Six Minute Walk
A six-minute walk (sometimes referred to as 6MW) test is as its name suggests: a walk for exactly six minutes. During these 6 minutes, the patient’s heart rate and oxygen level (measured by a non-invasive monitor typically placed on one’s finger, called “pulse oximeter”) are recorded at the beginning of the 6MW test and then again at the end of the 6 minutes. The distance walked is also recorded. This is an extremely important test to check the functional ability of patients with pulmonary hypertension, and to assess the need for oxygen therapy. This non-invasive test is typically done on every single clinic visit for patients with pulmonary hypertension.
Heart catheterization is the gold standard for confirming the diagnosis of pulmonary hypertension and quantifying its severity. It is an invasive procedure whereby a physician introduces a catheter (which a narrow plastic tube) into a vein under full sterile measures. This catheter is then advanced towards the heart. There are 2 major kinds of heart catheterizations, a “left heart catheterization” and a “right heart catheterization”:
- Left heart catheterizations are often done looking for “blockages” in the heart vessels. Patients who are at risk of heart attacks would typically get a left heart catheterization. Heart stents for example are done during left heart catheterizations. Contrast is a “colored” material or ‘tracer’ that shows up on X-rays and is commonly used for left heart catheterization. Right heart catheterizations do not typically require injection of contrast.
- Right heart catheterizations are an invasive procedure typically done in the outpatient setting, and it is the only way to diagnose pulmonary arterial hypertension at this time. Every patient with suspected pulmonary hypertension must have a right heart catheterization before deciding on pulmonary hypertension therapy.
Most patients with pulmonary hypertension do not really need a left heart catheterization. Patients with suspected pulmonary hypertension need what’s called a right heart catheterization which is the kind of heart catheterization during which the catheter is advanced through the right side of the heart to measure pressures on the right side of the heart and in a large blood vessel called the “Pulmonary Artery”. The pulmonary artery is the vessel that connects the right side of the heart to the lungs.
The Ventilation/Perfusion scan (also called a V/Q scan) looks for blood clots in the lungs. A V/Q scan is 2 tests combined into one. The ‘V’ stands for ventilation part of the test, and the ‘Q’ stands for the perfusion part of the test. This test involves exposure to a very small amount of radiation that is believed to be in the safe range as long as this test is not done too often. Typically this test is done once during the evaluation of a patient with pulmonary hypertension, and only rarely needs to be repeated. Almost all patients with pulmonary hypertension should have a V/Q scan test done to make sure that their pulmonary hypertension is not caused by blood clots. The treatment of pulmonary hypertension that is caused by chronic blood clots in the lungs is different from pulmonary hypertension caused by other reasons. A CT scan is not adequate to exclude this cause of pulmonary hypertension.
- During the ventilation part of the test (the ‘V’ part), a patient is asked to breath a safe gas that has in it a “tracer” that shows up on Xray. This test shows which parts of the lung are getting air into them.
- The perfusion part of the test (the ‘Q’ part) is very similar but the tracer is given through an intravenous catheter (an “IV”), and it also shows up on an X-ray to show where the blood is going to in the lungs.
- Blood clots would be suspected if certain areas of the lungs are getting air (as shown on the ventilation part of the test) but that same lung area is not getting blood (as shown on the perfusion part of the test).
This concludes our 4 part Series on Pulmonary Hypertension. Click here for more information Info
One of the causes of pulmonary hypertension is poor quality breathing during sleep. If someone’s oxygen levels are low during sleep, this condition puts a lot of strain on the lungs and heart and may lead to pulmonary hypertension. Since a patient would be asleep when these abnormalities of breathing are occurring, she/he may not feel that their breathing is limited during sleep and may not be aware of this.
- A sleep study is a study done in a sleep center (which is typically not a hospital). The patients come to the sleep center in the evening, get hooked up to different monitors including an oxygen monitor and are asked to sleep (most patients’ first reaction is that they won’t be able to sleep in a “strange environment” other than their own bed, & hooked up to different monitors. But most patients end up sleeping enough to give us the data needed). When they wake up in the morning, they go back home. If a patient indeed has trouble with her/his breathing when asleep, they may need to be on oxygen or use certain masks, such as a CPAP (continuous positive airway pressure), at night to help with their breathing and to improve their pulmonary hypertension.
- An overnight oximetry study is a test in which a recording “pulse oximeter monitor” (a small non-invasive machine with a probe that is taped to the finger) continuously measures a patient’s oxygen level and heart rate overnight. This test could be done in someone’s home. This is more convenient than the sleep study but does not give us all the information needed.
An EKG is a non-invasive test that measures the electricity of the heart. It involves placing what is called ‘leads’ on the chest, arms, and legs. The patient does not feel any electricity or discomfort during this test. The EKG provides information about how fast and regular the heart is beating and gives us a general sense about the global function of the different parts of the heart, which in turn need to be confirmed by an echocardiogram.
The echocardiogram (sometimes referred to as the “echo“) is a non-invasive ultrasound test of the heart that does not involve any radiation. It is very safe to have echocardiograms. The ultrasound technician would be using gel (which may sometimes feel cold) on an ultrasound probe that is connected to the ultrasound machine. That machine has a screen similar to a desktop computer screen. Multiple images are recorded during this test.
The echo test is extremely important because it gives us a general idea about the size and function and interaction of the different heart chambers. It can also assess the function of the different heart valves. An echocardiogram is done on every patient who is suspected to have pulmonary hypertension, and then on a regular basis after the diagnosis is made.
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A Chest X-Ray, sometimes referred to as CXR, is usually one of the first tests done on patients who have some trouble with their breathing. The Chest X-ray takes a picture or two of the chest, which would show any gross abnormalities in the lungs.
Sometimes, a Chest X-ray is not sensitive enough to find subtle or small abnormalities in the chest, so a CT (computed tomography scan, sometimes referred to as “CAT scan” or “CT scan”) is needed. A CT scan is a much more detailed and refined X-Ray but with higher exposure to radiation. If the CT scan is not done too often, the extent of radiation exposure from a CT scan is not dangerous.
Pulmonary function tests, also called PFTs, are a set of non-invasive tests that measure different aspects of a patient’s breathing. This is a very important test for patients who have trouble with their breathing. The information from this test may show different causes of someone’s trouble breathing, including for example asthma, COPD, emphysema, or “pulmonary fibrosis” / lung scarring. Pulmonary hypertension has a specific abnormal pattern on PFTs. PFTs include multiple different tests:
- Spirometry measures how fast a patient can breathe out. Patients with asthma or COPD for example can’t breathe out too fast because of limitations in their airways. Patients with pulmonary hypertension should not have a problem with their airways, so their spirometry test is usually normal or close to normal.
- Lung volumes measure the lung ability in total to breathe in and out, and may reflect how “restricted” a patient’s breathing is.
- Diffusion capacity (also called DLCO) reflects the extent of the damage to the blood vessels in the lungs. It may also reflect any scarring that is going on in the lungs. It is a measure of how well oxygen can get across the lung to the blood vessels.
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