This is an abbreviated version of the complete article.*
Computed tomography angiography (CTA) combines computerized tomographic (CT) scanning (sometimes call CAT scan) with dye that is injected to diagnose narrowing in the coronary arteries, which feed the heart.
CTA is less invasive than conventional angiography.
CTA takes a series of still images that are reconstructed or joined together to produce a 3-dimensional likeness of the area being examined.
Computed tomography angiography (CTA) combines computerized tomography (CT) scanning and angiography to help physicians diagnose problems such as narrowing in the arteries. CT scanning, sometimes referred to as CAT scanning, uses x rays and computers to create detailed images of the internal structures of the body. These images, known as CT scans, show cross-sections, or slices, of the body. CTA is painless and uses a newer form of CT scanning called spiral scans, which is faster than conventional CT scanning, and produces a 3-dimensional (3D) likeness of the area being examined.
CTA helps physicians diagnose blockages in the arteries in two ways. When contrast material is used, CTA can indicate arterial stenosis. Without the use of contrast material, CTA can detect calcium deposits in arteries, which is an indication of atherosclerosis.
CTA is useful in patients who:
Have no coronary heart disease (CHD) symptoms but are at high risk for developing the condition;
Have unusual symptoms but are at low risk for developing CHD; or
Have had inconclusive stress testing.
Patients are instructed to avoid food and liquids 4 to 6 hours before the test and to remove any jewelry and other metal objects, such as hair clips, which interfere with imaging equipment.
Contrast material carries a slight risk of causing an allergic reaction. Patients who know that they have an allergy to contrast material or dye should tell the physician before the contrast material is administered.
Patients who may be unsuited for CTA include those who:
Have an allergy to contrast dye;
Have unstable vital signs; and
Have significant problems with kidney function.
WHAT TO EXPECT
The patient lies still on the scan table that slides into the gantry, the donut-shaped device that houses the scanning equipment.
The patient is given the contrast material through a needle or catheter in the arm. Patients with a rapid heart rate or atrial fibrillation may be given a type of drug called a beta-blocker to slow the heart rate, allowing for a clearer image.
An x ray tube slides around the gantry, passing narrow beams of x rays in an arc over the body. These beams reflect onto an x ray detector positioned opposite the x ray tube. After one arc, the scanning table moves forward a certain distance and the tube transmits another arc of x rays.
The x ray detector transmits the x ray energy to a computer, which transforms the information about the reflected energy into an image.
A medical technician operates the scanning machine from another room. The technician may instruct the patient through an intercom not to move or swallow at certain times during the test to ensure that the images are clear.
The patient will receive the results after a physician who specializes in images of the body interprets the scans.
There are no restrictions on a patient after a CTA. Patients can resume normal activities immediately.
Patients are asked to drink fluids following the test for hydration and to speed excretion of the contrast agent.
Patients who received a sedative should arrange for a ride home after the procedure.
Complications are rare, but may include allergic reaction to the contrast material or kidney problems, especially in patients with diabetes.
Medical Review Date: August 3, 2009
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