The term "angiography" refers to "pictures" of the heart. These pictures can also reveal the structure of the heart and the pressure and flow of the blood through the blood vessels supplying the heart. The procedures are carried out using cardiac catheterization and injection of a contrast dye. The contrast dye is called "radiopaque" because it can be seen on x-ray film. In angiographic procedures, the dye permits the doctor to see moving, real-time x-ray images of the heart on a fluoroscope screen while the test is being performed.

One of the tests angiography provides is a study of blood flow and pressures in the heart chambers and blood vessels leading into and away from the heart. Called a hemodynamics study, it evaluates blood flow, pressure and cardiac output. During this evaluation, the catheter is positioned in a heart chamber or one of the "great" vessels of the chest. Specific measurements that can be obtained with this technique include:

• pressure changes in the heart chambers during each cardiac cycle or heartbeat

• the location and degree of any resistance to flow through the valves or blood vessels

• the amount of blood that is pumped out of the left ventricle during each cardiac cycle

Another angiographic study is coronary arteriography, which is currently the most authoritative test for coronary artery disease. Coronary arteriography involves injection of the radiopaque dye into the aorta and the coronary circulation, the arteries that supply blood to the heart muscle. X-ray pictures, called coronary arteriograms, are taken as the dye travels into the coronary arteries and show how well the dye passes into and through each vessel. Any narrowing of a vessel or obstruction to the flow of dye can be documented for the doctor’s evaluation. This information may include:

• Number of vessels affected by narrowing or obstruction

• Location of narrowing or obstruction

• Severity of obstruction