Exercise Stress Test
• What Is Stress Testing?
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|What Is Stress Testing?
A stress test refers to a group of heart disease tests which doctors use to evaluate the heart's ability to cope with increased demand. There are different types of 'stress' and many different types of 'tests'. Most commonly doctors use some form of exercise to stress to the heart, such as walking on a treadmill, pedaling a stationary bike or performing arm exercises. The second common type of stress is 'chemical', which involves using intravenous medications to artificially dilate the blood vessels in the heart, mimicking the effects of exercise (chemical stress test). The types of tests used for stress testing include an electrocardiogram (ECG), an echocardiogram (echo) and even a PET scan combined with a nuclear heart scan. For the purpose of this article we will focus on the ECG exercise test.
Also known as exercise tolerance testing and exercise stress testing, this test is most commonly performed to evaluate coronary heart disease (CHD) or its subcategory coronary artery disease (CAD). It can also be used to determine the prognosis (outlook) for patients with heart disease. A patient who has had a heart attack but can walk for 15 minutes on a treadmill without symptoms is statistically likely to live longer than a patient who cannot. During the test, the patient wears ECG electrodes attached to their chest to monitor the heart's reactions. The exercise machine, usually a treadmill, will be preprogrammed with speeds and inclines set in accordance to strict standardized protocols. Once the exercise is completed and the heart is considered 'stressed', the patient will be told to lie down and they will be monitored for another 15 minutes. The ECG readings are stored and printed for a doctor to analyze. If the test is ordered in combination with an echocardiogram (a type of ultrasound test for the heart), the echo will be done immediate after the exercise is completed. The images from an echo are stored on file and sent to a doctor, along with the ECG readings, for analysis.
signs of coronary heart disease. It will also evaluate the likely presence of ischemic heart disease which is caused by CHD and arteriosclerosis (fatty deposit builds up in the arteries). It may be that the patient:
1. It can help with the diagnosis of chest pain. Pain can be caused by narrowing of the arteries which supply blood to the heart. If so, the test will help determine if a heart catheterization or coronary angiography is needed to directly view any blockages.
2. Has angina attacks which are steadily becoming more severe and occurring more regularly.
3. Has had a heart attack and the doctors want to assess the damage.
4. Has palpitations (irregular heartbeats) which occur during exercise.
5. Has had heart bypass surgery or coronary angioplasty and the test will monitor the patient’s progress.
6. Is starting an exercise program and has certain risk factors for heart disease.
7. Is suspected of having a failing heart, this test can help with the diagnosis of heart failure.
8. Is starting a cardiac rehab exercise program and doctors wish to determine the patient's target heart rate. Or the patient is starting a home cardiac exercise program.
The test will be carried out in a physician’s office or at hospital. First up to 12 sticky patches called electrodes are attached to the chest area. These electrodes are then connected to the exercise ECG machine which will monitor the heart's activity. The patient's resting ECG rate may be recorded first, both sitting and standing. Blood pressure will be measured before the exercise begins and at the end of each exercise stage. As the test progresses the patient's systolic blood pressure should rise the longer they exercise. A level of up to 225mm Hg is considered normal although athletes can have higher levels. The diastolic blood pressure should fall as the test progresses. The aim of the exercise is for patients to reach a specified target rate determined by their age.When the patient steps on the treadmill, the test begins. Their progress is set by what is called the Bruce protocol. This is the most widely used protocol which determines the parameters for exercise stress testing. The protocol has 7 stages, each lasting 3 minutes resulting in a total of 21 minutes of exercise. In stage 1, for example, the patient walks at 2.7km (1.7 mph) and the incline is 10 percent. The test may be modified slightly if the patient has had a heart attack (myocardial infarction) within the past 7 days. Usually however patients rarely need to exercise for the full 21 minutes. Normally they reach a satisfactory heart rate after 9 to 12 minutes. A common reason for stopping early is that patients experience breathlessness and fatigue due to low fitness levels. The recording of their ECG continues for another 15 minutes. However if the test is to be useful the patient needs to reach their goal heart specific to their age. If they are not physically able to achieve this, then a chemical stress test may be more appropriate.
A doctor will stop the test if he notes:
• Severe chest pain, dizziness or dyspnoea (shortness of breath).
• A drop in systolic blood pressure (by more than 20 mm Hg).
• A rise in blood pressure (systolic more than 300 mm Hg, diastolic more than 130 mm Hg).
• Ataxia (balance and movement become affected).
Interesting: Heart Disease Statistics and UK Heart Disease Statistics.
2. Blocker medications (beta blockers and calcium channel blockers) should normally be discontinued 24 hours before the test, and digoxin (used to treat congestive heart failure and which may cause false positive results) should be discontinued one week before testing. Ask your doctor for specific advice however before quitting any prescribed medication.
3. Avoid all caffeine products for 24 hours before the test. This includes coffee, tea, chocolate, all sodas (even caffeine-free ones) and certain pain relievers that contain caffeine.
4. Avoid eating, smoking or drinking for 3 hours before the test.
How Safe Is The Test?
Stress tests are generally safe as long as patients are carefully selected. Serious complications such as heart attack or death are rare and occur in about 0.01 percent of cases. The incidence of ventricular tachycardia or fibrillation is about 1 in every 5,000. All facilities that carry out the test will carry resuscitation facilities in case they are needed.
Exercise-only stress tests may be difficult to interpret in certain patients which is why other imaging tools such as echocardiography or nuclear imaging may be added. These additional imaging tests can be very expensive, which is why they are not always ordered. An exercise-only stress test can normally detect about 70 percent of CHD cases. This means however that it cannot rule out the disease (30 percent may be missed). For this reason, probability is taken into account. For example, in low risk group, that is women under the age of 40 (men under 30), a positive result may be seen as a false positive and negative results add little information. In high risk groups, that is women for example aged over 50 with signs of angina, a negative result cannot rule out CHD because of the 30 percent 'miss' factor. Stress testing is therefore considered of best diagnostic use in patients who have risk factors for heart disease.
You should expect to hear about the results of your test within 1 to 3 working days. If the results are normal, no further testing or treatment may be needed. If however the results show any abnormalities or you were physically unable to complete the test, further imaging tests may be ordered such as echocardiography, nuclear imaging, CT or PET scans.
An exercise stress test averages between $250 and $300. If it is combined with an echocardiogram the cost can increase to $1,400.
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