Why might my doctor order an ECG or a stress test? — Your doctor might order an ECG to:

  • See if you are having or had a heart attack
  • Look for other heart conditions or follow a known heart condition
  • Help figure out why you have chest pain, trouble breathing, dizziness, a fast heart rate, or other symptoms
  • Check how healthy your heart is before you have surgery
  • Check how well your heart medicines or other heart treatments are working

Doctors usually order stress tests to check for problems that can happen when the heart works hard. Your doctor might order a stress test to:

  • See if you have coronary heart disease, heart failure, or another heart condition – Coronary heart disease is a condition that puts you at risk for a heart attack and other types of heart disease. Some people have symptoms of coronary heart disease only when they exercise. Heart failure is a condition in which the heart doesn’t pump well.
  • Check how well your heart works after heart surgery.
  • Help figure out why you have chest pain, trouble breathing, or other symptoms.
  • See if you can safely exercise after a heart attack.

How do I prepare for an ECG or a stress test? — Before an ECG, you don’t need do anything special. But you should tell your doctor what medicines you take, because they might affect the test results.

To prepare for a stress test, you will probably need to avoid eating, drinking, or smoking for 3 hours beforehand. If you are on any heart medicines, you might also need to change or stop some of them before the test. Your doctor or nurse should tell you if you need to change or stop any of your medicines.

For your stress test, you should wear comfortable clothes that you can exercise in. You should also bring any inhalers that you use to help your breathing.

What happens during an ECG and stress test? — For an ECG, a doctor, nurse, or technician will first stick patches (called “electrodes”) onto your chest, arms, and legs (figure 1). Wires connect the patches to the ECG machine. The machine will measure and record your heart’s electrical activity and print out the results. Having an ECG doesn’t hurt.

For a stress test, the doctor, nurse, or technician will first do an ECG and measure your blood pressure. Then he or she will “stress” your heart and increase your heart rate by doing 1 of the following things:

  • Have you run or walk on a treadmill (figure 2)
  • Have you pedal a stationary bike (a bike that doesn’t move, except for the pedals)
  • Give you medicine to make your heart beat faster – People who can’t run or walk can get medicine instead of exercising.

Sometimes, doctors do imaging tests during a stress test. These kinds of tests can create images of the blood flow to the heart.

During your stress test, the doctor or nurse will watch you. He or she will check your blood pressure, do several ECGs, and ask how you feel. You might also need to breathe into a tube at certain times during the test. The test will end when you can’t exercise anymore or when your doctor or nurse tells you the test is over.

What are the downsides of an ECG and stress test? — An ECG has very few downsides. Some people get a mild rash where the patches were placed.

A stress test can have some downsides. When people exercise and their heart pumps fast, they can have symptoms such as:

  • An abnormal heartbeat
  • Trouble breathing
  • Feeling dizzy or faint

The medicines used during a stress test can also cause side effects, including headaches, dizziness, or nausea.