First used in the early 1950s, angiography is now a standard procedure to locate areas where an artery is closed or constricted and interfering with the circulation of blood.
Angiography applied to the heart is called coronary angiography. A constriction of one of the arteries feeding the heart can be serious enough that a person will experience chest pains when he or she exercises because the heart muscle has an insufficient supply of blood.
The heart is a special muscular organ that must continue beating at all times. When you are awake or asleep, resting or exercising, the heart must supply the body with blood. In times of extra need, as when you run or bicycle rapidly, the heart must work harder to supply oxygen-laden blood to the muscles. To accomplish its work, the heart is given the first arteries that branch off the main artery leaving the heart, the aorta. In this way the heart has a source of blood at high pressure and with the most oxygen.
The arteries that supply the heart muscle are called the coronary arteries, and they course around the outside of the heart to carry blood to all parts of the hard-working muscle. As a person ages, however, these coronary arteries may begin to close down from cholesterol deposits, or they may have spasms in the muscle of the arteries, or a blood clot that has been circulating in the blood stream may lodge in one of the arteries. Any of these situations can result in pain or even death because the heart muscle is receiving too little oxygen. Pain in the chest caused by an oxygen-starved heart is called angina. Angina is a serious condition requiring medical attention. It may indicate a blockage that is easily controlled by medications, or it may be a life-threatening blockage requiring bypass surgery to restore circulation. To treat angina, the physician must know the exact location of the blockage, whether only one artery is blocked or if several are affected, and how severe the blockage is—whether it is only partially obscuring the artery or entirely plugging the blood passage.
To locate a blockage and discern its severity the doctor usually must resort to an angiogram. This is called an invasive study because it requires a catheter to be inserted into one of the patient's arteries.
To perform an angiogram the cardiologist inserts a long, thin tube (a catheter) into an artery usually in the thigh. The patient is fully awake during an angiogram, which is performed under local anesthesia. In this way the patient can turn over or from side to side if the doctor needs a different view. The arteries do not sense pain or touch, so the patient cannot feel the catheter as it progresses through the arteries.
The catheter is radio-opaque, that is, it can be seen on an x ray so the doctor can follow the progress of the catheter. He feeds the catheter into the artery and from there into the main artery of the body, the aorta. The tip of the catheter is slightly bent so that it can be steered from one artery into another by turning the catheter. The doctor follows the progress of the catheter on a fluoroscope. The fluoroscope is a screen onto which x rays are projected after they pass through the patient. The radio-opaque catheter shows up on the screen as a long, moving shadow.
The physician guides the tip of the catheter from the aorta into the main coronary artery and injects a contrast medium. This is a liquid that also is visible on x rays. As the contrast medium floods through the coronary arteries a videotape is made of the progress of the fluid into and through the arterial tree. The contrast medium is visible only for a few seconds on the fluoroscope and then is pumped out of the arteries, but the videotape can be reviewed at a slower pace. Angiography provides a method to visualize vessels in a given time frame following the distribution or dispersal of the dye through arterial or venous phases. Any constriction or stoppage in the artery will be evident by looking at the pattern of the medium. It will show the artery coursing over the heart until the contrast medium reaches a constriction, where it is pinched into a small stream, or a stoppage, which the medium is not able to pass at all. The physician can move the tip of the catheter to position it at another artery as needed. Computerized enhancement techniques are utilized to improve the resolution of angiograms.
Once the troublesome area or areas have been located the doctor can decide what form of treatment is most appropriate.
A coronary angiogram is a form of test generally called an arteriogram, which means literally a picture of an artery. Arteries are long tubes with muscular walls that carry blood away from the heart. The arterial muscle enables the size of the artery to be enlarged or reduced in accordance with the demand for blood. Immediately after a meal, for example, the arteries to the digestive organs are enlarged to carry away the digested nutrients. The arteries in the arms and legs will be constricted to carry less blood. On the other hand, when a person runs or plays actively the arteries to the arms and legs and other muscles used in the activity are dilated to carry a full load of oxygen-rich blood to the muscles; the arteries to the digestive system are constricted.
Arteriograms are used to see the arteries in organs other than the heart. This diagnostic study can be carried out with the arteries in the brain, to find the location of a ruptured artery that has caused a stroke, for example; or in the kidneys and in the legs. There are variations of arteriograms, a splenoportograph, involves the injection of contrast medium directly into the spleen to view the splenic and portal veins. In all cases the test consists of injecting a radio-opaque contrast medium into a suitable blood vessel and then capturing the image of the arteries made visible by the medium.
See also Circulatory system.
PM Medical News 21st Century Complete Medical Guide to Heart Disease, Heart Attack, Cholesterol, Coronary Artery Disease, Bypass Surgery, Angioplasty New York: Progressive Management Medical News, 2002.