The Coronary Artery Calcium (CAC) scan is a non-invasive computed tomography (CT) procedure that directly measures calcified plaque buildup in the heart’s arteries, quantifying the total burden of coronary atherosclerosis. This quick test, performed without intravenous contrast, generates an Agatston score, which is a powerful, independent predictor of future heart attacks and strokes. The presence of calcium indicates established disease, even in asymptomatic individuals. The CAC score enhances the accuracy of risk assessment beyond traditional factors like cholesterol or blood pressure, guiding preventative health decisions.
Who Should Get the Initial Coronary Artery Calcium Scan?
The CAC scan is primarily recommended for asymptomatic adults who are at an uncertain or intermediate risk for atherosclerotic cardiovascular disease (ASCVD). This population generally includes men aged 40 to 75 and women aged 45 to 75 who do not yet have a history of heart disease. The test is most informative for those whose estimated 10-year ASCVD risk falls into the borderline (5% to 7.5%) or intermediate (7.5% to 20%) categories. The CAC score helps reclassify their risk, refining the need for preventive medications.
Specific risk enhancers, such as a strong family history of premature heart disease, diabetes, or severe cholesterol elevations, may warrant earlier testing. For example, men with diabetes might be considered for a first scan around age 37, and women around age 50. Conversely, the test is generally not recommended for individuals already diagnosed with coronary artery disease, those with severe symptoms, or those at very low risk. In these cases, the results would not change the established management plan.
Interpreting the Calcium Score Results
The Agatston score ranges from zero to over 1,000, with higher numbers correlating to a greater amount of calcified plaque and a higher long-term risk of a cardiac event. A score of zero indicates no detectable calcified plaque, conferring an excellent prognosis with a very low risk of a heart attack over the next five to ten years. This score often allows for the safe deferral of statin therapy, even in patients with other risk factors.
Scores between 1 and 100 represent mild plaque burden and a low-to-moderate risk of a future event. This range confirms the presence of atherosclerosis and suggests that a focused approach to lifestyle changes is necessary. Scores in the 101 to 400 range indicate moderate plaque burden and a significant risk, warranting a more aggressive clinical strategy.
A score over 400 signifies severe plaque accumulation and places the individual in a high-risk category, often equivalent to a person already diagnosed with heart disease. In addition to the absolute score, the percentile rank—comparing the patient’s score to others of the same age and gender—provides a secondary measure of risk. A score above the 75th percentile for one’s age and sex is considered a higher risk, even if the absolute score is below 400.
Guidelines for Repeat Testing Frequency
The decision to repeat a CAC scan is highly individualized and is determined almost entirely by the initial result. Current guidelines emphasize that repeat testing is most beneficial for those with a low initial score to monitor for progression. The interval for re-testing should balance the need for updated risk information against the small amount of radiation exposure involved.
For an initial score of zero, repeat scanning is generally not recommended for at least five to ten years, as the absence of calcium provides a long “warranty period” of low risk. However, if new, significant risk factors like diabetes or uncontrolled hypertension develop, an earlier re-scan may be considered after about five years. The risk of an event remains very low for individuals with a persistent zero score.
For scores in the low-to-moderate range of 1 to 400, repeat scanning is often considered three to five years later to assess the rate of plaque growth. A rapid increase in the score suggests aggressive disease progression and may prompt an escalation of preventive treatment. For those with scores over 400, repeat testing is usually unnecessary because the patient is already classified as high risk. The focus shifts entirely to intensive risk factor control rather than monitoring plaque growth with additional imaging.
Applying the Results to Treatment and Lifestyle
The CAC score is a powerful tool for shared decision-making, directly influencing the intensity of medical and lifestyle interventions. A score of 100 or greater often acts as a tiebreaker, leading to the initiation of moderate-to-high-intensity statin therapy, even if the patient’s cholesterol numbers were previously considered borderline. The presence of any calcium, even a score of 1, may motivate a physician to start a statin, especially in older patients.
A high score can also guide the use of low-dose aspirin for primary prevention, particularly for those with a score over 100. The result provides strong, personalized evidence that often increases a patient’s adherence to both medication and necessary lifestyle changes, such as improved diet and smoking cessation. In cases of scores exceeding 400, the physician may recommend further diagnostic testing, such as a stress test, to check for silent blockages that might require more immediate intervention.