Exercise Cardiac Stress Test Procedure

Coronary artery disease (CAD) affects over 600 000 Australians and is implicated in approximately one in 5 deaths. Coronary angiography is the gold standard for identifying CAD, although it is invasive and not without risk of complication.

Cardiac stress testing is useful in the risk stratification of chest pain; noting that 15–39% of angiograms performed are normal.

Coronary artery disease (CAD) affects over 600 000 Australians and is implicated in approximately one in 5 deaths. Coronary angiography is the gold standard for identifying CAD, although it is invasive and not without risk of complication.

Cardiac stress testing is useful in the risk stratification of chest pain; noting that 15–39% of angiograms performed are normal.

Cardiac stress testing includes stress electrocardiography (ECG) – also known as exercise stress test (EST) – and stress echocardiography.

A detailed discussion of other tests for the noninvasive assessment of CAD, such as nuclear stress testing or computerised tomography (CT) coronary angiography, is beyond the scope of this article.

The exercise stress test involves exercising on a treadmill while you are closely monitored.

When should cardiac stress testing be ordered?

The main reason for cardiac stress testing is the risk stratification of known or possible CAD. The annual risk of cardiovascular mortality can be quantified from stress test results by measures such as the Duke treadmill score (low risk equating to <1% per year cardiovascular mortality, high risk >5% per year cardiovascular mortality).

Other indications include work-up for potential cardiac causes of dyspnoea (noting dyspnoea can be a cardiac equivalent symptom of CAD), and evaluation of the effects of exercise on valvular dysfunction, pulmonary pressures or arrhythmia (eg. chronotropic incompetence), as well as risk assessment in the postinfarct, preoperative or high risk patient populations.

There are advantages and limitations to each of the different testing modalities for the evaluation of myocardial ischaemia.

Why is this test performed?

The test is used to:

  • Determine your likelihood of having coronary artery disease
  • Identify abnormal heart rhythms
  • Evaluate the effectiveness of your cardiac treatment plan
  • Help you develop a safe exercise program

Can I eat or drink on the day of the test?

Yes. However, DO NOT eat or drink anything except water for four hours before the test.
Avoid all products that contain caffeine for 24 hours before the test.

In general, caffeine is found in coffee, tea, colas and other soft drinks, most chocolate products, as well as strawberries (these contain a small amount of caffeine), as caffeine will interfere with the results of the test.

Also avoid decaffeinated or caffeine-free products for 24 hours before the test, as these product contain trace amounts of caffeine.

DO NOT SMOKE ON THE DAY OF THE TEST, as nicotine will interfere with the results of your test.

Are there any contra-indications to testing?

Absolute contraindications to cardiac stress testing include acute myocardial infarction (including the presence of new left bundle branch block [LBBB]), high risk unstable angina, symptomatic severe aortic stenosis, uncontrolled arrhythmia causing symptoms or haemodynamic instability, unstable heart failure, acute pulmonary embolus and acute aortic dissection.

What are the precautions?

Relative contraindications include left main coronary stenosis, severe arterial hypertension, electrolyte abnormalities, hypertrophic obstructive cardiomyopathy and uncontrolled arrhythmia.

In the presence of a relative contraindication the test may still proceed if the benefit of identifying ischaemia outweighs the risk of performing the test.

It is important to ensure that the appropriate stress modality is ordered: if patients cannot walk at a reasonable workload, order an imaging pharmacological stress test (eg. dobutamine stress echocardiogram or persantin nuclear stress test), noting that a stress ECG cannot be done on its own using pharmacological stress.

Should I take my medications the day of the test?

Since many over-the-counter medications contain caffeine (such as diet pills, No Doz®, Excedrin® and Anacin®), DO NOT take any over-the-counter medication that contains caffeine for 24 hours before the test.

Ask your physician, pharmacist or nurse if you have questions about other medications that may contain caffeine.

DO NOT take the following heart medications on the day of your test unless your physician tells you otherwise or if it is needed to treat chest discomfort the day of the test:

  • Isosorbide dinitrate (for example: Dilatrate®, Isordil®)
  • Isosorbide mononitrate (for example: Imdur®, Ismo®, Monoket®)
  • Nitroglycerin (for example: Minitran®, Nitropatches®, Nitrostat®)

Your physician may also ask you to stop taking other heart medications on the day of your test. If you have any questions about your medications, ask your physician.

If you use an inhaler for your breathing, please bring it to the test.

NOTE: Do not discontinue any medication without first talking with your physician.

Guidelines for people with diabetes

If you take insulin to control your blood sugar, ask your physician what amount of your medication you should take the day of the test. Often, your physician will tell you to take only half of your usual morning dose and to eat a light meal four hours before the test.

If you take pills to control your blood sugar, do not take your medication until after the test is complete.

Do not take your diabetes medication and skip a meal before the test.

If you own a glucose monitor, bring it with you to check your blood sugar levels before and after your test. If you think your blood sugar is low, tell the lab personnel immediately. Plan to eat and take your diabetes medication following your test.

What should I wear on the day of the test?

Please wear or bring comfortable clothes and shoes suitable for walking. Please do not bring valuables. You will be given a locker to store your belongings during the test.

What happens during the test?

Your test will take place in the Stress Lab. The testing area is supervised by a physician.

First, a stress lab technician will gently rub 10 small areas on your chest and place electrodes (small, flat, sticky patches) on these areas.

The electrodes are attached to an electrocardiograph (EKG) monitor that charts your heart’s electrical activity during the test.

Before you start exercising, the technician will perform a resting EKG, measure your resting heart rate and take your blood pressure.

You will exercise on a treadmill. The lab personnel will ask you to start exercising and will gradually increase the intensity of exercise. You will be asked to continue exercising until you are exhausted.

At regular intervals, the lab personnel will ask how you are feeling. Please tell them if you feel chest, arm or jaw pain or discomfort; short of breath, dizzy, lightheaded or if you have any other unusual symptoms.

The lab personnel will watch for any changes on the EKG monitor that suggest the test should be stopped.

After the test, you will walk slowly for a few minutes to cool down. Your heart rate, blood pressure and EKG will continue to be monitored until the levels are returning to normal.

How will I feel during the test?

You will be encouraged to exercise until you are exhausted. It is normal for your heart rate, blood pressure, breathing rate and perspiration to increase.

How long does the test take?

The appointment will take about 60 minutes. The actual exercise time is usually between seven and 12 minutes.

How do I get the results of my test?

After a cardiologist has reviewed your test, the results will be entered into your electronic medical record. Your physician will have access to the results and will discuss them with you.

What are the risks?

Although the test is generally safe, there is a small risk of acute myocardial infarction (~1:5000 tests) and death (~1:10 000 tests). Patients need to consent to this risk.

Are there any special requirements?

Withholding rate-controlling medications such as beta-blockers is standard practice before stress testing (withhold the night before and morning of the test for twice daily beta-blocker, and the morning of the test for once daily beta-blocker); 85% of maximal predicted heart rate (MPHR = 220 bpm – age) must be achieved for the test to be diagnostically accurate.

The decision to withhold medicines must be tailored to the individual patient’s risk of rebound hypertension, ischaemia or tachyarrhythmia.

What do I tell my patient?

Before the stress test you will be connected to a 12-lead ECG and a baseline ECG recording will be performed (Figure 1). If you are undergoing a stress echocardiogram, a baseline echocardiogram (ultrasound) will also be performed to assess the structure and function of your heart.

A staff member will discuss your medical history before the test and measure your resting blood pressure. It is useful to bring your medications (or a list of your medications) on the day of the test.

What do the results mean?

The report should include an indication for the test and may comment on medications (particularly heart rate lowering medications) taken on the day of the test.

The results should describe the exercise protocol used, the exercise capacity in terms of time and workload achieved (protocol level, workload in watts or metabolic equivalent [METs] achieved), the haemodynamic response to stress (baseline and maximum blood pressure).

At what heart rate and at what percentage of maximum heart rate the test was ceased, for what reason the test was ceased, presence of left ventricular hypertrophy or inducible ischaemia (in terms of ST segment shift or wall motion abnormalities on echocardiography), presence or absence of arrhythmia and heart rate response during recovery.

The report may also comment on chronotropic incompetence and oxygen saturation during the test.

Source & More Info: RACGP and Cleveland Clinic



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