The Coronary Artery Calcium (CAC) score is a non-invasive tool that assesses a person’s risk for future cardiovascular events. Derived from a computed tomography (CT) scan, the score quantifies the amount of calcified plaque in the coronary arteries, measuring established atherosclerosis. The Multi-Ethnic Study of Atherosclerosis (MESA) established the score’s predictive power. This measurement is an independent predictor of heart attack, stroke, and other adverse cardiac outcomes.
Understanding the Coronary Artery Calcium Test
The CAC test uses a specialized, non-contrast computed tomography (CT) scan to capture images of the heart’s arteries. This quick procedure measures the density and extent of calcium deposits within the coronary artery walls. These deposits represent stable, accumulated plaque, indicating the presence of atherosclerosis, the disease process that causes most heart attacks.
The resulting number is the Agatston score, the standard method for quantifying coronary calcium. This score is calculated by factoring both the area and density of the calcified lesions; a larger and denser deposit contributes more to the final number. This measurement of established plaque burden provides a personalized assessment of cardiovascular risk.
Interpreting Your CAC Score
The concept of a “good” CAC score is straightforward: the lower the number, the lower the risk of a future cardiac event. The best result is a score of 0, indicating no detectable calcified plaque. Individuals with a CAC score of 0 have a very low estimated 10-year risk of a heart attack or stroke, typically less than one percent, associated with an excellent prognosis.
A score between 1 and 100 signifies a small amount of calcified plaque, suggesting a low to moderate risk of an event (generally less than 10 percent over ten years). This range suggests early or minimal coronary artery disease. Scores between 101 and 400 indicate moderate plaque buildup, classifying the risk as intermediate to moderately high, with a 10-year event risk of 10 to 20 percent. A score greater than 400 represents extensive calcification and a high risk of a future event, corresponding to a 10-year risk exceeding 20 percent.
The MESA study data adds context by translating the score into a percentile ranking. This percentile compares an individual’s score to others of the same age, sex, and ethnicity, which is important because calcium accumulation naturally increases with age. For example, a score of 150 may be average for an older man but above the 75th percentile for a younger woman, suggesting a higher relative risk for her age group.
Clinical Implications and Next Steps
The CAC score guides the personalized strategy for preventing heart disease. For individuals with a score of 0, the focus is generally on maintaining a healthy lifestyle. Preventive medications like statins or aspirin are often withheld due to the low risk, allowing patients and doctors to avoid medications that carry potential side effects.
A positive score requires a more aggressive approach to risk factor management, with intensity correlating directly with the score’s magnitude. For a score of 100 or greater, evidence suggests a significant benefit from initiating statin therapy to lower cholesterol, as this group is at a higher risk of future events. A score of 100 or more can also help identify patients who may benefit from low-dose aspirin therapy for primary prevention, as the benefit of preventing a heart attack outweighs the risk of bleeding.
Lifestyle Modifications
Regardless of the score, comprehensive lifestyle modification remains a foundation of heart health prevention. These actions stabilize existing plaque and help slow the progression of atherosclerosis. Key modifications include:
- Adopting a heart-healthy diet.
- Engaging in regular physical activity.
- Maintaining a healthy body weight.
- Completely stopping all tobacco use.
Consulting with a physician or cardiologist is necessary to integrate the CAC score with other traditional risk factors, such as blood pressure and cholesterol levels. The CAC score is not a standalone diagnosis but one piece of information that helps tailor a personalized medical strategy. The results help a doctor decide whether to start a medication, adjust a dosage, or focus on lifestyle measures, refining the overall preventive strategy.