What is Coronary CT Angiography?
Computed tomography is an excellent tool in the detection of heart disease. Coronary CT Angiography is a new technology that allows physicians clear visualization of blood flow to the heart muscle, the pumping function of the heart, and any calcium deposits in the vessels and/or any narrowing of the heart vessels that can cause a heart attack or stroke. Coronary CT Angiography is a non-invasive alternative to traditional angiography that offers more detailed images of heart function, resulting in faster, more accurate diagnosis. For some patients with chest pain, Coronary CT Angiography can rule out the need for cardiac catherization.
Who should consider a coronary CTA?
The single most important step for patients trying to determine whether they should consider a coronary CTA is consultation with their primary physician. Overall, coronary CTA examinations have tended to help determine a lack of significant narrowing and calcium deposits in the coronary arteries, as well as the presence of fatty deposits. Particularly, this has been found to exclude coronary artery disease.
For these types of patients, coronary CTA can provide important insights to their primary physician into the extent and nature of plaque formation with or without any narrowing of the coronary arteries. Coronary CTA also can noninvasively exclude narrowing of the arteries as the cause of chest discomfort and detect other possible causes of symptoms. Initial consultation with a primary physician is key for patients seeking to determine the appropriateness of coronary CTA. However, coronary CTA does have its limitations. For example, it is not able to image people with irregular heart rhythms. Also, very obese patients or those with heavily calcified arteries may not benefit from this exam.
- Intermediate risk profiles for coronary artery disease with suspicious cardiac symptoms
- Unusual symptoms for coronary artery disease (such as chest pain unrelated to physical exertion) with low to intermediate risk profiles for coronary artery disease
- Evaluation of chest pain in patients with uncommon symptoms or unclear stress test results
- Those with suspected congenital abnormalities of coronary arteries
- Detection of sub-clinical heart disease as the basis for primary prevention
- Pre-surgical assessment of coronary arteries
- Evaluation of coronary artery abnormalities
- Checking the patency of previously placed bypass grafts
How does the test work?
Using an intravenous (IV) line, iodine containing contrast dye is injected into your vein. The CT scanner, which is monitoring your pulse (heart) rate, measures when the contrast will reach the heart vessels. When the contrast is in the heart vessels, the CT scanner takes hundreds of images of your heart and then puts those back together to form a picture of your heart. Unlike a normal snapshot, this picture can be broken down to show just the arteries, the muscles or the veins.
Before the test
Avoid any caffeinated drinks for 24 hours prior to your test, including coffee, tea, energy drinks or caffeinated sodas. Avoid energy or diet pills for 24 hours prior to test. Do not eat for 4 hours prior to the test. Please bring a list of your current medications and dosages. Continue taking medications as prescribed by your physician, unless otherwise instructed. During your visit Throughout the procedure a nurse will monitor your blood pressure, heart rate, and heart rhythm and oxygen levels. The nurse will insert an IV in your right arm.
During the test, this IV will be used to give you a contrast dye, which is used to enhance the visibility of certain tissues. During the injection of the contrast dye, you may feel a warm, flushed sensation. This feeling is normal for any contrast injection. If your heart rate is above 60 beats per minute, you will be given a beta-blocker called metoprolol to slow the rate. A slower heart rate allows us to see your heart better and obtain clearer pictures with the CT scanner. You may also be given a medication called nitroglycerin (0.4 mg) that will be sprayed under your tongue. This medicine dilates the vessels around your heart to allow better visualization of those vessels. Once your heart rate is 60 beats or slower, the technologist will give you breathing instructions and the technologist will begin taking pictures. You may be asked to hold your breath during the scanning. Any motion, whether breathing or body movements, can lead to artifacts on the images.
The examination table will move into and out of the scanner opening, but it is not enclosed, and only a small part of your body will be inside at any one time. You will lie on a scan table that slides slowly into a large circular opening in the scanning machine that looks like the hole in a doughnut. The CT staff will be in the control area, adjacent to the CT room. You will be in sight of staff through a window. Speakers inside the scanner will allow staff to talk with you and hear you. The technologist will be watching you at all times and be in constant communication. Once the test is completed, you will be observed for a few minutes and then discharged to go home.
After the coronary CTA, you should drink a lot of water for the next 24 hours to help flush the contrast out of your system.
How do I obtain my results?
A radiologist and a cardiologist will review and interpret the results of your test and share them with your referring physician. Your doctor will then discuss the results with you.