A coronary angiogram is a procedure that uses X-ray imaging to see your heart's blood vessels. Coronary angiograms are part of a general group of procedures known as heart (cardiac) catheterization.Heart catheterization procedures can both diagnose and treat heart and blood vessel conditions. A coronary angiogram, which can help diagnose heart conditions, is the most common type of heart catheterization procedure.During a coronary angiogram, a type of dye that's visible by an X-ray machine is injected into the blood vessels of your heart. The X-ray machine rapidly takes a series of images (angiograms), offering a detailed look at the inside of your blood vessels. If necessary, your doctor can perform procedures such as an angioplasty during your coronary angiogram.