Cardiac CT Angiography
In CT angiography (CTA), computed tomography using a contrast material produces the detailed pictures. CT imaging uses special x-ray equipment to produce multiple images and a computer to join them together in multidimensional views.
Cardiologists use the procedure to: 1) identify disease and aneurysms in the aorta, both in the chest and abdomen, or in other major blood vessels; 2) detect atherosclerosis disease in the carotid artery of the neck, which may limit blood flow to the brain and cause a stroke; 3) detect atherosclerotic disease that has narrowed the arteries to the legs and help prepare for endovascular intervention or surgery; 4) guide surgeons making repairs to diseased blood vessels, such as implanting or evaluating a stent; 5) identify dissection or splitting in the aorta in the chest or abdomen or its major branches; 6) show the extent and severity of atherosclerosis in the coronary arteries; 7) plan for a surgical operation, such as coronary bypass; 8) examine pulmonary arteries in the lungs to detect pulmonary embolism (blood clots from leg veins).
This examination is usually done on an outpatient basis. Though the scanning itself causes no pain, there may be some discomfort from having to remain still for several minutes. If you have a hard time staying still, are claustrophobic or have chronic pain, you may find a CT exam to be stressful. The technologist or nurse, under the direction of a physician, may offer you a mild sedative to help you tolerate the CT scanning procedure. You will be alone in the exam room during the CT scan, however, the technologist will be able to see, hear and speak with you at all times. After a CT exam, you can return to your normal activities. If you received contrast material, you may be given special instructions.
CT angiography is able to detect narrowing of blood vessels in time for corrective therapy to be done. It gives more precise anatomical detail of blood vessels than magnetic resonance imaging (MRI). Compared to catheter angiography, which involves placing a catheter (plastic tube) and injecting contrast material into a large artery or vein, CT angiography is a much less invasive and more patient-friendly procedure. This procedure is a useful way of screening for arterial disease because it is safer and much less time-consuming than catheter angiography and is a cost-effective procedure. There is also less discomfort because contrast material is injected into an arm vein rather than into a large artery in the groin. No radiation remains in a patient's body after a CT examination. There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk. If you have a history of allergy to x-ray contrast material, your radiologist may advise that you take special medication for 24 hours before CT angiography to lessen the risk of allergic reaction. Another option is to undergo a different exam that does not call for contrast material injection. Women should always inform their physician and x-ray or CT technologist if there is any possibility that they are pregnant. Nursing mothers should wait for 24 hours after contrast material injection before resuming breast-feeding. The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare, and radiology departments are well-equipped to deal with them.
A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table. CT angiography should be avoided in patients with advanced kidney disease or severe diabetes, because x-ray contrast material can further harm kidney function. If a patient's heart is not functioning normally, or if there are multiple blocked blood vessels, CT angiograms may be hard to interpret. CT angiograms are not yet as reliable as selective catheter injections (performed after puncture of the artery in the groin) in imaging small tortuous arteries, particularly coronary arteries in the rapidly moving heart.