Cardiac (Coronary) CT Angiography

What is a Cardiac CT Angiography (CTA)?

One of the most common tests used to evaluate the heart in patients with chest pain is a "coronary angiogram" or "cardiac catheterization." Performed by a cardiologist who injects dye or intravenous contrast into the vessels and chambers of the heart, this test is invasive (requiring the placement of catheters and wires in the coronary arteries, typically inserted through the groin under local anesthesia) and requires patient recovery time in the hospital upon completion of the procedure. Cardiac CTA, on the other hand, is a non-invasive, special type of X-ray procedure performed by a radiologist using a CT scanner. Cardiac CTA helps to determine whether fatty deposits or calcium deposits, also called plaques, have built up in the walls of the coronary arteries that supply blood to the heart muscle itself. If such plaque builds up untreated, it may cause a narrowing and decrease the blood flow to the heart muscle that could result in chest pain or even a heart attack. A cardiac CTA not only evaluates the coronary arteries but also the heart muscle, heart valves, contraction function of the heart (ejection fraction), lung vessels, protective sac around the heart (pericardium), other structures in the center of the chest, and the portion of your lungs and chest wall included in the scan. Intravenous iodine-containing contrast is administered during the test to determine whether it flows freely through the coronary arteries. The test can only be performed if the patient does not have a CONTRAST ALLERGY or KIDNEY DISEASE. Kidney disease is screened for prior to the CTA test with a simple blood test. Radiologists and cardiologists at Lahey Clinic work together as a team interpreting cardiac CTA images for optimum patient care.

Anterior 3D view of the heart showing the right and LAD - left anterior descending coronary arteries. Oblique 3D view of the heart showing the right, LAD - left anterior descending, and circumflex coronary arteries. Posterior 3D view of the heart showing the circumflex coronary artery.

How to Prepare for Cardiac CTA

• Avoid any caffeinated drinks (coffee, tea, energy drinks, or caffeinated sodas) on the day before and the day of your exam.
• As mentioned previously, you will be required to have a simple blood test to evaluate your kidney function prior to receiving any intravenous contrast agent.
• Avoid energy or diet pills on the day before and the day of your exam (ask your doctor if you have questions).
• Do not use Viagra or any similar medication on the day before and the day of your exam. Such drugs are not compatible with medications you will receive during the procedure (ask your doctor if you have questions).
• On the day of your exam, do not eat solid food for four hours prior to your scheduled appointment. However, you may drink plenty of water.
• If you are diabetic: Tell the CT technologist if you take glucophage, glucovance, metformin or metaglip. You will need to stop taking these medications for 48 hours after your scan and have your blood redrawn before you resume taking your medication. If you think your blood sugar is low, tell the technologist immediately. If you take insulin, you need to adjust your normal dose on the day of the exam according to your doctor's instructions since you will not be eating anything in the morning and therefore will be at risk for low blood sugar.
• Tell your technologist and your doctor if you are:
  • pregnant or
  • allergic to iodine or any medications.

What to Expect

You will receive a reminder call a few days prior to your examination to confirm your appointment date and time and to be sure that all your questions are answered. At that time we may also ask you some additional questions regarding your medical history if we do not have sufficient information in our records.

On the Day of the Examination:

• You will be asked to change into a hospital gown.
• A nurse will clean three small areas on your chest and place small, sticky electrode patches on these areas. (Men may expect to have their chests partially shaved to help the electrodes adhere to the skin.) The electrodes are attached to an electrocardiographic (ECG) monitor, which charts your heart's electrical activity during the test. Your heart rate will be monitored before, during and after the study.
• A nurse or technologist will insert an IV line into a vein in your arm to administer intravenous contrast (dye) during your procedure. Our staff will monitor your heart rate and blood pressure prior to the test. If your heart rate is too high for the test (too fast to get good motion-free images), the nurse or a doctor may inject intravenous metoprolol (a beta blocker medication) to lower your heart rate to the desired level during the study.
• Once you have been transferred to the scanner table, you will be asked to raise your arms over your head for the duration of the exam. During the scan, try to remain calm by relaxing and focusing on the breathing instructions given. There may be quiet times when the technologists are programming the scanner. This is normal procedure and nothing to worry about.
• You will feel the table move you into a donut-shaped scanner with a large opening for your body to fit through. Initially, your heart will be scanned to obtain what is called a coronary calcium score that evaluates the amount of calcific plaques on your coronary arteries. If this number is too high, intravenous contrast may not be injected.
• Just prior to the exam, you will receive one or two puffs of nitroglycerine (under your tongue) which helps enlarge your coronary arteries to make them more visible.
• You will also receive an intravenous contrast agent through your IV to help produce optimal images. It is common and normal to feel a warm sensation as the contrast circulates through your body. Some patients may also sense a metallic taste in their mouth.
• Once the technologist is sure that all the necessary information has been collected, you will be transferred from the scanner table to the monitoring area. Depending on whether you received any medication to lower you heart rate, you may be observed for another half hour to make sure you are doing well. If all is well, the IV line will be removed and you will be sent home.

After the Study

Be sure to eat well and drink plenty of fluids. Although aftereffects of the examination are rare, if you experience any chest pain, dizziness, shortness of breath or other unexpected symptoms, immediately call the closest ER.

Frequently asked Questions

Why do I need contrast?

Contrast is injected via the veins and shows up bright inside the vessels on the CT images. This helps the radiologist identify the coronary arteries and characterize atherosclerotic disease (also called plaque or "hardening of the arteries"). It is commonly used in many different types of CT tests and you may already have had a contrast injection in the past.

Will I be allergic to contrast?

A small percentage of patients may have an allergic reaction to iodinated contrast. Patients should always alert their doctors prior to the examination if they have had an allergic reaction to contrast in the past. If they have had a prior allergic reaction, they may be given medication to prevent a repeat reaction before the examination. If a patient has an allergic reaction during the exam, our radiologists are prepared to treat the reaction.

How long will my scan take?

The average length of time spent in the scanner room is around fifteen to thirty minutes. Of course, the test will not be initiated until your heart rate is in the desired range. The entire duration of your visit including preparation once you arrive at Lahey Clinic until the scan is completed may take up to 2 hours.

Conclusion

The most effective treatment for heart disease is prevention. The earlier the warning signs of heart disease can be detected, the sooner you can begin reducing your risk. But for many people, there are no warning signs. Coronary CTA can detect coronary artery disease even before the onset of symptoms.

If you have any further questions regarding the procedure and what to expect, you can contact the Radiology CT department at 781.744.8160.