The Coronary Artery Calcium (CAC) score test is a non-invasive procedure that uses a computed tomography (CT) scan to assess heart attack risk. This specialized scan measures the amount of calcified plaque in the coronary arteries, which is a direct indicator of coronary artery disease (CAD). Plaque buildup, or atherosclerosis, causes the hardening and narrowing of arteries, and the resulting calcium deposits are easily detected by the CT imaging technology. The test provides a quantitative score, the Agatston score, which helps physicians determine a patient’s future cardiovascular risk and guide preventative treatment plans.
Fasting Requirements and Dietary Restrictions
A full fast is not required before a standard CAC score test, unlike blood tests for cholesterol or glucose. The CT scan focuses on calcium deposits, and the presence of food in the digestive system does not interfere with the imaging process. However, there are very specific and mandatory restrictions related to substances that affect heart rate.
The heart must be beating slowly and steadily during the scan, which is crucial for obtaining clear images. Therefore, you must strictly avoid all sources of caffeine, including coffee, tea, energy drinks, soda, and chocolate, for a period of four to twelve hours before the examination. Nicotine, from smoking or other tobacco products, acts as a stimulant and must also be avoided for several hours prior to the test for the same reason. High heart rates cause motion blur in the CT images, which can lead to an inaccurate measurement of the calcium deposits.
Non-Dietary Pre-Test Preparation
Beyond dietary restrictions, several simple physical and logistical preparations will ensure a smooth and successful scan. Patients should wear comfortable, loose-fitting clothes, preferably a two-piece outfit. This makes it easier to position for the scan and to attach the necessary monitoring equipment.
It is important to leave all jewelry and metal objects at home, as metal interferes with the CT imaging process and can create artifacts in the pictures. This includes necklaces, earrings, and any clothing items with metal snaps, zippers, or underwires. If you are currently taking prescription medications, continue them as scheduled unless your referring physician or the imaging center explicitly instructs you otherwise. Arriving approximately 15 to 30 minutes before the scheduled time allows for necessary paperwork, insurance verification, and a final review of the preparation instructions.
What to Expect During the Scan
Upon arrival, you will change into a hospital gown and remove any metal objects or jewelry. The technologist will then have you lie flat on your back on a cushioned, movable table that slides into the CT scanner.
Small, sticky electrode patches will be placed on your chest, which connect to an electrocardiograph (EKG) monitor. The EKG continuously tracks your heart’s electrical activity, a process known as cardiac “gating.” This gating mechanism synchronizes the CT image acquisition to specific, quiet points in your heart’s cycle to freeze the motion of the beating heart and produce sharp, clear pictures. The technologist will operate the machine from an adjacent room but can see, hear, and communicate with you through an intercom.
The actual scan is very fast, often taking less than 15 minutes from start to finish. The CT imaging phase itself is typically over in just a few seconds. You will be asked to hold your breath briefly, usually for about 10 to 20 seconds, to prevent any breathing motion from blurring the images. The procedure is non-invasive and painless, and you will be able to resume your normal activities immediately afterward.
Interpreting the Calcium Score Results
The Agatston score quantifies the total area and density of calcified plaque found in your coronary arteries. This score is a powerful predictor of future cardiovascular events and is used to stratify your risk.
Score Ranges
- A score of zero means no calcified plaque was detected, which suggests a very low risk of a heart attack over the next several years.
- A score between 1 and 99 indicates a mild amount of plaque, suggesting an increased but still low risk of coronary artery disease.
- Scores in the 100 to 399 range signal a moderate amount of plaque and are associated with a relatively elevated risk of a heart attack in the coming three to five years.
- A score of 400 or higher signifies an extensive burden of calcified plaque, indicating severe coronary artery disease and a significantly high risk for future heart events.
Physicians use the Agatston score, often in combination with other risk factors, to determine the most appropriate preventative treatment. A higher score may prompt the initiation of medications like statins or aspirin and reinforce the urgency of aggressive lifestyle modifications. The results help guide decisions about management strategies to effectively lower your long-term cardiovascular risk.