About the CT Exam

Coronary Artery CTA Examinations:How to Prepare & What to Expect

What should someone expect when undergoing a coronary CTA examination? The process begins when the scan is scheduled. Patients are asked a series of questions designed to determine their symptoms and any history of prior cardiac treatment or interventions. This allows the scan to be properly tailored to the needs of the patient and referring physician. Additionally, patients are screened for use of certain medications, such as erectile dysfunction medications (see below).

There is some minor preparation involved before the scan. Patients usually arrive at the imaging center about 30 minutes before the scheduled appointment. Vital signs are assessed by a cardiac-trained nurse, and the indications for the scan are reviewed to be certain that the patient has the potential to benefit from the information the scan may provide. In particular, the patient's heart rate is assessed. The image quality, and thus the diagnostic capabilities of coronary artery CTA are closely related to the patient's heart rate. In general, a heart rate of 65 beats per minute or slower is desirable for optimal image quality. If the patient's heart rate is higher than this, oral or intravenous medications known as beta blockers are administered to slow the heart rate to the desired level. There are a few contraindications to these medications, such as known hypersensitivity to this class of drug, heart block, asthma and obstructive lung disease, and heart failure. These are screened for in the initial interview. If any of these contraindications are present, beta blockers are not administered. Often a patient's resting heart rate will be assessed before the day of the scan, and if beta blockers are required, oral medications may be prescribed and taken the morning of the scan prior to arrival at the imaging center.

Patients should not eat or drink at least 4 hours prior to the scan. In particular, patients should not have any caffeine for 6-8 hours prior to the scan because caffeine raises the heart rate. In general, laboratory studies evaluating kidney function are helpful for excluding kidney disease and are obtained prior to the day of the scan. This is important because the intravenous contrast used with CT examinations has the potential to exacerbate pre-existing disorders of kidney function. Pregnant patients should inform their doctors of the pregnancy and should also inform the CT technologists of the pregnancy prior to the scan, or even the possibility of pregnancy, because the x-ray radiation used for coronary artery CTA may be harmful to the developing fetus.

Prior to the scan, ECG patches are placed on the chest to record the ECG during the scan. An intravenous canula is placed in the arm for the contrast injection. Just prior to the scan, a tablet or spray of nitroglycerin is given under the tongue because nitroglycerin dilates the coronary arteries and provides better image quality. A few contraindications to the administration of nitroglycerin exist, in particular the use of erectile dysfunction medications - it is important to inform the nurse if you are taking such medications. The scan may still be performed, but nitroglycerin will not be administered.

At Scottsdale Medical Imaging, a noncontrast coronary artery calcification scan is performed prior to coronary artery CTA. If the calcium score is very high, often the radiologist will discuss the issue with the referring physician prior to proceeding to CTA because very high calcium scores are often associated with more difficult to interpret CTA examinations. If the information gained by the CTA portion of the study will not alter treatment plans after a high calcium score is found, then the CTA will not be performed because the potential risk of exposure to intravenous contrast and radiation, no matter how small, will not provide any management-altering information.

The coronary artery CTA examination itself begins with the injection of the intravenous contrast material. Often this injection causes a warm sensation, but this is temporary. The patient is asked to take a deep breath in and hold it while the scan is occurring - this lasts for 10 seconds or less. After the scan is completed, the patient may leave the imaging center immediately if they have not received intravenous beta blockers. If intravenous beta blockers were used, the patient is observed for 30 minutes after the scan to be certain no reaction has occurred, after which the patient may leave. If the patient wishes, they may review their images and discuss the findings with the radiologist after the completion of the scan. The radiologist will interpret the images and generate a report detailing the findings the same day as the scan, and this report is sent to the patient's referring physician.