Introduction to Noninvasive Cardiac Imaging
Noninvasive cardiac imaging refers to a combination of methods that can be used to obtain images related to the structure and function of the heart. As opposed to invasive techniques, which require catheters to be inserted into the heart, noninvasive tests are easier to perform, are safe, and can be used to detect various heart conditions, ranging from plaque in the arteries that supply the heart muscle (known as coronary artery disease) to abnormalities that impair the ability of the heart to pump blood.
As a result of technological advances, the number of available noninvasive cardiac tests that physicians can order has increased substantially over the last decade (the Figure). Although these tests have improved physicians' abilities to diagnose and treat heart disease, it is important to understand that not all individuals benefit from noninvasive cardiac imaging. Therefore, these tests should be ordered only at the advice of a physician and should be considered only if the information provided would influence subsequent treatment with medications, procedures, or lifestyle interventions.
When Is Noninvasive Cardiac Imaging Used?
The goal of cardiac testing may include any of the following: (1) to identify or exclude various forms of heart disease as a reason for a person's symptoms, (2) to establish the risk of developing future heart disease such as a heart attack, and (3) to decide on the need for additional medical therapies and procedures. For instance, in patients with coronary artery disease, the results of imaging tests could be used for selecting between procedures such as placing stents in the arteries of the heart or performing bypass surgery versus pursuing aggressive treatment with medications.
Do I Need a Cardiac Imaging Test?
Although some cardiac imaging tests can be used to evaluate the risk of individuals who do not have any symptoms, the majority of tests are performed to evaluate the cause of symptoms that may be attributable to cardiovascular disease (Table 1). It is important to know that although some individuals with narrowing in the coronary arteries may experience chest discomfort or shortness of breath—most often during physical activity—such symptoms can be caused by other reasons that are not related to heart disease. Table 2 lists questions about cardiac imaging tests that you should discuss with your physician.
What Are the Different Types of Cardiac Imaging Tests Available?
Table 3 provides an overview of the available noninvasive cardiac tests that your physician may order. Although different types of tests may be used to evaluate different disorders, several different testing options may be suitable for evaluating the same condition. Therefore, if testing is needed, it is important for your doctor to choose the test that she or he feels is the most appropriate for your clinical condition.
How Will My Physician Choose Among These Tests?
The choice of test type will depend on the type of heart disease being evaluated and your medical history. For instance, individuals who already have known coronary artery disease may require a test that identifies abnormalities in blood flow under rest and stress conditions. On the other hand, in lower-risk patients, exercise treadmill testing or cardiac computed tomography can be considered (see Table 3 for details). Because not all tests are available in all centers and different facilities may have different areas of expertise, your doctor should choose a test that your local hospital or clinic has sufficient experience in performing and interpreting.
Most computed tomography examinations and some magnetic resonance imaging examinations require the use of intravenous contrast administration. Use of such contrast should be avoided in patients with abnormal kidney function (If needed, kidney function can be determined with a blood test). Furthermore, patients who are overweight may have lower image quality for some types of tests (stress echocardiogram, nuclear single-photon emission computed tomography) and may benefit from alternative techniques (eg, cardiac magnetic resonance imaging, nuclear positron emission tomography) if available.
What Are the Risks of Testing?
The majority of cardiac imaging tests are extremely safe. During tests that use exercise or medications that simulate the effects of exercise, the chance of having a heart attack or dying as a result of the test is less than 1 in 10 000.
Tests that use a radioactive medication (nuclear cardiology) or x-rays (computed tomography) are associated with a small exposure to radiation. Table 4 provides a comparison of the radiation dose of commonly used cardiac imaging tests relative to nonmedical exposure from background radiation. Although there is no direct evidence linking the small amounts of radiation used in imaging tests to the development of cancer, given the known harmful effects of larger amounts of radiation, it is prudent to limit unnecessary exposure to radiation, particularly in younger individuals because they may be more susceptible to the potential harmful effects of radiation.
It is important to understand that for the majority of patients who require cardiovascular testing, the benefit of these tests far outweighs the small amount of risk. If you have questions about the benefits and risks of the examination, it is always best to talk with your doctor. Before your test, technicians and/or physicians specializing in imaging may also be able to provide you with more information about your specific test.
The author acknowledges Erin West, chief exercise physiologist, Brigham and Women's Hospital.
The information contained in this Circulation Cardiology Patient Page is not a substitute for medical advice, and the American Heart Association recommends consultation with your doctor or healthcare professional.
- © 2012 American Heart Association, Inc.