Coronary angiography is a procedure that uses X-ray imaging to exam the inside of your heart's blood vessels. It's part of a general group of procedures known as cardiac catheterization.

During angiography, dye is injected into the blood vessels of your heart. The dye is visible by X-ray machine. The machine rapidly takes a series of X-ray images (angiograms), offering a detailed peek at the inside of your blood vessels.

Angiography is one of the most useful and accurate tools in diagnosing and evaluating certain cardiovascular problems.

Your doctor may recommend that you undergo coronary angiography if:

• You have symptoms of coronary artery disease, such as chest pain (angina)
• You have unexplained pain in your chest, jaw, neck or arm, and other testing has been inconclusive
• You have new or increasing chest pain (unstable angina)
• You don't have symptoms, but other tests have suggested you may have heart abnormalities
• You're going to have surgery unrelated to your heart, but you're at high risk of having a heart problem during that surgery
• You're planning to have heart valve surgery
• You have congenital heart disease
• You have congestive heart failure
• You have certain other heart or blood vessel problems or certain traumatic chest injuries

Because of its risks, angiography often is done only after certain other heart tests have been performed, such as an electrocardiogram, an echocardiogram or a stress test.

Catheterization refers to any procedure in which a long, thin, flexible plastic tube (catheter) is inserted into your body. Catheter procedures can both diagnose and treat heart and blood vessel conditions. Angiography, which is used for diagnosis, is the most common type of heart catheter procedure. Heart doctors (cardiologists) perform about 1 million each year in the United States.

Other types of diagnostic cardiac catheter procedures are used to:

• Perform a left or right ventriculogram — an X-ray image to measure pumping function
• Measure blood pressure within the heart, lungs and blood vessels
• Assess the amount of blood flow through the heart and blood vessels
• Take a sample (biopsy) of heart muscle
• Measure the amount of oxygen in the blood
• Assess the electrical system of the heart (electrophysiology)

In addition, catheterizations can be used to treat certain heart conditions by:

• Opening clogged arteries using coronary angioplasty
• Closing holes in the heart, such as patent foramen ovale or atrial septal defect
• Opening up narrow heart valves, such as mitral or pulmonary stenosis
• Treating abnormal heart rhythms with ablation procedures
• Placing cardiac pacemakers or defibrillators

Preparation is similar whether you're having coronary angiography or another type of heart catheter procedure. In some cases, these procedures are performed on an emergency basis. More commonly, though, they're scheduled in advance, giving you time to prepare.

Angiography is performed in the catheterization (cath) lab of a hospital. Usually you go to the hospital the morning of the procedure. Your health care team will give you specific instructions and talk to you about any medications you take. General guidelines include:

• Don't eat or drink anything after midnight the day before your procedure.
• Take all your medications to the hospital with you — in their original bottles.
• If you have diabetes, discuss your insulin or oral medication program with your doctor.

Before your angiography procedure starts, your health care team reviews your medical history, including allergies and medications you take. They may perform a physical exam and check your vital signs — blood pressure and pulse. You empty your bladder and change into a hospital gown. You may have to remove contact lenses, eyeglasses, jewelry, hairpins and other items.

An intravenous (IV) line is inserted into a vein in your arm. You may get a sedative through the IV to help you relax, as well as other medications and fluids. A small amount of hair may be shaved from your groin or arm where the catheter is inserted.

The procedure is done in a room that resembles an operating room. You lie on your back on an X-ray table. Because the table may be tilted during the procedure, safety straps may be fastened across your chest and legs. X-ray cameras may move over and around your head and chest to take pictures from many angles.

Electrodes on your chest monitor your heart throughout the procedure. A blood pressure cuff tracks your blood pressure and another device, a pulse oximeter, measures the amount of oxygen in your blood.

Although you may be sedated, you aren't given general anesthesia. Rather, you're awake during the procedure so that you can follow instructions, such as holding your breath at times. You may get medication (anticoagulants) to help prevent your blood from clotting on the catheter and to relax your coronary arteries.

Your health care team washes and disinfects the skin where the catheter will be inserted. The area is numbed with an injection of local anesthetic. A small cut may be made at the catheter site. A small needle is placed in your blood vessel and a tiny wire is threaded in place. The needle is removed and a short plastic tube (sheath) is inserted into your artery or vein.

The catheter is inserted through the sheath and into your blood vessel. It's then carefully threaded to your heart or coronary arteries under guidance of an X-ray machine that shows real-time images of your body.

Threading the catheter shouldn't cause pain, and you won't feel it moving through your body. Tell your health care team if you do experience any discomfort.

Dye is injected through the catheter, and the X-ray machine takes angiograms of your heart and blood vessels. You may have a brief sensation of flushing or warmth when the dye is injected. Don't be alarmed if you feel your heart skipping beats — that's a normal occurrence during angiograms. But again, tell your health care team if you feel pain or discomfort.

You may be asked to take deep breaths, hold your breath, cough, or place your arms in various positions, or your table may be tilted.

The catheter may need to be moved several times, and more dye injected. Depending on what your doctor discovers during the angiography, you may have additional catheter procedures at the same time.

The angiography itself takes about one hour, although it may be longer, especially if combined with other heart catheter procedures. Preparation and post-procedure care can add several more hours.

When the angiography is over, the catheter may or may not be removed from your arm or groin. You're taken to a recovery area for observation and monitoring. When your condition is stable, you return to your own room, where you're monitored regularly.

The plastic sheath that was first inserted into your blood vessel may be removed immediately. Your doctor may use a patch, clamp, manual pressure or stitches to close the blood vessel.

Alternatively, the sheath may be left in place for several hours or even overnight. If you received anticoagulants during the procedure, removing the sheath too soon could trigger heavy bleeding.

In either case, as long as the sheath is in, remain still. Even after the sheath is removed, you may have to lie still several more hours — your health care team will tell you precisely how long. During this time, pressure may be applied to the puncture site to prevent bleeding and promote healing.

Drink plenty of fluids to help flush the dye from your body. If you're feeling up to it, have something to eat. You may be discharged the same day, or you may have to remain in the hospital for a day or more.

Ask your health care team when you can bathe or shower, when you can return to work and when you can resume other normal activities. Avoid strenuous activities and heavy lifting for several days.

Your puncture site is likely to remain tender for several days. It may be slightly bruised and have a small knot (hematoma).

Call your doctor's office if:

• You develop increasing pain or discomfort at the catheter site
• You have signs of infection, such as redness, drainage or fever
• There's a change in temperature or color of the leg or arm that was used for the procedure
• You feel faint or weak
• You develop chest pain or shortness of breath

If the catheter site is actively bleeding or begins swelling, apply pressure to the site and contact emergency medical services.

Angiography is a diagnostic tool. That is, it shows doctors what's wrong with your blood vessels.

It can:

• Show how many of your coronary arteries are blocked by fatty plaque accumulations (atherosclerosis)
• Pinpoint where blockages are located in your blood vessels
• Indicate the extent of blockages
• Evaluate the results of previous coronary bypass surgery
• Assess blood flow through your heart and blood vessels

Knowing this can help your doctor determine your best course of treatment and how much danger your heart condition poses to your health. Based on your results, your doctor may decide, for instance, that you would benefit from having coronary angioplasty to help unblock clogged arteries.

As with most procedures done on your heart and blood vessels, coronary angiography does pose some risk. Major complications are rare, though. Among the potential risks and complications are:

• Heart attack
• Stroke
• Trauma to the catheterized artery
• Irregular heart rhythms (arrhythmias)
• Allergic reactions to the dye or medication
• Perforation of your heart or artery
• Kidney damage
• Excessive bleeding
• Infection
• Blood clots
• Radiation exposure from the X-rays

You may want to talk to your doctor about the availability of emergency cardiac surgery facilities where you're having the angiogram.

Although angiography remains the gold standard for assessing coronary arteries and coronary blood flow, other imaging techniques are rapidly improving and expanding.

For instance, computed tomography (CT) imaging is now used to provide detailed pictures of the heart arteries, enabling less invasive early detection of plaque formation. Although CT imaging still requires the use of intravenous needles, it doesn't require catheterization within the heart, reducing risk. The major disadvantage of CT imaging is that it can't actually treat the heart conditions it uncovers.

Another technique gaining in popularity is magnetic resonance angiography (MRA), which is similar to the more familiar magnetic resonance imaging (MRI). MRA produces detailed images of your heart and blood vessels without the use of catheters or X-rays, although contrast dye generally is used. MRA works by using radio waves in a strong magnetic field to produce data that a computer turns into detailed images of tissue slices. This technique can be used to assess heart function and to diagnose congenital heart disease. It can't be used to treat heart problems. And if you have a pacemaker or implanted defibrillator, you can't have an MRA.