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Angiography is an X-ray procedure used to visualize blood vessels (both arteries and veins) after they have been injected with a contrast medium. Blood vessels cannot be seen on X-ray film unless they have been injected with a radiographic contrast medium. When an angiogram is used to examine arteries, it is known as an arteriogram. In studies of the arteries, the contrast medium is most commonly injected through a catheter inserted into an accessible artery (such as one in an arm or a leg) and then threaded into the artery to be studied. For example, in a coronary angiogram, a catheter may be inserted into the femoral artery of the leg and threaded upward into the coronary artery. When an angiogram is used to examine the veins, it is called a venogram. Venograms generally involve the veins deep in the lower legs.
Why It Is Performed
Angiography is generally used to detect abnormalities of the blood vessels or to evaluate the blood supply to various organs. The procedure may yield information about blood flow, the formation of an aneurysm (an abnormal ballooning of a weakened area in a wall of an artery), vascular anomalies, tumors and hemorrhage. Deep leg veins may be examined by angiography to confirm the presence of deep-vein thrombosis, identify causes of edema, and assess vascular health after surgery. Cardiac catheterization is a type of angiography that involves threading a catheter through a blood vessel until the catheter reaches the heart. The procedure is done so that the coronary arteries and other structures can be visualized. Catheterization can also be used to visualize the blood vessels of the legs, brain, liver, spleen, kidneys and intestines. Because angiography carries the risk of complications and is costly, it is generally used when other types of examinations have failed to provide information a physician needs to know. In some cases, angiography may be the only procedure that can yield the necessary information.
How It Is Performed
Angiography can be performed as an outpatient procedure in a hospital. The person being examined lies on a movable table and is given intravenous sedatives to relax him or her. Heart rate and oxygen levels are monitored throughout the procedure. A local anesthetic is applied to the area, a needle is inserted into an accessible blood vessel, and a guide wire is threaded through the needle. A very thin, flexible tube called a catheter is inserted over the guide wire and passed directly into the artery or vein. The catheter is then manipulated until it is in the desired location. Contrast medium is injected into the catheter, causing a mild sensation of warmth. The normal flow of blood carries the contrast medium to the selected blood vessels. As the contrast medium moves through the blood vessels, X-ray images are taken rapidly. The entire procedure usually takes between one and two hours. The catheter is removed, and pressure is applied over the puncture site for 10 to 15 minutes. The person who has undergone angiography must remain in bed for up to six hours after the procedure to allow the puncture site to heal to prevent bleeding. Normal activity must be limited for 24 hours, and vigorous activity must be avoided for up to 72 hours.
Risks
Excerpted from: Complete Medical Encyclopedia, American Medical Association, 2003.