How does an angiogram work?
An angiogram works similar to an x-ray. The body casts a “shadow” on film when it is exposed to the x-ray, much like when you hold a flashlight up to your hand and cast a shadow on a wall. Normally your blood vessels cannot be seen in an x-ray, but adding a dye (contrast agent) into the blood stream makes your arteries and veins visible. Contrast agent contains iodine, a substance that x-rays cannot pass through.
To deliver the contrast agent, a catheter is advanced from the femoral artery in the leg to one of the four arteries in the neck that lead to the brain. The doctor steers the catheter through the blood vessels while watching a monitor. A fluoroscope machine, called a C-arm is an arc shaped piece of equipment that generates x-rays from one side and photography them on the other side. Contrast is injected into the bloodstream to make the blood vessels visible on the monitor. The result is a kind of roadmap of the arteries.
Today many catheter angiographic studies have been replaced by less invasive methods such as computed tomography angiography (CTA) and magnetic resonance angiography (MRA) that do not require a catheter be inserted. Catheter angiography has the benefit of combining diagnosis and treatment in patients who may undergo surgery or other endovascular procedures such as angioplasty, aneurysm coiling, or stent placement.
What does an angiogram show?
Angiograms are very good at detecting problems with blood vessels such as an aneurysm, arteriovenous malformation (AVM), artery stenosis from plaque build-up, tumors, and clots.
Who performs the test?
A doctor who specializes in interventional radiology will perform the test in the angiography suite of the radiology department.
How should I prepare for the test?
Don’t eat or drink after midnight the night before the test. You should take your normal morning medication with a small amount of water. Make arrangements to have someone drive you to and from the hospital. Before the test, you will be asked to change into a hospital gown and an intravenous (IV) line will be placed in your arm. The radiologist or nurse will discuss the test with you, explain the risks, answer any questions, and have you sign consent forms.
What happens during the test?
Step 1: prepare the patient
You will like on your back on an x-ray table. Your head is positioned so that it will not move during the test. Your blood pressure and heart rate will be monitored throughout the test.
Step 2: insert the catheter
The catheter is usually inserted into the femoral artery in the groin, however other arteries may be chosen. The inner thigh and groin area is first shaved and cleansed. A local numbing agent is given to minimize discomfort as a skin incision is made. The femoral artery is located and a hallow needle is inserted into the artery. Next, a long guide wire and flexible catheter are passed through the needle to ender the bloodstream. A special dye, called a contrast agent, is injected into the blood stream through the catheter. The dye makes the blood vessels visible on the x-ray monitor (fluoroscope). Watching the monitor while injecting dye, the doctor carefully guides the catheter from the femoral artery in the leg, up the aorta, past the heart, and to one of the four arteries in the neck that lead to the brain. You may feel brief discomfort when the catheter is inserted, but most catheter manipulation is painless.
Step 3: take x-ray pictures
When the catheter is placed correctly, the doctor injects the contrast agent while x-ray pictures are taken. You may feel a hot, flushed sensation that lasts 5 to 20 seconds. At this point you should remain very still so that the x-ray images will not be blurred. This may be repeated several times in order to view all necessary arteries.
Step 4: remove the catheter
Once the x-rays have been taken, the catheter will be removed and pressure is applied to the puncture site for 10 to 15 minutes so that your artery will not bleed. A bandage may be tightly applied.
What happens after the test?
You must stay on your back in bed for the next 6 hours, keeping your bandaged leg as straight as possible. If an angio-seal was used, you must remain flat on your back for only 2 hours. You may feel a pea-size lump in your groin or mild tenderness at the this site. Notify the nurse if any pain, swelling, or bleeding occurs at the incision site.
Discharge instructions
Discomfort
- A pea-size lump in your groin or mild tenderness and bruising at the incision site is normal. You may take ibuprofen and apply a warm compress for discomfort.
- Mild headache can develop after the procedure. Drink plenty of fluids, especially water over the next few days; this will help flush out the contrast dye.
Activity
- Do not drive for 3 days after the procedure or until discussed with your doctor.
- Do not lift anything heavier than 10 pounds (e.g., gallon of milk) for 3 days.
Bathing/incision care
- You may shower 24 hours after the procedure. No baths, hot tubs, or swimming for 3 days.
- Remove the bandage before showering. Gently clean the site using soap and water. Dry thoroughly and apply a new bandage. If steristrips are in place, allow them to fall off on their own.
- Check for signs of infection such as swelling, redness, yellow or green discharge, warm to the touch.
- Keep your dressing clean and dry. Change the dressing daily. Wash your hands before and after. Do not apply creams, lotions or ointments on or near your incision.
- If bleeding occurs at the puncture site, lie down and apply firm pressure.
- If you received an angio-seal to close the artery puncture site, the body will absorb the collagen plug in about 60 to 90 days. During this time, carry your patient information card with you at all times.
When to call your doctor
- If you temperature exceeds 101.5°F or if the incision begins to separate or show signs of infection, such as redness, swelling, pain or drainage.
- Go to the nearest emergency room if you experience a large swelling or sudden pain at the puncture site, or loss of sensation numbness or swelling of the leg.
What are the risks?
An angiogram is an invasive test, so it is not without risk. There is a very small risk of the catheter damaging your artery or loosing a piece of plaque lining the artery wall. The loose piece of plaque can travel up the artery into the brain and could block blood flow causing a stroke.
Some people are sensitive to the contrast agent used. The most common side effects from the iodine contrast are brief metallic taste in your mouth and a feeling of warmth throughout your body.
An extremely rare reaction occurs when you experience severe hives and have difficulty breathing. Medications such as antihistamines can reverse this reaction. If you have diabetes or kidney problems you may experience kidney failure, but this too is extremely rare.
Be sure to tell your doctor if you are pregnant or have a history of allergies (to medications, previous iodine injections, or shellfish), diabetes, asthma, a heart condition, kidney problems, or thyroid conditions. Also tell them if you take any blood thinning medication such as aspirin or Coumadin.
How do I get the test results?
The radiologist will promptly review your images and communicate directly with your referring physician, who in turn will discuss the results with you.
If you have any questions, please contact your provider that has ordered the angiogram for you.