s marked by a mean pulmonary arterial pressure greater than 25 mmHg at rest and greater than 30 mmHg during exercise.

Early symptoms, such as shortness of breath or fatigue, resemble those of many other conditions. Even a routine medical examination may not reveal the first stages of the disease, which is marked by abnormally high blood pressure in the arteries that supply the lungs with blood. As a result, PAH is frequently advanced by the time it is detected.

When doctors suspect pulmonary arterial hypertension, they begin by taking a careful medical history. Doctors typically ask about symptoms like fatigue, shortness of breath, chest pain, or fainting spells. They also discuss previous medical conditions, drug use, and family history of disease. A physical exam done in a doctor's office can also provide important clues. Doctors inspect the jugular vein in the neck for increased pressure, for instance. There are also telltale heart sounds doctors can detect through a stethoscope that suggest pulmonary hypertension. They may note enlargement of the liver or swelling of the legs or feet, all of which suggest advanced PAH.

Typically, since the symptoms and physical signs of pulmonary arterial hypertension are not specific to any disease, physicians would generally order an ECG (electrocardiogram) and chest X-ray for further evaluation of the findings. If the chest X-ray or ECG doesn't turn up another unrelated disorder (such as heart attack, a heart rhythm problem, or pneumonia), and the clinician continued to suspect pulmonary hypertension, he or she would next order an echocardiogram. The "echo," as it is called, is the most useful screening test pulmonary hypertension. If the "echo" showed evidence of PH, they would then try to determine the underlying cause of the disease with further testing.

Here are the first steps in the orderly diagnosis of pulmonary arterial hypertension and other types of PH:

•Chest x-ray. This simple and noninvasive test is used to see if the pulmonary arteries appear to be enlarged.

•Electrocardiogram (ECG). This test records the electrical activity produced by the beating of the heart. An ECG is performed by placing electrodes on the skin around the heart. Some ECGs are performed when patients are lying still. Others are done while a patient walks or runs on a treadmill. This test, called a stress test, shows how the heart performs during physical exertion. An ECG that shows problems with the chambers on the right side of the heart may indicate pulmonary arterial hypertension.

•Echocardiogram (commonly referred to as an "Echo"). This painless, noninvasive test uses sound waves to map the structure of the heart. It is the most useful screening test for PAH and other types of pulmonary hypertension. A small, microphonelike device is placed on a patient's chest. The device produces sound waves that create a moving picture of the heart at work. These sound waves can be used to estimate pulmonary blood pressure. An echocardiogram also produces still images that doctors study to gauge the size of the heart and thickness of the heart muscle. Pictures that show abnormally enlarged right chambers in the heart are an indication of pulmonary hypertension.

When doctors identify pulmonary hypertension on the "Echo," they first try to discover if there are any underlying causes. If so, it is much easier to treat. Doctors diagnose pulmonary arterial hypertension when tests show that blood pressure in the pulmonary artery is abnormally high but there is no evidence of other conditions that might explain it.

A wide range of tests are available to help experts further evaluate different types of pulmonary hypertension. Each provides specific information. Doctors frequently do several tests in order to get a full picture of a patient's condition. The most commonly performed procedures include:

•Blood Tests. Abnormal liver tests might suggest that the cause of the pulmonary hypertension (but not PAH) is cirrhosis. A tendency to form blood clots might be recognized on routine blood tests like prothrombin time (PT) or partial thromboplastic time (PTT). HIV testing should be considered in all patients with pulmonary hypertension. Tests for autoimmune disease should also be considered if a patient's history or examination suggests such a problem.

•Resting, exercise, and nocturnal oxygen assessments. Low oxygen levels are known to increase pulmonary artery pressure. Your doctor may want to check oxygen levels with a pulse oximeter while resting, walking, and/or sleeping. This device fits on your finger and indirectly measures how much oxygen is in your blood by using light beams. For an exact measurement, the doctor may order an arterial blood gas test. This procedure requires that a health provider insert a needle into your radial artery, which is located in the wrist, and take a blood sample. Although it is somewhat uncomfortable, it is more accurate than pulse oximetry.

•Pulmonary function tests. These tests help doctors assess whether there is a mechanical problem with the lung, such as emphysema or pulmonary fibrosis, which could explain pulmonary hypertension. (This would rule out pulmonary arterial hypertension, however, which is not generally caused by a lung disorder.) Patients breathe in and out through a mouthpiece while wearing a nose clip to shut off air flow through their nostrils. Each breath displaces air held in a container suspended in water. The rising and falling of the container produces a record, called a spirometer reading, which shows air flow in and out of the lungs and how much air the lungs hold. This test is most useful for determining if a mechanical lung problem has caused the pulmonary hypertension.

•Perfusion lung scan. For this test, doctors inject a harmless amount of radioactive substance into a vein. The substance enables doctors to trace blood flow in the lungs. Areas in the lung where blood flow is restricted show up as blank or clear areas. If the pulmonary hypertension is being caused by blood clots in the lungs, the test may show a scattering of blank or clear spaces. Not all pulmonary hypertension is caused by blood clots, however. A normal reading indicates that the problem may have another cause.

•Cardiac catheterization. This test involves the insertion of a very thin, flexible tube, called a catheter, into the right ventricle and pulmonary artery. The catheter is typically inserted through an artery in the arm, leg, or neck and then carefully guided into the heart. A right-heart cardiac catheterization allows doctors to precisely measure blood pressure in the right side of the heart and the pulmonary artery. It is the only test that directly measures the pulmonary blood pressure and is considered the most accurate. The test can also measure the amount of blood pumped out of the right side of the heart with each heartbeat. Cardiac catheterization can be performed only in a hospital by specialists.

•Chest computed tomography. A chest CT scan is sometimes performed to obtain an image of the condition of the lungs. It may indicate that subtle forms of scarring, previously undetected, have caused secondary pulmonary hypertension. It may also show blood clots in the pulmonary arteries.

•Pulmonary angiography. If a perfusion scan or CT scan shows evidence of blood clots, doctors often perform a pulmonary angiography. A catheter is inserted through a vein and threaded into the heart. Dye is then squirted through the catheter into the pulmonary arteries and X-ray images are taken. The images it provides can show the extent of blood clots and help doctors decide whether they can be treated surgically. Like a cardiac catheterization, this test is performed only by specialists in a hospital.

In addition to these commonly used tests, researchers are investigating other approaches that could help doctors diagnose and monitor the disease. One promising technique may require only a simple blood test. Researchers at the University of Colorado School of Medicine's Division of Pulmonary Sciences and Critical Care Medicine reported that patients with pulmonary arterial hypertension have abnormally high levels of endothelial cells in their blood. That finding makes sense: Endothelial cells are the cells that line the inner walls of arteries. These are the cells that begin to proliferate abnormally with pulmonary hypertension, causing the stiffening of arteries. Some of these abnormal cells break loose and circulate in the blood. Researchers hope they may eventually be able to follow the progress of the disease more precisely by measuring the level of these cells in the blood.

In addition, the discovery of a gene linked to pulmonary arterial hypertension represents a big step in understanding what causes the disease. However, even if a child inherits the abnormal gene, the likelihood of developing familial pulmonary hypertension is only about 20 percent. Because of this, and because medical screening recommendations remain the same for those with the gene, at this stage most experts advise against genetic tests to identify the gene. Researchers still have much to learn about how the presence of this gene interacts with other factors to cause the disease.

If you have been diagnosed with pulmonary hypertension, your doctor is likely to recommend that some of the more common tests be performed from time to time. Tests such as the echocardiogram or 6-minute walk tests (the distance you can walk in six minutes) are used to monitor your condition and the progress of the disease. If you have any questions about how a test is done or why it has been prescribed, ask your doctor.

-- Peter Jaret is a contributing editor for Health magazine and a winner of the American Medical Association's award for medical reporting. His work has appeared in National Geographic, Newsweek, Hippocrates, and many other national magazines. He is also the author of In Self-Defense (Harcourt Brace Jovanovich), Active Living Every Day, and Heart Healthy for Life.

References

The Rush Heart Institute Center for Pulmonary Heart Disease, www.rush.edu

Last updated November 25, 2008
Copyright © 2003 Consumer Health Interactive

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