A cardiac catheter is a type of catheter inserted into a vessel or chamber of the heart during a diagnostic procedure known as cardiac catheterization, according to WebMD. The catheter is a flexible thin tube that is inserted by a doctor to check the blood flow in the coronary arteries leading to the heart. It may also be used to check for genital heart defects in children.
Cardiac catheterization checks the functionality of the heart's various structures, including the all of the heart, its valves and the heart chambers, notes WebMD. It may be used to determine the presence of coronary artery disease, which causes calcium deposits and fat to build up inside the coronary arteries, making them narrow and resulting in inadequate blood flow to the heart.