What does an echocardiogram show that an X-ray doesn't?

The echocardiogram is an ultrasound of the heart. An x-ray is a two-dimensional view or picture of the heart or of the chest. In contrast, the echocardiogram is a more specialized view of the heart; it can detect the heart's motion and look at chamber sizes and blood flow through the heart.

While X-rays are excellent for aiding in diagnosis as they give us an idea of the general shape and size of the heart, an echocardiogram lets us look into the heart to see how the valves and chambers are structured. It can reveal changes that might not be picked up on an X-ray, so it's a very valuable tool for diagnosis.