The Coronary Artery Calcium (CAC) score test is a non-invasive computed tomography (CT) scan designed to detect and measure calcified plaque within the walls of the heart’s arteries. This calcified material signals the presence and extent of atherosclerosis, often called coronary artery disease (CAD), which is the underlying cause of many heart attacks and strokes. The test yields a numerical result, the calcium score, which serves as a powerful predictor of future cardiovascular events.
The procedure is typically recommended for asymptomatic individuals, generally those between 40 and 70 years old, who are at an intermediate risk for heart disease. For people whose risk is uncertain, the CAC score provides a more precise assessment, helping doctors make informed decisions about preventative treatment. This score moves beyond simple risk factor assessments by directly measuring the amount of disease present in the arteries.
Specific Preparation Guidelines
Fasting before a calcium score test is generally not strictly required, but a brief fast is often recommended for the highest quality images. Some facilities advise avoiding all food for about four hours before the scan, though drinking water is usually permitted. This restriction reduces the chance of stomach contents interfering with the imaging field.
More important than food fasting is abstaining from substances that elevate your heart rate. Patients must avoid all sources of caffeine, nicotine, and energy drinks for at least four to twelve hours before the scheduled appointment. A high heart rate causes motion blur on the CT images, making it difficult to accurately measure the tiny calcium specks in the coronary arteries. Strenuous exercise should also be avoided.
You should wear comfortable, two-piece clothing. Any metal on your body, including jewelry, hairpins, zippers, and underwire bras, must be removed before the scan, as metal interferes with the CT imaging process. Continue taking all prescribed medications as usual unless your healthcare provider gives you specific instructions otherwise.
What to Expect During the Test
The calcium score test is a quick, non-invasive procedure performed in a CT scanner, a large machine with a doughnut-shaped opening. Once positioned on the table, a technician attaches several small, sticky electrode patches to your chest. These electrodes connect to an electrocardiogram (EKG) machine, which monitors your heart’s electrical activity.
The EKG synchronizes the CT scan’s image acquisition with your heartbeat, a technique called “gating.” Gating ensures the images are captured when the heart is still between beats. The table slides you into the scanner, and the technician communicates from an adjacent control room. You will not feel anything during the scanning process.
For the brief moments images are being taken, the technician asks you to hold your breath for 10 to 20 seconds. This momentary breath-holding prevents blurring caused by lung or chest movement. The entire procedure, from preparation to completion, usually takes only about 10 to 15 minutes.
Interpreting Your Calcium Score
The final result of the test is reported as the Agatston score, a number calculated based on the total area and density of the calcified plaque found in your coronary arteries. The magnitude of this number directly correlates with your risk for a future cardiovascular event. A score of zero is the best possible result, indicating no calcified plaque was detected and associating with a very low risk of a heart attack over the next several years.
Agatston Score Ranges
Scores between 1 and 100 suggest a mild amount of plaque and a low-to-moderate risk, potentially warranting lifestyle modifications. A score ranging from 101 to 400 indicates a moderate plaque burden and a moderate-to-high risk, which is a strong indication of existing heart disease. Scores above 400 represent extensive plaque and a high probability that at least one coronary artery is significantly narrowed.
Regardless of the result, your doctor will discuss the score in the context of your overall health profile, including your age, sex, and other risk factors. Higher scores often lead to a recommendation for more aggressive preventative strategies, such as statin therapy or further diagnostic testing. The score is a valuable tool that helps guide personalized decisions about managing your long-term heart health.