The Coronary Artery Calcium Score (CACS) is a measurement derived from a non-invasive computed tomography (CT) scan that quantifies the amount of calcified, or hardened, plaque within the heart’s arteries. This calcification is a sign of atherosclerosis, a disease where plaque builds up inside the arteries. The CACS, reported as an Agatston score, is a tool for predicting the long-term risk of future cardiac events, such as a heart attack, as it correlates with the total volume of atherosclerotic plaque. While a high score indicates an elevated risk profile, the score alone rarely dictates the need for an immediate intervention like a stent. The primary purpose of the CACS is to guide long-term risk management and determine the necessity of more aggressive preventive therapy.
Interpreting Coronary Artery Calcium Scores
The Agatston score is the most common way to report CACS. It is calculated based on the area and density of detected calcium deposits, serving as a quantifiable measure of the overall burden of coronary artery disease. The score is used to categorize a person’s risk into distinct levels to guide prevention strategies.
A CACS of zero indicates no calcified plaque was detected, associated with an extremely low risk of a cardiac event over the next five to ten years. This “warranty period” suggests that aggressive medical therapy is usually not required, unless other risk factors are high. A score between 1 and 100 signifies a mild presence of coronary artery disease, suggesting a low to moderate risk, and often prompts intensified lifestyle modifications.
The intermediate risk category is defined by a CACS ranging from 101 to 400, or a score above the 75th percentile for the patient’s age and sex. This range demonstrates a moderate plaque burden and represents a need for therapeutic intervention to stabilize the existing disease. Scores greater than 400 are categorized as high risk, indicating extensive atherosclerotic disease and a risk of a cardiac event similar to that of a patient who has already had a heart attack. A CACS over 1000 places an individual in the very high-risk category, often associated with a ten-year event rate exceeding 25%.
Management Strategies Based on CACS Risk Levels
The detection of a positive CACS typically initiates a shift toward aggressive primary prevention strategies, rather than an immediate invasive procedure. For scores in the mild to moderate range (1–400), the initial approach involves intensive risk factor modification, including optimizing diet, increasing physical activity, and achieving a healthy body weight.
Pharmacological intervention is a cornerstone of managing elevated CACS, particularly for scores above 100. Statins are widely recommended to reduce low-density lipoprotein (LDL) cholesterol levels, often targeting a goal below 70 mg/dL for high-risk individuals. The aim of this aggressive medical therapy is to stabilize the existing plaque and prevent its rupture, the most common cause of a heart attack.
Management also involves rigorous control of other cardiovascular risk factors, such as high blood pressure and diabetes. Antiplatelet therapy, like low-dose aspirin, may be considered in certain patients with a CACS above 100, especially if they are not at high risk for bleeding. The CACS acts as a risk differentiator, guiding clinicians on the necessary intensity of treatment to prevent a future event.
The Criteria for Stent Placement
The core distinction determining the need for a stent is the difference between the volume of calcified plaque, which the CACS measures, and the functional limitation of blood flow. A stent, or percutaneous coronary intervention (PCI), is reserved for arteries that are critically narrowed, a condition known as hemodynamically significant stenosis. This procedure physically restores adequate blood flow to the heart muscle.
A high CACS does not directly translate to a flow-limiting blockage because the calcified plaque may be distributed along the artery walls without significantly obstructing the central channel. The decision to place a stent is based on functional evidence that the blockage is restricting blood flow, typically defined as a narrowing of 70% or more. This evidence is gathered through follow-up diagnostic testing.
A CACS in the high-risk range may prompt functional tests, such as a stress test, to check for signs of ischemia, or reduced blood flow, to the heart muscle. If these non-invasive tests are abnormal, a coronary angiogram may be required to visualize the artery blockages directly. The angiogram is the definitive test, and the decision to proceed with a stent is based on the severity of the blockage found, especially if the patient is experiencing symptoms like unstable angina.