When are diagnostic tests used?
The tests covered in our Tests and Diagnosis section are used in three distinct situations. Some are used to diagnose urgent conditions such as a heart attack or unstable chest pain (e.g., blood tests to diagnose a heart attack, the resting ECG); others are mainly used to screen women with an intermediate to high risk for heart disease or those experiencing symptoms such as chest pain or shortness of breath (e.g., treadmill testing, echocardiography).
More recently, diagnostic tests are being used to detect very early signs of heart disease. The fatty plaque associated with atherosclerosis begins to buildup on the lining of the arteries in your early 20s, but you will not feel any symptoms or show signs of a problem during typical diagnostic testing until decades later when the blockage is big enough to significantly reduce blood flow. The idea behind these newer tests is to detect very early signs of trouble, such as a loss of elasticity in the lining of the artery, so that steps can be taken to prevent heart problems in the future. Blood tests for emerging risk factors such as C-reactive protein and calcium scans fall into this category.
Do I need to have a diagnostic test?
Whether you need to undergo diagnostic testing for heart disease is based on your risk of having heart disease. Your risk of heart disease depends on your age, sex, risk factors and what symptoms you have (if any). Overall, the lifetime risk of heart disease is slightly lower for women than men: 1 in 2 men, and 1 in 3 women 40 years of age will develop heart disease in their lifetime. If you have not already been diagnosed with heart disease, your doctor may use a risk calculator to determine whether you have a low, intermediate, or high risk of developing heart disease in the next 10 years.
If your risk score is low and you are not experiencing symptoms, you will not be sent for further testing. However, you should continue to keep your risk factors in check. If you have an intermediate or high-risk score or you have symptoms of heart disease, you may be sent for diagnostic testing.
What are noninvasive and invasive diagnostic tests?
There are various diagnostic tests available to detect heart disease, ranging from noninvasive tests that do not involve cutting through the skin (although some entail injections) to invasive tests where the skin is punctured. In cardiac catheterization, the most common invasive test, a thin flexible tube called a catheter is inserted into your groin or forearm and a thin wire known as a guide wire is used to guide the catheter into the different arteries of your heart. The purpose of this test is to find out if there are any blockages in the arteries of your heart. Noninvasive tests are used first in order to avoid unnecessary invasive testing. This is particularly important in women since up to 40% of women sent for cardiac catheterization do not have significant blockages in the arteries of their heart.
What are stress tests?
Some heart problems only show up when the heart is working hard (or stressed). During a noninvasive stress test, you will be asked to exercise to see if there are any areas of your heart that do not get enough blood and oxygen when under stress. People who are unable to exercise can have a stress test using chemicals that mimic the effect of exercise on the heart. Because your fitness level provides information about your risk for having a heart attack or dying from heart disease, an exercise stress test is preferred to a chemical stress test whenever possible.
Which noninvasive tests are used? The first noninvasive test generally given to women capable of exercise is the exercise ECG. This is because it is widely available and easy to perform. A negative (normal) test result means you do not have a heart problem and you do not need to undergo further testing. A positive (abnormal) test means you might have a heart problem. In women, this test often gives a false positive result—the test detects a heart problem but in reality there is none. If you have a positive (abnormal) test, you will be sent for further noninvasive testing to see if there really is a problem. The other types of noninvasive tests are imaging tests—these produce a picture, or image, of the heart.
What types of noninvasive imaging tests are there?
The noninvasive imaging tests listed below provide similar information and have a similar diagnostic accuracy in women. These tests require more skill and technical expertise to perform correctly than an exercise ECG; however, the results are more reliable. If you have a positive (abnormal) exercise ECG test but a negative (normal) imaging test, then the exercise ECG was a false positive and you will not be sent for further tests. Which noninvasive imaging test you get often depends on the expertise in your local area and whether you have a preference. Nuclear stress testing and echocardiography are more widely used and have been around longer than cardiac MRI or PET.
- Nuclear stress tests (also called thallium, sestamibi, myocardial perfusion imaging)
- Cardiac MRI
The testing and diagnosis section includes descriptions of what each test entails. This is intended as a guide; please note that the exact details and preparation may vary between facilities and depends on the specific type of test you are having.