What is a stress test?

An exercise stress test is often used to diagnose coronary heart disease. BHF Professor Ajay Shah tells our Senior Cardiac Nurse Emily McGrath more.

Cardiac stress test

An exercise stress test, also called a cardiac stress test, exercise ECG or stress test, is used to assess the range of ability of the heart. All of us do varying levels of activity in our day-to-day lives. When we are sitting down, the heart isn’t working very hard. When we go for a brisk walk or a swim or a run, our heart has to do more work. The idea of an exercise test is to objectively assess how well the heart functions during increased activity. It is a very good way to assess if the heart is healthy.

Do I need to do anything to prepare for a stress test?

You will need to wear comfortable and appropriate clothing with trainers. You may be advised to avoid drinks with caffeine in, or eating a heavy meal, for two to three hours before the test, so that the measurements are as accurate as possible.

What does a stress test involve?

The test usually involves walking on a treadmill or using an exercise bike. The speed and incline of the treadmill will go up gradually. During the test you are carefully monitored to see what your heart rate and your blood pressure is doing. We also record the electrical activity of the heart through an ECG. An exercise treadmill test typically goes on for a maximum of 12 minutes. The average duration someone will walk for is around nine minutes.

Sometimes, medicine given by a drip is used to increase the heart’s activity instead, for example in patients who cannot walk very well. This type of stress test may also be combined with imaging of the heart to physically see how well the heart is pumping. The imaging may be done with an ultrasound (called a stress echo) or MRI (called a stress MRI) or a nuclear scan (called a stress nuclear scan). The principle of all these tests is the same – to increase the workload of the heart and carefully monitor your blood pressure, heart rate and heart function.

Will a stress test hurt?

It shouldn’t hurt at all. Some patients’ symptoms may be caused by exercise, so these symptoms may be provoked during this test, but should stop quickly when the test ends.

Cardiac stress test - Electrodes on chestWhat are the risks of a stress test?

Your symptoms will be carefully monitored and the person doing the test will know that they need to stop if any symptoms occur. There is no significant risk from the test, as it will be performed under controlled and monitored conditions. The test would be stopped well before you get to a level of exercise that would cause the heart to struggle.

It’s much safer to do a controlled test like this than to run 10km knowing that there might be something wrong with the heart.

Are there any after effects?

In the vast majority of cases, no. For someone who has a heart condition the test would be stopped before it causes any problems. It might take you 10 or 15 minutes before you get back to normal, but this is just the usual rest period after any type of exercise.

What will a stress test tell my doctor?

The test is designed to see how well the heart performs under stress. For example, if someone has a narrowing in one of the coronary arteries, that abnormality may show in the electrical tracing that we record during the test.  

Is there anyone that a stress test wouldn’t be suitable for?

If we know that someone has a severe cardiac problem then we wouldn’t always consider a stress test, but it is suitable for most people.

Will I need further tests after a stress test?

It’s certainly possible that additional tests may be required. A stress test is often used as a screening test. If the result is normal, then typically you won’t need further tests. If it’s not, you may require further tests, depending on the type of problem identified. A coronary angiogram is one of the most common follow-up tests.

What are the latest developments in stress tests?

We are constantly looking to make stress tests more accurate so they can provide more information. This is to reduce the need for additional tests. The latest developments are looking at how we can incorporate different ways of imaging the heart, for example by advanced MRI, so that we can reduce the need for invasive tests, such as coronary angiograms.

Professor Ajay ShahProfessor Ajay Shah

  • BHF Professor of Cardiology at King’s College London
  • Director of BHF Centre of Research Excellence, King’s College London
  • Consultant cardiologist at King’s College Hospital
  • Leads world-class research programme into heart failure

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