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Diagnosis and Assessment of Pulmonary Arterial Hypertension
Pulmonary Arterial Hypertension (PAH) is rarely picked up in a routine medical examination. Even in its later stages, the signs of the disease can be confused with other conditions affecting the heart and lungs. Thus, much time can pass between the time the symptoms of PH appear and a definite diagnosis is made.
Idiopathic PAH is a diagnosis of exclusion. This means that it is diagnosed only after the doctor finds elevated blood pressure in the lungs and excludes or cannot find other reasons for the hypertension, such as a chronic pulmonary disease (chronic bronchitis, pulmonary fibrosis, emphysema etc.), blood clots in the lung (pulmonary thromboemboli), serious liver maladies or some forms of congenital heart disease. The first tests on the list below (non-invasive) help the doctor determine how well the heart and lungs are performing. If the results of these tests do not give the doctor enough information, the doctor should perform a cardiac catheterization (invasive). The procedure, discussed below, is one of the tools the doctor needs in order to make certain that the patient's problems are due to PAH and not to some other condition.
PAH also can exist as a secondary condition in people with lung disease, liver disease, wleep apnea or other heart irregularities. If a doctor determines PAH is present along with another disease or condition, the doctor should treat both the underlying disease and the PAH.
Source: National Heart, Lung, and Blood Institute, Division of Lung Diseases, Primary Pulmonary Hypertension
Tests used to Diagnose Pulmonary Hypertension:
Electrocardiogram
Echocardiogram
Pulmonary Function Tests
Perfusion Lung Scan
Right-Heart Cardiac Catheterization
Other Tests & Equipment You May Encounter
Summary
Categorizing the Severity of PAH:
Functional Classification
Electrocardiogram
The electrocargiogram (ECG) produces a record of the electrical activity produced by the heart. An abnormal ECG may indicate that the heart is undergoing unusual stress. In addition to the usual ECG performed while the patient is at rest, the doctor may order an exercise ECG. This ECG helps the doctor evaluate the performance of the heart during exercise, for example, walking a treadmill in the doctor's office.
Echocardiogram
In an echocardiogram, the doctor uses sound waves to map the structure of the heart by placing a slim device that looks like a microphone on the patient's chest. The instrument sends sound waves into the heart, which then are reflected back to form a moving image of the beating heart's structure on a TV screen. A record is made on paper or videotape. The moving pictures show how well the heart is functioning. The still pictures permit the doctor to measure the size of the heart and the thickness of the heart muscle; in the patient with severe pulmonary hypertension, the still pictures will show that the right heart is enlarged, while the left heart is either normal or reduced in size. Echocardiograms are helpful in excluding some other causes of pulmonary hypertension and can be useful in monitoring the response to treatment.
Pulmonary Function Tests
A variety of tests called pulmonary function tests (PFTs) evaluate lung function. In these procedures, the patient, with a nose clip in place, breathes in and out through a mouthpiece. The patient's breathing displaces the air held in a container suspended in water. As the container rises and falls in response to the patient's breathing, the movements produce a record, or spirogram, that helps the doctor measure lung volume (how much air the lungs hold) and the air flow in and out of the lungs. Some devices measure air flow electronically. A mild restriction in air movement is commonly seen in patients with PPH. This restriction is thought to be due, in part, to the increased stiffness of the lungs resulting from both the changes in the structure and the high blood pressure in the pulmonary arteries.
Perfusion Lung Scan
A perfusion lung scan shows the pattern of blood flow in the lungs; it can also tell the doctor whether a patient has large blood clots in the lungs. In the perfusion scan, the doctor injects a radioactive substance into a vein. Immediately after the injection, the chest is scanned for radioactivity. Areas in the lung where blood clots are blocking the flow of blood will show up as blank or clear areas. Two patterns of pulmonary perfusion are seen in patients with PPH. One is a normal pattern of blood distribution; the other shows a scattering of patchy abnormalities in blood flow. A variety of tests are needed to diagnose PPH. A major reason for doing a perfusion scan is to distinguish patients with PPH from those whose pulmonary hypertension is due to blood clots in the lungs.
Right-Heart Cardiac Catheterization
In right-heart cardiac catheterization, the doctor places a thin, flexible tube, or catheter, through an arm, leg, or neck vein in the patient, and then threads the catheter into the right ventricle and pulmonary artery. Most important in terms of PPH is the ability of the doctor to get a precise measure of the blood pressure in the right side of the heart and the pulmonary artery with this procedure. It is the only way to get this measure, and must be performed in the hospital by a specialist. During catheterization, the doctor can also evaluate the right heart's pumping ability; this is done by measuring the amount of blood pumped out of the right side of the heart with each heartbeat.
Other Tests & Equipment You May Encounter
Six Minute Walk
One of the simplest tests doctors often use to assess exercise tolerance, is the six-minute walk. Typically a technician will take your resting blood pressure, measure your blood saturation (by placing a little clip on your finger that is attached to a pulse oximeter) and then you will be asked to walk as quickly as you can without pausing or stopping while the technician watches the clock. This test is often conducted in a long inner hallway where the distances have been mapped. At the end of the six minutes, the technician will have you sit, your blood pressure and blood sats will again be taken and you will be asked to describe your shortness-of-breath. This test is repeated after diagnosis during your regular check-up appointments as it is a good way to monitor improvements or deterioration of your condition.
Pulse Oximetry
With any heart or lung disorder, there is the possibility that an adequate amount of oxygen may not be present in your bloodstream. Pulse oximetry is a simple non-invasive method of monitoring the percentage of haemoglobin (Hb) which is saturated with oxygen. The pulse oximeter consists of a probe attached to the patient's finger or ear lobe which is linked to a computerised unit. The unit displays the percentage of Hb saturated with oxygen together with an audible signal for each pulse beat, a calculated heart rate and in some models, a graphical display of the blood flow past the probe. Audible alarms which can be programmed by the user are provided. An oximeter detects hypoxia before the patient becomes clinically cyanosed.
How does an oximeter work? A source of light originates from the probe at two wavelengths (650nm and 805nm). The light is partly absorbed by haemoglobin, by amounts which differ depending on whether it is saturated or desaturated with oxygen. By calculating the absorption at the two wavelengths the processor can compute the proportion of haemoglobin which is oxygenated. The oximeter is dependant on a pulsatile flow and produces a graph of the quality of flow. Where flow is sluggish (eg hypovolaemia or vasoconstriction) the pulse oximeter may be unable to function. The computer within the oximeter is capable of distinguishing pulsatile flow from other more static signals (such as tissue or venous signals) to display only the arterial flow.
Summary
After your doctor has evaluated most or all of the above tests, you will be placed in a functional class. This is a way to categorize your level of impairment from PAH. When you hear your doctor talk about your pulmonary artery pressure, keep in mind that it does not tell the whole story. Doctors look at lung pressure, heart and lung function and exercise tolerance in total in making their assessment. That is why another patient with the same pulmonary artery pressure may fall into another functional class. There is more to it than PA alone.
We encourage you to be proactive in managing your disease, to go to your office visits with as much information as possible and to take an active role in advocating for yourself. You’ll find some very good advice about getting the most out of your doctor visits in WORKING WITH YOUR DOCTORS in our Tips & Tricks section.
Functional Classification
Once PPH is diagnosed, most doctors will classify the disease according to the functional classification system developed by the New York Heart Association. It is based on patient reports of how much activity they can comfortably undertake.
- Class 1 is assigned to patients with no symptoms of any kind, and for whom ordinary physical activity does not cause fatigue, palpitation, dyspnea, or anginal pain.
- Class 2 is assigned to patients who are comfortable at rest but have symptoms with ordinary physical activity.
- Class 3 is assigned to patients who are comfortable at rest but have symptoms with less-than-ordinary effort.
- Class 4 is assigned to patients who have symptoms at rest.
Much of the information on this page was provided by Lynn Schaefer, our medical editor who passed away in 2003. New information – six minute walk, pulse oximetry and summary – was added July 2006 from reputable online resources including a publication by Dr SJ Fearnley on Pulse Oximetry from the Department of Anaesthetics, Torbay Hospital, Torquay, UK.
Published in the July 2004 issue of CHEST, the peer-reviewed journal of The American College of Chest Physicians: Diagnosis and Management of Pulmonary Arterial Hypertension: ACCP Evidence-Based Clinical Practice Guidelines |
