Used with or without exercise, echocardiography can assess how the heart works. Using sound waves to generate an image, a cardiologist can evaluate many aspects of the heart. Echocardiograms can examine the structure of the heart including the heart valves, the thickness of the heart muscle, the septum (the tissues that separate the four heart chambers from each other) and the pericardial sac (the outside lining of the heart).
The test can indirectly assess blood flow to parts of the heart muscle. If there is decreased blood flow, then segments of the heart wall may not beat as strongly as adjacent heart muscle. These wall motion abnormalities signal the potential for coronary artery disease.
The echocardiogram can also assess the efficiency of the heart by measuring ejection fraction. Normally when the heart beats, it pushes more than 60% of the blood in the ventricle out to the body. Many diseases of the heart, including coronary artery disease, can decrease this percentage (the ejection fraction).
Radioactive chemicals like thallium or technetium can be injected into a vein and their uptake measured in heart muscle cells. Abnormally decreased uptake can signify decreased blood flow to parts of the heart because of coronary artery narrowing. This test may be used when the patient's baseline EKG is not normal and is less reliable when used to monitor a stress test.
The latest generation of CT scanners can take detailed images of blood vessels and may be used as an adjunct to determine whether coronary artery disease is present. In some institutions, the heart CT is used as a negative predictor. That means that the test is done to prove that the coronary arteries are normal rather than to prove that the disease is present.