Patient education: ECG and stress test (The Basics)

What is an ECG? — An ECG, or "electrocardiogram," is a test that records a person's heart rate (how fast it beats) and rhythm. It does this by measuring the electrical activity in the heart.

A normal heartbeat happens when an electrical signal starts in a spot near the top of the heart. This signal follows a path to spread across the heart. As it spreads, the signal causes the heart muscle to squeeze. Each time the heart squeezes ("beats"), it pumps blood through the whole body.

What is a stress test? — A stress test measures how well the heart works when it is beating fast and working hard. When the heart pumps fast, it needs more blood. A stress test helps doctors see if the heart is getting enough blood during these times. A stress test is sometimes called an "exercise test" or a "treadmill test."

A person can have an ECG without having a stress test. But if a person has a stress test, they will always have an ECG with it.

Why might I need 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

●Check for side effects from other medicines

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 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.

●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 or have sex after a heart attack

How do I prepare for an ECG or a stress test? — To prepare for a stress test, you will probably need to avoid eating, drinking, or smoking for 3 hours beforehand. If you are taking 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 a stress test, wear comfortable clothes that you can exercise in. You should also bring any inhalers you use to help your breathing.

What happens during an ECG and stress test? — For an ECG, a doctor, nurse, or technician will 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, they will "stress" your heart and raise your heart rate by doing 1 of the following:

●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)

●Have you use an "arm ergometer" – This machine is similar to a bike, but you pedal with your hands instead of your feet. It is sometimes called a "hand crank" or "hand bike."

●Give you medicine to make your heart beat faster – People who can't walk or pedal a bike can get medicine instead of exercising. You might also squeeze a small ball, or lift up or move your legs to help make your heart beat faster.

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

During the stress test, the doctor or nurse will watch you. They 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 that the test is over.

What are the risks 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.

More on this topic

Patient education: Chest pain (The Basics)
Patient education: Coronary artery disease (The Basics)
Patient education: Heart failure (The Basics)
Patient education: Heart attack (The Basics)
Patient education: Atrial fibrillation (The Basics)
Patient education: Hypertrophic cardiomyopathy in adults (The Basics)
Patient education: Nuclear heart testing (The Basics)
Patient education: Echocardiogram (The Basics)
Patient education: Long QT syndrome (The Basics)

Patient education: Chest pain (Beyond the Basics)
Patient education: Heart failure (Beyond the Basics)
Patient education: Heart attack (Beyond the Basics)
Patient education: Atrial fibrillation (Beyond the Basics)
Patient education: Hypertrophic cardiomyopathy (Beyond the Basics)