The process of taking a photo or movie with the help of X-ray, after injecting day (a specific type of radio opaque chemical) in any artery is known as angiography. The angiography of arteries supplying blood to the heart (coronary arteries) is known as coronary angiography.
This is a test to define the adequacy of blood supply to the heart. Several additional important information such as presence of block or obstruction, percentage narrowing created in the diameter of the artery, presence of calcium or blood clot in that block, etc. can be obtained with the help of angiography. Based on the symptoms of the patient, information obtained through angiography and some other important considerations, an expert cardiologist recommends further line of treatment. Whether a patient needs angioplasty or bypass surgery for coronary blockages is known only after angiography is done.