A stress test, also known as an exercise test or treadmill test, can give an idea of how well a person’s heart works during physical activity. It can also help diagnose various heart conditions.

A stress test typically involves walking on a treadmill or using a stationary cycle while medical devices monitor breathing, blood pressure, heart rate, and heart rhythm.

Some people, such as those with arthritis, may not be able to do the activities involved in an exercise stress test. Instead, a doctor will give these people a drug to make their heart work harder, as it might during exercise.

In this article, learn why a doctor may recommend a stress test and what to expect during one.

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Stress tests can help a doctor diagnose various heart conditions. They can also help identify a person’s risk before undergoing an activity that may put strain on their heart and show how well a person’s heart handles a workload.

A doctor may recommend a stress test if a person has symptoms that could indicate a heart condition, such as:

  • difficulty breathing
  • chest pain
  • dizziness
  • a fast or irregular heartbeat

A doctor may also recommend a stress test if a person:

  • is undergoing heart treatment
  • is due to have heart surgery
  • is considering starting a vigorous exercise program

According to a study that researchers presented at the American Thoracic Society conference in 2013, a stress test may also identify people with obstructive sleep apnea who are most at risk of experiencing life threatening complications.

When the heart pumps harder during exercise, the stress test can reveal issues such as low blood supply through the coronary arteries. These problems might not be apparent at other times.

A doctor may advise the person not to consume caffeinated drinks or take certain medications on the day of the test. These substances could affect the results.

They may also ask them not to smoke or to eat or drink anything except water for 2–4 hours before the test.

Anyone who usually has an inhaler should bring it to the test and make sure that the doctor knows about it.

For an exercise stress test, a person should wear comfortable clothes and walking shoes.

The test involves the person being hooked up to various medical devices that monitor the heart. To achieve this, the doctor will place:

  • sticky patches, or electrodes, on the chest
  • a blood pressure cuff around the arm
  • a pulse monitor on the finger

If the person will not be exercising, they will receive an infusion of a certain medication into their arm through an intravenous (IV) line.

Some factors the doctor will aim to measure include:

  • heart rate
  • breathing
  • blood pressure
  • how exercise affects fatigue levels
  • heartbeat and heart waves

There are a few different ways of completing a stress test, depending on the person’s needs.

Exercise stress test

During a stress test, the doctor will aim to determine the person’s heart rate, blood pressure, breathing, and how tired they feel during different levels of physical activity.

Here is a step-by-step description of what happens during a stress test using a treadmill:

  1. Having attached the devices to monitor the heart, the doctor will take some readings.
  2. Next, the person will stand on the treadmill.
  3. As the treadmill starts to move, the person will walk slowly.
  4. The treadmill speed will gradually increase.
  5. The treadmill may go into an uphill, or incline, position.
  6. Toward the end, the person may need to breathe into a mouthpiece to measure the air they breathe out.
  7. The treadmill will stop, and the person will lie down while the doctor takes their blood pressure and other readings.

The person will exercise for 10–15 minutes, but they can ask to stop at any time if they feel unwell.

If the person experiences any of the following, the doctor might stop the test:

They may also stop the test if the electrocardiogram device detects any unusual changes.

Qualified medical professionals are always on hand in case of adverse effects.

Stress test without exercise

If a person is unable to exercise, the doctor may use a certain medication to trigger the same process.

In this case, they will attach electrodes to the chest and deliver the medication into the person’s arm through an IV line. The medication will take 15–20 minutes to deliver.

The medication will stimulate the heart. It may cause effects similar to those that occur during exercise, such as flushing or shortness of breath.

Nuclear stress test

Depending on the results, the doctor may recommend a nuclear stress test as a next step.

Also known as a nuclear heart test or radionuclide scan, this can give a more detailed and more accurate assessment of the heart.

The process is similar to that of the exercise stress test, but the doctor will inject a tracer dye into the arm that will highlight the heart and blood flow on an image. The dye will also show any areas of the heart where blood is not flowing. This can suggest a blockage.

As with the exercise test, if a person cannot exercise, the doctor may use a medication instead.

The person will then undergo an imaging test that involves a small amount of radiation, such as a single photon emission computer tomography or cardiac PET test.

The doctor will take two sets of images, each covering 15–30 minutes. They will take the first just after the person has exercised and the second when their body is at rest, either later that day or the next day. They may also take “at rest” images before the person exercises.

In this way, the doctor can compare how the heart looks and functions normally and while under stress.

This test is not suitable for anyone who is or may be pregnant, as radiation may harm the fetus. Anyone who is breastfeeding should let the doctor know beforehand.

Both the stress test and the nuclear stress test are usually safe.

In rare cases, however, they could trigger adverse effects. These include a heart attack or changes in heart rhythm that do not disappear after the test.

Statistics suggest that this happens in around 1 in 10,000 cases. For this reason, doctors do not recommend this test unless a person meets certain criteria.

A person should not undergo an exercise stress test if they:

  • have certain heart or cardiovascular conditions
  • cannot exercise due to conditions such as arthritis
  • have recently had a stroke or heart attack

Possible results of the test include:

  • normal blood flow during exercise and rest
  • normal blood flow when resting but not during exercise, possibly indicating a blocked artery
  • low blood flow when exercising and resting, suggesting coronary artery disease
  • no dye in some parts of the heart, implying tissue damage

If the results of the stress test raise no concerns, the person will need no further tests.

If the results are unclear or suggest that damage is present, the doctor may recommend further tests or treatment.

A stress test can show how well the heart is working and help diagnose various heart conditions.

It can also give an idea of how much strain a person’s heart can cope with. This can be helpful when planning for heart surgery or a vigorous exercise program.

The test usually involves walking on a treadmill while a doctor monitors heart activity. However, people with reduced mobility may need to receive a certain medication to produce a similar effect.

A stress test can give an idea of a person’s heart health and guide recommendations on exercise and other forms of therapy.

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