Heart catheterization (also called cardiac catheterization) is a diagnostic procedure that carefully examines how the heart and its blood vessels function. One or more catheters (tubes designed to enter small openings) are inserted into the organ through a blood vessel in the arm or leg. The procedure gathers information about the pressure, flow, and supply of blood, as well as supplying blood samples and x rays of the heart and surrounding blood vessels.

The primary reason for conducting a heart catheterization is to diagnose and manage suspected cases of heart disease, a frequently fatal condition that leads to 1.5 million heart attacks annually in the United States.

To understand how heart catheterization is able to diagnose and manage heart disease, the basic workings of the heart muscle must be understood. Just as the body relies on a constant supply of blood, so does the heart. The organ...