Cardiac CT Angiography

Why are you being sent for a Cardiac CTA?

A Cardiac CTA or Coronary CTA is a non-invasive imaging test utilizing a CT scanner with iodinated contrast and sophisticated 3D reconstruction software to evaluate the coronary arteries for fatty deposits or calcium deposits that may lead to blockages formed by cholesterol plaque.  If left untreated, these areas of build-up, called plaques, can cause fatigue, shortness of breath, chest pain and/or heart attack.  For various electrophysiological procedures (EP) such as atrial fibrillation ablation, a 3D reconstruction of the pulmonary veins is required and that can be easily accomplished by this imaging modality.  You may be sent for this test if you have:  

• Intermediate to high-risk profiles for coronary artery disease, but who do not have typical symptoms (especially chest pain, shortness of breath, or fatigue during heavy physical activity.)
• Unusual symptoms for coronary artery disease (such as chest pain unrelated to physical exertion), but low to intermediate risk profiles for coronary artery disease.
• Unclear or inconclusive stress-test results.
• There is suspicion for congenital anomalous coronary arteries.
• Having ablation and pulmonary vein isolation for atrial fibrillation (AF) as 3D reconstruction of the left atrium and all pulmonary veins is generally required.

How does it work?

A Cardiac CTA comes from a special type of X-ray examination. Patients undergoing a Coronary CTA scan receive an iodine-containing contrast dye as an IV solution to ensure the best images possible. The same IV in the arm may be used to give a medication to slow or stabilize the patient’s heart rate for better imaging results. During the examination, which usually takes about 10 minutes, X-rays pass through the body and are picked up by special detectors in the scanner. Coronary CTA often is referred to as “multi-detector” or “multi-slice” CT scanning and the standard detector is a “64 slice.”  The information collected during the Coronary CTA examination is used to identify the coronary arteries and, if present, plaques in their walls with the creation of 3D images on a computer screen.  Additionally other structures can be visualized such as the sac around your heart (pericardium) as well as parts of the thoracic aorta.

How does a Cardiac CTA differ from a coronary angiogram?

A cardiac catheterization is an invasive test that requires a small catheter inserted directly into a leg or arm artery.  That catheter must then be passed up directly into the coronary arteries of your heart after which iodinated dye is directly injected into each artery multiple times each.  This is compared to a Cardiac or Coronary CTA that requires only an IV catheter inserted into a vein in one of your arms.  Although Cardiac CTA examinations are growing in use, coronary angiograms remain the “gold standard” for detecting coronary artery stenosis (a narrowing of an artery).  On the other hand, this new technology has consistently shown the ability to rule out significant narrowing of the major coronary arteries and can non-invasively detect “soft plaque” in their walls that has not yet hardened (and can not be seen by traditional cardiac catheterization, but that may lead to future problems without lifestyle changes or medical treatment.

Who may not be an ideal candidate to have a Coronary CTA?

While Coronary CTA has excellent negative predictive value (a normal test almost completely rules out significant blockages in the major arteries), it should not be ordered if there is an expectation that significant disease exists and an intervention may be required (angioplasty/stent or bypass surgery).  To date, Coronary CTA has not been proven as effective as the coronary angiogram in detecting disease in the smaller heart arteries or in previously stented vessels. Coronary CTA also is of limited use in patients with extensive areas of old calcified, plaque, as significant calcified can prevent adequate visualization of the vessel.  Patients most likely to have significant coronary calcification are often older patients or patients that have been on dialysis for some time. Patients who are extremely overweight or who have irregular heart rhythms also tend not to be suitable candidates for this test because imaging quality is compromised.  Other relative contraindications include dye allergy and renal dysfunction (kidney problems).

What is the procedure for getting a Coronary CTA examination?

When your cardiologist decides with you that a Coronary CTA is appropriate, one of our schedulers will help to schedule you at Fairfax Hospital.  Many times insurance companies require pre-certification and this step is conveniently taken care of by our office.  Additionally your cardiac history and basic laboratory studies are required to be sent over to the hospital at least the day before the Cardiac CTA is scheduled.

How to prepare:

• Avoid any caffeinated drinks on the day before or the day of your exam. Coffee, tea, energy drinks, or caffeinated sodas.
• Do not use Viagra or any similar medication on the day before or the day of the exam. It is not compatible with the medications you will receive during the procedure (ask your doctor if you have questions).
• On the day of your exam, do not eat for four hours prior to your scheduled appointment. You may drink water.
• Diabetic patients:  If on insulin: Take ½ dose of prescribed dose night before and morning of the test. If taking oral (by mouth) diabetic medications: No oral diabetic medications on the day of the procedure. 
• Tell the nurse, technologist and your doctor if you are:
• pregnant
• allergic to iodine and/or shellfish or any medications
• have a history of kidney problems

What to expect:

• You will change into a hospital gown.
• A nurse will insert an IV line into a vein in your arm to administer contrast (dye) during your procedure.
• You will lie on a special scanning table.
• The technologist will clean three small areas of your chest and place small, sticky electrode patches on these areas. Men may expect to have their chest partially shaved to help the electrodes stick. The electrodes are attached to an electrocardiograph (ECG) monitor, which follows your heart’s electrical activity during the test.
• You will lie on the scanner table, and you will be asked to raise your arms over your head for the duration of the exam.
• During the scan, you will feel the table move inside a donut-shaped scanner. You will receive a contrast agent through your IV to help produce the images. It is common to feel a warm sensation as the contrast circulates through your body.
• Once the technologist is sure that all the information is collected, the IV will be removed.
• The CT scan should take about 15 minutes.

After the procedure:

• You may return to all normal activities including eating.
• Your physician will receive the results of the test and discuss the results with you.