What Is an Echocardiogram?

An echocardiogram — commonly called an "echo" — is an ultrasound examination of the heart. It uses high-frequency sound waves to create real-time images of the heart's structure and function, providing information about the heart chambers, valves, wall motion, muscle function, pericardium, and blood flow. The echocardiogram is arguably the single most valuable non-invasive cardiac imaging test — safe, widely available, radiation-free, highly informative, and capable of diagnosing a remarkable range of cardiac conditions.

The Physics Behind Echocardiography

Ultrasound uses sound waves at frequencies above human hearing (typically 2–10 MHz for cardiac imaging). The echocardiography transducer — a hand-held probe placed against the chest — emits brief pulses of ultrasound waves into the chest. When these waves encounter tissue boundaries (between blood and heart muscle, for example), they are partially reflected back to the transducer. The transducer detects these returning echoes and a computer calculates the distance to each reflective surface based on the time it takes each echo to return (since sound travels at a known speed through tissue — approximately 1,540 m/s). By rapidly repeating this process and sweeping across multiple angles, the system reconstructs real-time cross-sectional images of the heart.

The result: a moving ultrasound image that shows the heart beating in real time — each contraction visible, valve movements captured, blood flow color-coded by velocity and direction.