The Coronary Artery Calcium (CAC) score is a tool used by healthcare providers to assess a person’s risk for a future cardiovascular event. This score provides a direct, quantitative measure of the amount of calcified plaque in the coronary arteries. By identifying the presence and extent of this hardened plaque, the CAC score offers an independent prediction of heart attack or stroke risk that goes beyond traditional risk factors.
What the Coronary Artery Calcium Test Measures
The CAC test is a non-invasive procedure that uses a specialized computed tomography (CT) scan of the heart. This scan, often called a heart scan, captures multiple X-ray images that are then processed by a computer to look specifically for calcium deposits in the coronary arteries. The presence of calcium in these arteries is a direct indicator of atherosclerosis, which is the long-term buildup of fatty plaque.
The calcium detected is a stable, hardened component of the atherosclerotic plaque, signifying that the disease process has been underway for several years. Once plaque calcifies, it becomes visible on the CT scan because of its density. The test does not measure soft, non-calcified plaque, but the amount of hardened calcium strongly correlates with the total plaque burden.
The final measurement is presented as the Agatston score, named after its developer. This score is calculated by factoring both the area and the density of the detected calcium deposits. The total score is the sum of these weighted values from all four major coronary arteries, providing a quantitative measure of the extent of coronary artery disease.
Interpreting Specific Calcium Score Ranges
The Agatston score ranges from zero to over 1,000, with higher numbers indicating a greater amount of established atherosclerotic plaque and a higher risk of a cardiac event. The score is stratified into distinct categories to help determine a patient’s risk level.
A score of zero is associated with a very low risk of a heart attack in the short to medium term. This “double zero” status, if confirmed on a later scan, is linked to an exceptionally low 10-year risk of a coronary heart disease event. A score between 1 and 99 indicates a mild to moderate amount of plaque and represents an increased risk compared to a zero score.
The score range of 100 to 399 signifies a moderate to high plaque burden. This range suggests established coronary artery disease and a significantly higher risk of a heart attack or other event within the next three to five years. For many patients, a score above 100 is the threshold that strongly favors the initiation of preventative medication.
A score of 400 or higher indicates extensive plaque burden and a very high risk of a future cardiovascular event. Individuals in this category have a high probability of having a significant blockage in at least one coronary artery. This score often triggers a recommendation for maximal preventative therapy.
Health Implications and Follow-Up Management
The CAC score refines the prediction of cardiovascular events beyond traditional risk factors alone. The scan information is combined with a patient’s existing risk factors, such as age, cholesterol levels, and blood pressure, to create a more precise assessment of 10-year risk. The score can reclassify a patient who might have been considered intermediate risk into a higher or lower risk category.
The management strategy following a CAC scan is directly guided by the patient’s score. A score greater than zero indicates the existence of coronary artery disease, prompting a recommendation for aggressive lifestyle modifications. These changes include adopting a heart-healthy diet, establishing a regular exercise routine, and strict management of conditions like high blood pressure or diabetes.
For scores over 100, medication adjustments are typically recommended, especially for those over 400. High-intensity statin therapy is strongly supported for patients with scores over 100 due to the proven mortality benefit. The use of low-dose aspirin may also be considered for those with elevated scores, as studies show improved outcomes in this high-risk group.
A patient with a very high score, such as over 400, may require further diagnostic testing to rule out significant blockages. This may involve a stress test to determine if the heart muscle is receiving adequate blood flow during exertion. The ultimate goal of this risk stratification and subsequent management is to slow the progression of atherosclerosis and significantly reduce the likelihood of a heart attack or stroke.