Exercise stress test

What is an exercise stress test?

An exercise stress test – also known as a cardiac stress test – assesses the heart’s range of ability, demonstrating how the heart is working during physical activity. Assessing how well your heart is functioning during exercise offers a good indication of the heart’s health.

You might need an exercise stress test to check if your blood flow to the heart has decreased due to a narrowing of the coronary arteries (coronary artery disease). The procedure might also be used to diagnose or monitor a range of other heart conditions.

What does a stress test show?

An exercise stress test can help your doctor understand how different heart conditions affect the performance of your heart with varying levels of activity. These conditions include but are not limited to the below:

• congenital heart disease
• cardiomyopathy
• valvular heart disease
• heart failure
• pulmonary hypertension

It can also be used to guide the treatment of heart disorders and check your heart before you are referred for surgical procedures such as a valve replacement or heart transplant.

Types of stress tests we offer

The type of stress test performed before and after exercise will depend on what investigation is being conducted. We offer a range of exercise stress tests, including:

• exercise stress echocardiogram (stress echo test)
• exercise tolerance test (exercise electrocardiogram test)
• cardiopulmonary exercise test (CPET)
• PET rubidium stress test (nuclear stress test)

All stress tests involve a patient being asked to exercise on a treadmill or exercise bike.

Exercise stress echocardiogram

An exercise stress echocardiogram shows how the heart functions during physical activity. The principles of this test work in the same way as a standard echocardiogram; using an ultrasound transducer to send out sound waves which bounce off the heart and create moving pictures of its chambers, walls, valves and surrounding blood vessels.

The images are taken before and after exercise, to show how well the heart performs under stress. In the majority of patients, stress echocardiograms are performed with the use of a contrast agent, which helps to give clear pictures of the heart for your consultant to see on the screen.

You will be asked to walk on a treadmill or pedal an exercise bike. During the test, we will monitor symptoms, cardiac rhythm, and blood pressure while walking on the treadmill and populate findings with echocardiographic images. In cases where patients are unable to walk on the treadmill, a pharmacological stress echocardiogram (also called a dobutamine stress echocardiogram) will be recommended.

• Pharmacological stress echocardiogram: This test uses a medication called dobutamine, which is injected into a vein to make your heart work in the same way it does during exercise, beating harder and faster. Your doctor will take pictures of your heart at the beginning and during the test. The heart rate, blood pressure and rhythm activity will be closely monitored throughout.

Exercise tolerance test

An exercise tolerance test, also called an exercise electrocardiogram (ECG), is the most common type of exercise stress test. It combines a standard exercise test with an ECG and blood pressure measurement

This test measures the heart’s electrical activity/blood pressure response while you are undergoing physical exercise. Patients are asked to exercise to their physical limit and may be stopped if they develop symptoms such as dizziness or chest pain.

Cardiopulmonary exercise test (CPET)

A cardio-pulmonary exercise test (CPET) is a specialist exercise test performed with both a respiratory and a cardiac physiologist and is most commonly used to determine causes of unexplained breathlessness, fitness for surgery or disease progression/treatment effectiveness.

You will be required to exercise either on a cycle ergometer (exercise bike) or a treadmill and be asked to continue until you are too tired to carry on.  The test looks for factors such as dysfunctional breathing patterns, peak oxygen uptake (called VO2 Max), possible post-exercise bronchoconstriction (exercise-induced asthma) assessed by pre and post-exercise spirometry and presence/absence of oxygen desaturation.

In addition, an end capillary blood gas will need to be taken before and immediately after exercise (this is only in adults, and not applicable for paediatric patients). This involves making a small incision at the base of the ear lobe and a small sample of blood is collected and analysed measuring, amongst other parameters, the pressures of oxygen and carbon dioxide in the blood. This is particularly useful at peak exercise and does not scar.

PET rubidium stress test (nuclear stress test)

A PET rubidium stress test, or nuclear stress test, measures the flow of blood to the heart before and after exercise. This test requires a small quantity of radioactive material called a radiotracer, which is administered through an IV. During the test, images are taken of the tracers moving through the arteries. This helps to identify any damage to the heart or areas with poor blood flow.

Exercise stress test preparation

Your doctor will give you instructions on how to prepare for your exercise stress test. You may be asked to stop eating, drinking or smoking for a certain amount of time before the procedure, and you could be required to avoid caffeine for 24 hours.

If you are taking any prescription or over-the-counter medications, inform your doctor. You might be asked to stop taking medication if it could interfere with the test. If you use an inhaler, take it along with you to the test and inform your doctor that you are using it. Wear comfortable clothes for your appointment. Continue taking your usual medication unless specified by your consultant.

People with specific heart conditions may not be suitable for an exercise stress test. These conditions may include but are not limited to:

• persistent or ongoing chest pain
• <6 weeks post-myocardial infarction (a heart attack) or percutaneous coronary intervention (e.g. angiogram)
• endocarditis (inflammation of the valves’ lining)
• myocarditis (inflammation of the heart muscle)
• pericarditis (inflammation of the pericardium, the protective fluid-filled sac around the heart)
• known blood clot
• aortic dissection (a tear in the main artery)
• resting systolic blood pressure >220mmHg
• resting diastolic blood pressure >120mmhg
• aortic stenosis (a type of heart valve disease)
• abnormal heart rhythms

How is a stress test performed?

Before your stress test, you will be asked questions relating to your medical history and level of fitness – this is to help decide on the right amount of exercise during your test.

This part of the test will depend on which type of exercise test you require. For example, if you are undergoing an exercise ECG the test will begin with electrodes (sticky patches) being placed on your chest and limbs. These sensors are connected via wires to a computer, allowing the electrical activity of your heart to be recorded. A blood pressure cuff will also be applied to your arm and will take measurements at specific periods during your test PET rubidium stress test.

During a standard exercise stress test, you will typically exercise on a stationary bike or treadmill, gradually increasing speed or incline (dependent on the protocol). Your doctor may ask you to breathe into a tube to assess how well you are breathing during physical activity.

Exercise will continue until you reach or exceed a target heart rate or show symptoms such as:

• chest pain
• low or high blood pressure
• severe shortness of breath
• dizziness
• arrhythmias

You’ll then stand still with the monitors in place as your breathing returns to normal. If you aren’t able to exercise, the test may be done using a drug that increases blood flow to the heart, simulating exercise.

Safe limits for the test will be discussed beforehand, and you will be able to stop the test at any time if you feel uncomfortable. The test usually takes about an hour and you can return home afterwards, resuming your normal activities.

Stress test results

The results of your stress test may be ready immediately, or in other cases, you may wait a few days before discussing them with your doctor at a follow-up appointment. Results will show how well your heart is functioning, and if the findings are normal, you may not require any more tests.

If a heart condition is identified and treatment intervention or further tests are required, your doctor will talk you through the next steps.