Echocardiogram is a test that uses ultrasound waves to generate images of the heart, including its chambers and valves and the surrounding structures. Echocardiography can measure cardiac output and can identify fluid around the heart, known as a pericardial effusion. An echocardiogram also can reveal abnormal anatomy or infections of the heart valves.
Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.