A coronary artery calcium (CAC) scan is a common, non-invasive imaging test that uses Computed Tomography (CT) to look inside the arteries of the heart. This procedure assesses the presence of calcified plaque, which is directly related to a person’s risk for heart disease. Understanding the process, from preparation to receiving the results, helps clarify what to expect from this important health screening. This article explains the test components, necessary preparation steps, and the actual time commitment involved in getting a coronary calcium scan.
What Does a Coronary Calcium Scan Measure?
The coronary calcium scan is a specialized CT scan designed to detect and quantify calcium deposits specifically within the walls of the coronary arteries. The presence of calcium in these arteries is a sign of atherosclerosis, commonly known as plaque buildup. This plaque is composed of fat, cholesterol, and calcium, and its accumulation can narrow the arteries and impede blood flow over time.
This non-invasive test does not require an injection of contrast dye, relying instead on the natural density of calcium to appear brightly on the CT images. The scan provides a quantitative measure of the total plaque burden, which helps estimate the extent of coronary artery disease.
The test does not directly measure whether an artery is significantly blocked, but rather the total amount of hardened plaque. Detecting this calcification helps identify heart disease at its earliest stages, often before symptoms appear. The resulting score is a strong predictor of future cardiac events and helps healthcare providers determine a person’s long-term cardiovascular risk.
Preparing for the Procedure
Before the scan, patients must take a few simple steps to ensure the best possible image quality for the CT machine. The primary goal of preparation is to keep the heart rate low and steady during the brief imaging acquisition. To achieve this, patients are typically instructed to avoid caffeine and smoking for a minimum of four hours before the appointment.
Caffeine, nicotine, and even strenuous exercise can temporarily elevate the heart rate, making it challenging for the scanner to capture clear, freeze-frame images of the heart. Patients should always follow the specific instructions provided by their imaging center, as some facilities may recommend avoiding these substances for up to 12 hours.
Patients should wear comfortable, metal-free clothing to the appointment and remove any jewelry, belts, or other metal objects that could interfere with the CT images. Upon arrival, a technician will place small, sticky electrode patches on the patient’s chest, which are connected to an electrocardiogram (EKG) machine. These electrodes monitor the heart’s electrical activity throughout the procedure. The EKG synchronization allows the CT scanner to time its image acquisition precisely with the heart’s movement, capturing the clearest possible pictures between heartbeats.
Scan Duration: The Difference Between Imaging Time and Appointment Time
It is important to understand the significant difference between the length of time the actual scan takes versus the entire visit duration. The total appointment time from check-in to exit is generally between 15 and 30 minutes. This period accounts for all the necessary steps required to prepare the patient and process them through the facility.
This longer window includes the administrative process of checking in, changing into a gown if necessary, and the time the technician spends explaining the procedure. The placement and setup of the EKG electrodes on the chest also contribute to this preparation time. Once prepared, the patient is positioned on the CT scanner table and given instructions for breath-holding.
The actual imaging acquisition time, the period when the CT scanner is actively taking pictures, is remarkably short. Active scanning typically lasts only a few seconds, often less than 15 to 30 seconds of total breath-holding time. The entire process of lying on the table and having the images taken is usually completed in under five to ten minutes.
The speed of the CT scanner is fundamental to the test’s success, as it must capture high-resolution images of a constantly moving organ. The brief duration of the actual scan minimizes the chance of motion blur and ensures the clarity needed for accurate scoring.
Understanding Your Agatston Score
The result of the coronary calcium scan is quantified using the Agatston Scoring system, which is a numerical value reflecting the total volume and density of the calcified plaque detected. This score is a powerful tool for risk stratification, helping determine a person’s likelihood of experiencing a heart attack or other cardiac event. The score can range from zero to over 1,000, and a higher number indicates a greater burden of disease.
A score of zero is the best possible result, indicating that no calcified plaque was detected in the coronary arteries. This score is associated with a very low risk of a heart attack over the next decade. Finding any calcium, even a small amount, means the process of atherosclerosis has begun.
Scores ranging from 1 to 100 suggest a mild degree of coronary artery disease, while a score between 101 and 400 indicates a moderate level of plaque. Patients with scores in the moderate range have a relatively high risk for a cardiac event within the next three to five years. A score exceeding 400 is considered severe, signifying an extensive amount of plaque and a significantly increased risk of major cardiac events.
The Agatston score is not a diagnosis in itself, but rather a guide that facilitates an informed discussion with a healthcare provider. The score helps determine whether a patient may benefit from aggressive risk management strategies, such as lifestyle changes, diet modification, or the initiation of cholesterol-lowering medications.