Assess heart health with a stress test
A stress test can be used to assess one's heart condition and rule out underlying cardiac disease.
The test's primary purposes are to:
• Determine the likelihood of having coronary heart disease and the need for further evaluation
• Evaluate the effectiveness of cardiac medications used to control angina and ischemia
• Check the effectiveness of procedures done to improve coronary blood flow in people with coronary blockages, for example, after stents placement or open heart surgery
• Identify abnormal heart rhythms that are revealed or worsened by exercise
• Assess the function of heart valves if they are too tight or too leaky
• Help to develop a safe exercise programme.
Here are the most common stress-testing methods:
• Treadmill stress test
This is usually the first stress test performed on patients who can walk and who have a normal baseline electrocardiogram (ECG). The person walks on a treadmill to determine exercise capacity — how far he or she can walk, and if there is any development of chest pain, ECG changes, or abnormal blood pressure fluctuations.
This test is able to diagnose coronary disease in 70 per cent of people only as it has a high rate of false-positive and false-negative results, especially if used in middle-age patients and in women.
In these populations, one of the imaging-coupled tests described below is preferred; the latter has a capacity of revealing coronary ischemia in 85 to 90 per cent of patients, leaving a small portion of people with unmasked disease or unclear diagnosis.
• Stress echocardiogram
An echocardiogram (“echo”) is a real-time graphic of the heart's movement. A stress echocardiogram can accurately visualise the motion of the heart's walls and its pumping function when the heart is stressed.
If, with effort, a given wall starts lagging behind the others, it could mean a coronary blockage in the vessel feeding this muscle segment, causing it to comparatively fail.
• Dobutamine stress test
This test is used in people who are unable to exercise. A drug, dobutamine, is given to make the heart race as if the person were exercising.
This way the physician can still determine how the heart responds to stress, but no exercise is required. It can be combined with echo or nuclear images.
• Nuclear stress test
In this case, a small amount of radioactive substance is injected into the patient's body, and then a special camera is used to identify the rays emitted from the substance once it reaches the coronary vessels.
These pictures are acquired both at rest and after stress, whether it is exercise or chemically-induced stress. Using this technique, areas of the heart that have a decreased blood supply can also be detected.
How to prepare for the stress test:
• Do not eat or drink anything except water, for four hours before the test
• Do not drink or eat foods containing caffeine for 12 hours before the test, as caffeine could interfere with the results of a chemical nuclear test
• Do not take these heart medications on the day of your test unless your doctor tells you otherwise, or if the test is specifically needed to assess your cardiac condition while on these drugs: beta-blocker, nitrates and calcium channel blockers
• If you use an inhaler for your breathing, bring it to the test
• If you have diabetes, you may be asked to hold your sugar tablets and insulin, or modify their dose or timing, on the day of the test
• Wear soft-soled shoes suitable for walking and comfortable clothes.
What happens during the stress test?
You will be hooked to an electrogram machine, and your baseline ECG and blood pressure measurement will be obtained.
You will begin to exercise by walking on a treadmill. The rate of exercise or degree of difficulty will gradually increase. You will be asked to exercise until you feel tired or you start having chest pain, dizziness or excessive shortness of breath.
It is expected that with exercise your heart rate and blood pressure will go high.
The heart speed would need to reach a target level before the test is considered conclusive, and the blood pressure should rise but within safe limits.
If an echocardiogram-based test is done, ultrasound pictures of your heart would additionally be acquired at the beginning and throughout the test.
If a nuclear imaging modality is being applied, two sets of pictures under the camera, at different times, are also collected.
A recovery phase of five to ten minutes usually follows a stress test.
• Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women's Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients' care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article