What is a contrast angiogram?
A contrast angiogram is a diagnostic test that produces an X-ray movie of the blood vessels and the blood flowing through them. It is considered the “gold standard” test for diagnosing artery disease and determining how widespread and severe the narrowing or blockages are.
Unlike other imaging tests used to diagnose PAD, a contrast angiogram requires entering the body. To perform the test, a long, thin tube called a catheter is inserted into an artery in your groin or arm and guided to the area to be studied. The catheter is used to inject a dye into the blood vessels, and the dye is filmed by an X-ray camera, producing an angiogram an X-ray movie of your vessels as the blood moves through them.
Contrast angiograms are used to investigate many types of artery disease, including:
- PAD in the legs
- Kidney artery disease
- Carotid (neck) artery disease
Who might have a contrast angiogram?
The contrast angiogram is considered the gold standard test for looking at the anatomy of the arteries and blood flow through them. However, it has mostly been replaced by less-invasive imaging tests (such as duplex ultrasound, CT angiogram, or MRA) to diagnose PAD and get more information about the extent and location of blockages. Unlike other imaging tests, a contrast angiogram requires entering the body to inject the dye and therefore carries a small risk of artery damage and other complications. In some cases, a contrast angiogram may be used to diagnose kidney artery disease after other tests were inconclusive.
A contrast angiogram is usually reserved for women who are considering a procedure to treat PAD, such as angioplasty and stenting or lower extremity bypass surgery. The angiogram images help doctors determine which procedure may be best for you and develop a plan to treat the blockages. In some centers, a contrast angiogram is regularly performed in patients who are considering such procedures. In others, the contrast angiogram is replaced by less-invasive tests whenever possible.
During procedures to restore blood flow to vessels blocked by PAD (such as angioplasty and stenting), a contrast angiogram is usually used to guide the treatment as it is being done. Because the treatment itself already involves introducing instruments into the body, the additional risks of the angiogram test are considered negligible.
Women with aortic disease who plan to undergo an aortic aneurysm repair may have a contrast angiogram to provide a detailed view of the aorta. Other less-invasive tests are used to diagnose aortic disease and monitor the size of the aneurysm and the outcome of treatment.
Left: A contrast angiogram of the iliac arteries in the lower abdomen.
Right: The angiogram location shown on a woman’s body.
How do I prepare for the test?
Before the test, you will need to remove all clothing and jewelry and put on a hospital gown. You may be asked not to eat or drink in the 4 to 8 hours before the procedure. You will be asked about your medical history and given blood thinning drugs to prevent clots during the procedure.
Before you have the test, be sure your doctor knows if you:
- Are allergic to any medications
- Are allergic to the dye used in the test
- Have ever had a serious allergic reaction (anaphylaxis) to any substance
- Have diabetes, especially if you are taking the drug metformin (Glucophage)
- Have a history of bleeding problems or are taking blood-thinning drugs
- Have a history of kidney problems
- Have asthma
- May be pregnant
- Are breastfeeding (you should not resume doing so until the dye has been cleared from your body, 24 to 48 hours)
Talk to your doctor about any medications or dietary supplements that you are taking because they may affect the accuracy of the test. You may have to stop taking or reduce the dosage of certain medications, particularly blood-thinning medications (such as aspirin or warfarin).
What happens during the test?
You will change into a hospital gown. The test will take place in a specialized catheterization lab; the staff wear hospital gowns and masks, and the lights are dimmed.
You will be hooked up to an ECG so that your heart rate can be monitored small sticky patches with wires attached will be taped to your chest. Your blood pressure will also be monitored. The physician will insert an intravenous (IV) line into your arm, so that a mild sedative and other medications can be given. You will feel the needle prick when the IV is inserted.
The catheter will be inserted into the femoral artery in your groin the crease where your leg meets your pelvis. First the area will be cleaned, shaved, disinfected, and numbed with a local anesthetic. A small cut will be made and an introducer sheath will be placed in the opening. The sheath is a short hollow tube through which the catheter is fed into the artery. The catheter is steered over a wire through your arteries until it is close to the affected arteries, using X-ray images as a guide to make sure it is properly placed. You will probably feel a warm sensation when the contrast dye is injected into the catheter. As the dye circulates in your blood, a series of X-ray pictures is taken.
After the test, the catheter is removed and pressure is applied at the insertion site to stop the bleeding. There are two techniques for removing the introducer sheath where catheter was inserted. The more traditional method is to wait 4 to 6 hours for the effects of the blood thinners to wear off, then to apply pressure while removing the sheath. A newer technique uses a small device that makes a tiny seal or stitch in the artery to close it off. The advantage of this is that there is no need to wait for the blood thinners to wear off.
The angiography procedure typically takes less than an hour, but may take longer for complex cases. Some patients will be able to leave the same day, but you may need to remain in the hospital overnight for observation and to make sure the insertion site heals properly.
What happens after the test?
When the procedure is complete, you will be transferred to a recovery room. You may feel groggy from the sedative, and the catheter insertion site may be bruised and sore. You will be instructed to lie in bed with your legs out straight. While you are in the recovery room, the place where the catheter was inserted will be checked for bleeding and swelling and your vital signs will be continuously monitored. You should drink plenty of fluids to flush out the contrast dye.
You may be released from the hospital on the same day or the next day. Your doctor will give you instructions on how to make sure you have no further complications: these usually include no strenuous physical activity for a day or two.
Some soreness is common during the first week, and bruising (when it happens) can take as long as 3 weeks to heal. Be sure to alert your doctor if you feel numbness or have problems moving your leg, if you develop a fever, or if the area where the incision was made begins bleeding or shows signs of infection such as pain, swelling, warmth, or redness.
You should have a follow-up visit with your doctor within two weeks that includes a physical examination and tests to see how well your kidneys are working to detect any delayed complications of the test.
What do the results mean?
A normal contrast angiogram test result will show that the anatomy of your arteries is normal, the dye flows smoothly through the vessels, and there is no narrowing, blockage, or bleeding. Abnormal results are areas where the dye flows slowly or not at all, indicating that the vessel is narrowed or blocked by blood clots or fatty buildup on the walls of the arteries.
The results of a contrast angiogram can be used to decide whether you need a procedure to clear the blockages such as angioplasty or lower extremity bypass surgery, and to determine which treatment is best for you.
What are the risks of the test?
Contrast angiography is a very safe procedure. However, because it involves introducing a foreign object (the catheter) into the arteries, the test carries a small risk of complications including damage to the arteries, blood clots, infections, and bleeding where the catheter was inserted. The contrast dyes used in catheterization can also cause kidney damage in women with diabetes or kidney disease.
Although it occurs in fewer than 1 in 1000 people undergoing the test, some people have an allergic reaction to the dye used in the procedure. Be sure to tell your doctor ahead of time if you have experienced this in the past medication can be given during the procedure to minimize this problem.
Since it uses X-rays to produce an image, the contrast angiogram test involves radiation. The amount of radiation you are exposed to during diagnostic tests is considered safe, and the technicians are trained to minimize your radiation exposure.
How does the angiogram compare with other tests for PAD?
Click here for a quick comparison of the contrast angiogram with other imaging tests used to diagnose and evaluate PAD.
A contrast angiogram is the most accurate test for looking at the anatomy and blood flow in the arteries in women who are considering a procedure to treat PAD, and it remains the “gold standard” test to which all other tests are compared. However, for many uses, including diagnosing the location and severity of PAD and planning treatments, other tests such as CT angiography and MRA provide detailed images without the risks of an invasive procedure.
The contrast angiogram remains the only accepted imaging test for guiding procedures to treat artery disease as they are being performed.