What is a total coronary calcium score used for?

Coronary Calcium Score: A Powerful Tool for Cardiovascular Risk Assessment

The total coronary calcium score is primarily used to quantify coronary artery calcification as a marker of atherosclerosis burden and to predict future cardiovascular events in asymptomatic individuals, particularly those with intermediate cardiovascular risk, helping guide decisions about preventive interventions such as statin therapy. 1, 2

What is a Coronary Calcium Score?

• A coronary calcium score is a quantitative measurement of calcium deposits in coronary arteries detected through electrocardiogram-gated multidetector computed tomography (CT) scanning 1, 2
• The Agatston score is the most widely used scoring system, which quantifies calcific lesions with CT density >130 Hounsfield units and area >1 mm² 1
• The radiation dose is relatively low (approximately 0.37-1.5 mSv), comparable to or slightly lower than screening mammography (0.44-0.56 mSv) 1, 2

Clinical Utility and Risk Prediction

• CAC is a robust marker for risk assessment and prediction of future atherosclerotic cardiovascular disease (ASCVD) events in asymptomatic patients without known coronary artery disease 1
• CAC is superior to traditional risk-factor assessments and other nontraditional markers (e.g., carotid intimal thickness, ankle-brachial index, C-reactive protein) for predicting cardiovascular risk 1
• Cardiovascular risk increases proportionally with calcium score, especially when scores exceed 300-400 1, 3
• A calcium score of zero (CAC=0) indicates excellent prognosis with very low risk (<1% annually) for cardiac death or myocardial infarction - known as "the power of zero" 1, 4

Guidelines for Clinical Application

• The 2019 ACC/AHA preventive guideline recommends CAC scoring as a reasonable guide for shared decision-making in adults aged 40-75 years with intermediate ASCVD risk (7.5-20%) or selected adults with borderline risk (5-7.5%) 1, 2
• Patients with intermediate risk but no coronary calcification can be reclassified into a lower-risk group, potentially avoiding statin therapy 1
• The ACC/AHA 2010 guidelines recommend screening for clinically silent ischemia when calcium scores exceed 400 1

Important Clinical Considerations

• CAC should be seen primarily as a marker of atherosclerosis burden and not of degree of stenosis 1, 2
• In symptomatic patients, a calcium score of zero does not exclude obstructive coronary artery disease, as noncontrast CT does not detect noncalcified atherosclerotic plaque 1
• The distribution of calcium across coronary arteries provides additional prognostic information - mortality risk is higher when calcification is present in the left main coronary artery 1
• Due to radiation exposure and low prevalence of calcification in younger individuals, calcium scoring is generally not recommended for men under 40 and women under 50 years of age 2

Limitations and Controversies

• While CAC scoring adds incremental value to traditional risk assessment, the modest gain (pooled increase in C-statistic of 0.036) may be outweighed by costs, incidental findings, and radiation risks in some patients 5
• False reclassification can occur - among patients reclassified to higher risk categories by CAC, 85.5-96.4% did not experience cardiovascular events during follow-up periods of 5.1-10 years 5
• There is ongoing debate about whether adding CAC to traditional risk scores provides sufficient clinical benefit to justify routine use 5, 6