How coronary artery disease (CAD) is diagnosed
There are a number of tests that can be used to help diagnose CAD, including EKGs, echocardiograms, and stress tests. Your doctor may start by asking you about your family and medical history and performing a physical exam. To make an accurate diagnosis, he or she may order one or more of the following tests:
- Blood tests: Analyzing blood samples can check your levels of cholesterol, sugar, and proteins. High levels of a substance called C–reactive protein in the blood can indicate inflammation that may raise the risk for CAD.
Stress tests: Stress tests can help your doctor determine how well your heart works when it's under stress. This test can show potential signs of CAD, including changes in heart rhythm, electrical activity, heart rate, and blood pressure. There are several types of stress tests.
- –Exercise stress test—In this test, the most common stress test, your heart rate is measured by an electrocardiogram (EKG) (see below) while you walk or run on a treadmill or ride a stationary bike.
- –Nuclear stress test—This can provide information on parts of the heart that don't function normally. Using a radioactive tracing material that is injected into your bloodstream, this test is performed by comparing two pictures of your heart—one when the heart is stressed, and one when the heart is at rest. This test can show potential signs of CAD, including changes in heart rhythm, electrical activity, heart rate, and blood pressure. This procedure is used with an exercise stress test or a stress medication if you are unable to exercise to the level necessary to complete the test. The medication simulates the effects of physical activity by increasing blood flow to your heart. Here's how these tests work:
- Nuclear stress test with exercise: You walk on a treadmill or pedal a stationary bike, and the tracer is injected into your bloodstream.
- Nuclear stress test with a pharmacologic agent: You lie down and a pharmacologic agent (a medication) is injected through the IV, followed by the tracer.
- Chest X-ray: This creates an image of the heart and lungs, which can help your doctor diagnose heart disease.
- Electrocardiogram (EKG): An EKG measures the electrical activity of your heart. This can tell your doctor if you have a regular heartbeat and how fast it is.
- Resting EKG: You lie on a bed or table and electrodes (small metal discs) are attached to the skin of each arm and leg and your chest. These are attached to a machine that traces the activity of your heart as you lie still.
- Echocardiogram: This test uses ultrasound to create a picture of the size and shape of your heart and review how well it's working. An echocardiogram can detect restricted blood flow in areas of the heart.
- Computed tomography (CT) scan: A CT scan uses an X-ray machine to take detailed pictures of the heart and create a 3-D image of the entire heart. This test looks for CAD or other heart problems.
- Holter monitoring: Electrodes are attached to your chest and to a small recording monitor. The monitor is worn for 1 to 2 days and records your heart’s rhythms. You also write down your activities while you wear the monitor. Your doctor will check the records to see if you’ve had irregular heart beats.
- Positron emission tomography (PET) scan: A small amount of radioactive material is injected and a scanner takes pictures of the heart. This is used to detect CAD and other types of heart disease.
- Cardiac MRI: Cardiac MRI (magnetic resonance imaging) uses a computer, radio waves, and magnets to create pictures of your heart. This can help detect CAD and other types of heart disease.
If your doctor suspects you have CAD, he or she may recommend that you have additional tests, which may include the following:
- Coronary angiography: This procedure takes X-ray images while a dye is injected into a coronary artery, and monitors the blockage and flow of blood through the heart.
- Cardiac catheterization: In this procedure, a long, thin, flexible tube called a catheter is inserted into a blood vessel in your arm, groin, or neck and threaded into your heart. Through this catheter, doctors conduct diagnostic tests and administer certain treatments. Ultrasound is often used during cardiac catheterization to detect blockage to the coronary arteries.