Cardiac angiography is mainly used to diagnose coronary atherosclerotic heart disease and is the gold standard for the diagnosis of coronary heart disease. The specific steps are to insert the contrast catheter under the angiography machine through the femoral artery of the lower extremity or the radial artery of the arm, retrograde along the aorta to the root of the ascending aorta, explore the left or right coronary artery opening for insertion, and inject the contrast agent to visualize the coronary arteries. Coronary angiography can clearly show the entire left or right coronary trunk and its branch vessels to visualize whether there is stenosis in the coronary arteries, as well as the degree and extent of stenosis.