The Coronary Artery Calcium (CAC) scoring test is a non-invasive medical imaging procedure that uses a specialized Computed Tomography (CT) scan to detect and quantify calcified deposits (plaque buildup) in the arteries supplying the heart. These deposits are a hallmark of atherosclerosis. This process results in a numerical score that helps physicians determine an individual’s risk of having a heart attack or developing serious heart disease. The test is painless and designed to be quick, making the total time commitment a common question for people considering the screening. This article addresses the logistics of the test, from preparation to the final result interpretation.
What the Calcium Score Measures
The primary function of the CAC test is to measure the amount of calcified plaque present within the walls of the coronary arteries. Coronary artery disease begins with the slow accumulation of fatty substances, cholesterol, and cellular waste, collectively known as plaque, beneath the inner lining of the arteries. Over time, these soft, fatty deposits begin to incorporate calcium, causing them to harden and making them detectable by the CT scanner.
The presence of calcium is a direct indicator of underlying atherosclerosis, which is the narrowing and hardening of the arteries. Because the calcium deposits are a late-stage component of plaque formation, the amount of calcium measured serves as a proxy for the total burden of atherosclerotic plaque an individual carries. The test does not directly visualize soft, non-calcified plaque, but it does provide a powerful measure of disease progression.
The resulting measurement, called the Agatston score, is calculated by considering both the area and the density of the detected calcium deposits. This scoring method provides a highly individualized assessment that goes beyond traditional risk factors like cholesterol levels or blood pressure. It is particularly useful for risk stratification in asymptomatic individuals who may have intermediate risk based on conventional prediction models. A patient’s calcium score helps healthcare providers decide whether a person should begin aggressive preventive measures, such as statin therapy or aspirin.
The Procedure: Preparation, Duration, and Steps
The entire appointment for a Coronary Artery Calcium scan typically takes between 30 and 45 minutes at the facility from check-in to discharge. The most time-consuming part of the process involves the preparatory steps and post-scan quality checks, not the actual imaging itself.
Before arriving, patients are typically advised to avoid consuming caffeine, smoking, or engaging in strenuous exercise for at least four hours prior to the scan. These activities can increase the heart rate, which would introduce motion blur into the images and make the scan less accurate. Patients should also wear comfortable, loose-fitting clothing and be prepared to remove metal objects, such as jewelry, eyeglasses, or bras with underwires, as metal interferes with the CT imaging.
Upon arrival, the initial steps involve paperwork, changing into a gown, and preparing for the scan. Once in the CT room, a technologist will place small, sticky electrodes on the patient’s chest, which are connected to an electrocardiograph (EKG) machine. This EKG synchronization, or gating, monitors the heart’s electrical activity and allows the CT scanner to capture images only during the brief moments when the heart is at rest. This technique minimizes motion artifacts and ensures a clear, high-resolution picture of the coronary arteries.
The patient lies flat on the CT table, which slides into the donut-shaped scanner. The actual image acquisition is extremely fast, often taking less than one minute of scanning time. During this short period, the patient will be asked to hold their breath for 10 to 20 seconds to ensure the heart remains perfectly still for the image capture. The total time spent on the scanning table, including the placement of the EKG leads and the brief scan, is typically 10 to 15 minutes.
Understanding Your Score and Next Steps
The final result of the CAC test is presented as a numerical Agatston score, which is strongly correlated with a person’s risk for a cardiovascular event. A score of zero is the most favorable result, indicating no detectable calcified plaque and suggesting a very low probability of a heart attack over the next decade. This finding can often lead to a de-escalation of preventive treatment.
Scores between 1 and 100 suggest the presence of minimal to mild calcification, which is typically associated with a mildly increased risk. In this range, a physician will likely recommend intensive lifestyle modifications and may consider initiating low-dose preventive medications. A score between 101 and 400 signifies a moderate amount of plaque and a moderately increased risk of a cardiac event. At this level, treatment with statin medication is often recommended to slow the progression of atherosclerosis.
A score greater than 400 indicates a severe plaque burden and places the individual in a high-risk category, sometimes comparable to someone who has already experienced a heart attack. This result requires aggressive management of all modifiable risk factors, often involving high-intensity statin therapy and potentially a referral for further diagnostic testing, such as a stress test or a CT angiogram. Ultimately, the score provides a clear, personalized snapshot of heart health that allows a physician to tailor a precise and proactive treatment plan.