The Cardiac Stress Test
In the US, coronary arteries continue to be a major source of illness and death. Although there have been significant advances in disease prevention, treatment of heart disease and the costs to society in the form of lost wages and work hours place a huge burden on our healthcare system.
Cardiovascular disease is still the leading cause of deaths throughout the world. In particular, the rate of CVD has increased among low- and middle-income populations. Lifestyle factors such as diet and physical activity can help stave off the health problems associated with it.
For those with a history or high risk factors for heart disease, use of the cardiac stress test is an effective means of evaluating for potential heart dysfunction. The cardiac stress test provides us with a valuable means of assessing therapy and rehabilitation following a heart attack.
What is the Cardiac Stress Test?
The cardiac stress test records the electrical activity of the heart along with blood pressure while under the physical stress of exercise. This is synonymous with an exercise tolerance test. The essential goal of the test is to induce the stress response through physical activity or drug stimulation.
The test is non-invasive, as it requires no surgery or needles. For individuals with a risk of coronary heart disease, this test provides important diagnostic and prognostic information for evaluating treatment.
The most commonly used stress test is the exercise electrocardiography (ECG). Although there are numerous types available, the one used for an individual will depend on a number of factors including their ability to perform the required physical activity in an ECG.
In addition to the ECG, exercise combined with stress imaging such as the exercise echocardiography and stress radionuclide myocardial perfusion imaging (MPI) are also commonly used for cardiovascular testing.
Which stress test to use depends on the following factors:
- Clinical indications
- Individual’s ability to perform exercise
- Resting ECG
- History of revascularization
- Patient’s physical characteristics
Cardiac Stress Test Data
There are a number of benefits to the data collected from the cardiac stress test. It can be used to investigate symptoms such as chest pain and shortness of breath. The test can determine if blockages are present in the arteries that supply the heart.
Many patients present irregular heart rhythms, specifically during exercise. The cardiac stress test is a means of assessing any potential risk, and can determine an individual’s safety level with regards to starting a new exercise program.
For patients who’ve suffered a myocardial infarction, a stress test can help strategize an appropriate intensity level for rehabilitative work.
For those who are asymptomatic, yet nonetheless at a high level of risk, the test serves as a preventative screening measure.
Who Needs a Cardiac Stress Test?
The cardiac stress test isn’t for everyone. Dr. Golshani will evaluate your patient’s medical history, symptoms, use of medication, and activity level to determine whether or not to use a stress test.
Those with symptoms that indicate the presence of coronary heart disease are candidates for the test, as it will help assess their diagnosis and overall risk.
The presence of chest pain, cardiomyopathy, select arrhythmias and valvular heart disease can indicate the need for a stress test. It can be useful prior to non-cardiac surgery as well. For those experiencing chest pain, stress testing should only be done after the symptoms have been relieved.
For asymptomatic patients, the use of a stress test is generally not considered appropriate. However, those who are involved in high-risk professions or otherwise have a high risk of CHD (coronary heart disease) can be considered appropriate candidates in some cases.
Different Types of Cardiac Stress Tests
Exercise is the commonly preferred stress modality used in testing. It’s applied in cases where the patient can reach required exercise intensity levels, and it provides practitioners with valuable data related to symptoms and cardiovascular function.
To determine qualification for an exercise stress test, a patient should generally be able to walk for more than five minutes. But in general, a specified level of exercise required to attempt a stress test has not yet been defined.
The variables that are measured for data include the following:
- Exercise duration
- Exercise-induced blood pressure changes
- Heart rate recovery
- Ventricular function
Practitioners use the Duke Treadmill Score to evaluate the level of risk
(low, intermediate, high) as they relate to the ECG measurements and symptoms.
In addition to exercise, a pharmacologic stress can be applied in testing. For those who aren’t able to perform sufficient levels of exercise, this type of test is used. Pharmacologic testing can be performed with a vasodilator as well as drugs that have inotropic or chronotropic effects.
Vasodilators act to increase the flow of coronary blood. For pharmacologic stress tests, vasodilators are generally preferred. These can also be combined with exercise.
The nuclear stress test is another option for cardiac stress testing. It is effective in determining the parts of the heart that are functioning abnormally. In this test, a radioactive substance is injected into the patient. Using a camera, the doctor can identify the substance within the body to produce an image of the heart tissue. Areas where there is decreased blood supply will be indicated as a result.
How Do I Choose The Right Test?
The appropriate test to use will depend on a variety of factors. The optimal test is based on such factors as resting ECG and the patient’s capacity for exercise. If an individual cannot exercise to an appropriate intensity level, then a pharmacologic test will be used.
In all other cases, the exercise ECG will be the preferred method. It is the initial test for the majority of people who don’t have conditions that include left bundle branch block or pre-excitation of the ventricles.
What Is The Procedure Like?
The equipment required for the exercise stress test include:
- Bicycle ergometer or treadmill
- Monitoring system
- Defibrillator
- Medical crash cart
The evaluating practitioner is present along with an assistant trained in cardiac life support.
Prior to undergoing a stress test, the patient receives instructions to prepare in advance. This includes a restricted food intake for a period of 6 to 12 hours prior to administering the test.
Comfortable clothing and shoes are recommended. A review of prescription medications is completed, and in some cases, dosages are modified in preparation for the test.
Assessing resting ECG is performed prior to the test. The ECG determines a baseline level of heart activity. An echocardiogram examines the movement and physical characteristics of the heart. Diabetic patients should have their glucose monitors with them during testing.
To apply the test, the practitioner attaches electrocardiogram electrodes to the patient. Blood pressure and resting ECG are measured. Using the treadmill or bicycle, the patient begins to exercise. The exercise intensity is increased at intervals of between 2 to 3 minutes.
ECG and blood pressure are continually monitored. Any symptoms are also noted as the patient exercises until the target heart rate is achieved or to exhaustion. Any chest pains, changes in ECG, or heart-related symptoms are grounds to stop the test.
Once the test is complete, the patient is monitored until all levels reach baseline once again. Although the test itself is brief, the entire procedure commonly requires a full hour.
What Can The Stress Test Tell Me?
A cardiac stress test is an invaluable tool for gathering data. A positive result indicates the potential for heart-related risks and CHD.
A low supply of oxygen to the heart will often be indicated in ECG changes. Any severe shortness of breath or chest pains are also key indicators of heart issues that should be further investigated.
If the patient’s heart rate or blood pressure fails to adequately increase during the exercise, this can indicate CHD. Although not completely accurate, the cardiac stress test is still an important tool in diagnosing symptoms related to heart health.
The stress test allows for the detection of severely blocked arteries. Arteries that are at least 70% narrowed will likely lead to a positive test result. When these blockages rupture and form clots, the risk for heart attacks increases significantly.
The exercise stress test is the preferred initial method for individuals who can sustain the physical activity required. It measures the ability of the heart to respond to physical exertion, and doctors can use the stress test to ensure that there is adequate flow of blood to the heart. They can evaluate medication efficacy and determine the likelihood of CHD through proper stress testing.
There are a number of types of stresses in addition the exercise electrocardiogram. Pharmacologic and nuclear modalities can be beneficial in certain cases. Choosing the right test to administer will yield the best results and provide the most benefit to your health.
The Art of Healing
Dr. Roya Golshani, a board certified primary care physician, has been practicing general internal medicine since 2002. She is a passionate internist who not only practices internal medicine, but specializes in Women’s Health as well. With her additional training in medical, developmental, and psychological issues, she is fully capable of working with you to solve your problems. Talk with her today to
learn more about the cardiac stress test and how you can benefit from it.
