A detailed test to view blood flow through the heart, would be through a cardiac catheterization or an angiogram where a thin and flexible tube known as a catheter is threaded through an artery, usually in the leg, to the heart arteries. An invisible dye is injected through the catheter and special x-rays will be taken while the dye flows through the coronary arteries, allowing the doctor to study the blood flow through the heart and blood vessels. Due to the nature of the catheterization with the insertion of the tube, it makes the procedure invasive and hence involving risks although they are rare.