Exercise (Stress) Tests for PAD

What is exercise testing?

An exercise test (also called a treadmill test) is a diagnostic test that measures blood flow in your arteries before and after you exercise. Exercise testing can diagnose PAD in the legs in women who have a normal Ankle-Brachial Index (ABI) at rest, but may still have PAD.

In some women, PAD symptoms are not apparent at rest and only show up when the legs need more blood than usual, such as during exercise. The exercise test measures the ability of your arteries to provide enough blood to your muscles when they are working hard (or stressed).

Who might have an exercise test?

An exercise test is used to diagnose PAD in women with a normal ABI at rest, but whose doctor still suspects she may have PAD. This may be because she experiences leg pain only during exercise, or because she has other PAD symptoms despite a normal ABI.1 An exercise test can determine if leg pain or fatigue during exercise is caused by PAD.

In women who have been diagnosed with PAD, an exercise test can evaluate how PAD is affecting their walking capacity and determine a safe level of exercise. This helps doctors develop a personalized treatment plan. All women with PAD should have an exercise test before starting a rehabilitation program that includes exercise. See Exercise & Lower Extremity PAD Rehabilitation (coming soon) for more.

The results of an exercise test give doctors a starting measurement of the severity of your PAD symptoms and your ability to exercise. Additional tests after you have received treatment for PAD can be compared to your earlier results to see how well the treatment is working.

Who should not have an exercise test?

You should not have a treadmill exercise test if you have very limited blood flow to your legs (pain at rest or sores on your feet). Women with symptoms caused by disease in the coronary arteries (such as chest pain), or who have severe aortic disease or very high blood pressure, should not have an exercise test because the exertion could cause further heart problems.

Because the exercise test uses an ABI to diagnose PAD, women who have a suspected blood clot in the veins of the legs (deep vein thrombosis, or DVT) should not have an exercise test. Squeezing of the leg during an ABI can cause the clot to break off and travel to the lungs, causing a potentially deadly pulmonary embolism. For this reason, an ultrasound should be used to rule out DVT before performing an exercise test in women with suspected blood clots in the veins.

How do I prepare for the test?

You should not smoke, eat, or drink anything other than water for 2 hours before a treadmill exercise test. Tell your doctor about any medications or dietary supplements you are taking because these may affect the accuracy of the test.

You should wear loose, comfortable clothing and shoes appropriate for exercising.

What happens during the test?

The exercise test may take place in your doctor’s office or in a vascular laboratory. Before you exercise, you will have an ABI test that measures how blood is flowing in your legs compared with your arms when you are at rest. These results will be compared to your ABI after you exercise. See our article on the Ankle-Brachial Index for details of how this test is performed.

The technologist will place a blood pressure cuff around your arm, and sticky pads may be placed on your chest and attached to an ECG machine to monitor your heart’s electrical activity during the test.

When you are ready, the exercise portion of the test will begin. You will walk on a motorized treadmill. The speed may be steady, or the treadmill may gradually move faster and become steeper to make sure you are working hard. You will be asked to report when you any experience symptoms such as leg pain, joint pain, chest pain, or general fatigue. When you have reached a set time limit (such as 5 minutes), or when you ask to stop because of fatigue or because your symptoms have become too painful, this portion of the test will end.

After you exercise, you will be asked to lie down and the technologist will perform a second ABI test, measuring pressures every minute until they return to the pre-exercise level.

What happens if I cannot exercise on a treadmill?

Some women are unable to perform the standard treadmill exercise test because of advanced age, excess weight, arthritis, or other health problems. If you are not able to exercise on a treadmill, or if a treadmill is not available where you are having the test, you may have an alternate version of the exercise test, called the “tip-toe” test.

A baseline ABI will be taken before you exercise, just as in the standard test. You will then be asked to stand flat-footed and use your calf muscles to raise your heels off the floor as far as you can. If you need to, you can rest your fingertips against a wall for support. You will rise up on your toes 50 times, or until you experience symptoms.

When you are finished exercising, your ABI will be measured again and compared to the results before you exercised. The tip-toe test is about 95% as accurate as a treadmill exercise test for diagnosing PAD.

If you cannot perform the tip-toe test, a 6-minute walk test may be used to evaluate your walking ability. You will be asked to walk up and down a hallway that is at least 100 feet long for 6 minutes. The test can be difficult and you may become tired and out of breath, but you can stop and rest during the test if you need to. When the time is up your doctor will measure the total distance you were able to walk. The 6-minute walk test helps your doctor determine how much PAD is limiting your movement, and it may be repeated later to monitor how well your PAD treatment is working.

What happens after the test?

You can eat, drink, and resume normal activities immediately following an exercise test. If you do not exercise regularly, you may experience muscle aches or fatigue afterwards. A preliminary report may be available right after the test, but the full report usually takes a day or two.

What do the results mean?

The results of an exercise test show whether or not PAD is limiting your walking ability, and how much. The test reports your pain-free walking distance or time, your maximal walking distance or time, and any changes in your ABI before and after exercise.

In healthy women, blood pressure readings in the arm and ankle rise together during exercise, and the ABI stays the same (or is slightly higher) after exercise compared with before. If your ABI does go down after you exercise, your leg pain is probably not caused by PAD.

In women with PAD, the ABI after exercise is lower than the ABI at rest. This is because leg arteries narrowed by PAD are unable to provide enough blood flow to the leg muscles during exercise less blood flow to the legs compared with the arms results in a lower ABI.

A study of 3,209 patients with PAD (29% were women) found that patients whose ABI dropped by just 6% after exercise had a 60% higher risk of dying in the next 8 years. The more the ABI drops, the higher your risk. An ABI that fell by more than half after exercise increased a person’s chance of dying by nearly 5-fold.

What are the risks of the test?

Although it is very rare, there is a small chance that the stress placed on your heart during the test could cause a heart attack or other heart problems, especially if you have coronary artery disease or heart rhythm problems. However, you will be closely monitored and the test will be stopped if there is any sign of a problem.

What happens next?

All women with symptoms caused by PAD in the legs should be referred to a structured PAD rehabilitation program that includes exercise, which can reduce PAD symptoms and improve walking ability. See Exercise & Lower Extremity PAD Rehabilitation (coming soon) for more.

In addition to rehabilitation, you may also need medication or procedures to help relieve your PAD symptoms and prevent future problems.

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