Answer
Coronary artery calcium scoring (CACS) is a measure of coronary artery calcification detected on EBCT or helical CT. It is a marker of the atherosclerotic plaque burden and is an independent predictor of future myocardial infarction and mortality. CACS provides incremental risk information beyond traditional risk calculators. [5, 7, 2]
To calculate a CAC score, the original Agatston method involved defining a calcified lesion as a density ≥130 Hounsfield units and an area ≥3 pixels. A score was assigned to each lesion (the product of density and area), and the total score was reached by adding up each of the calcified lesion scores. A semiautomated method is now commonly utilized, following the same principles. [5]
Cardiovascular risk stratification using calcium scoring has been widely studied, and standard categories according to cardiovascular prognosis and total mortality are as follows [8] :
CAC=0: very low risk of death (< 1% at 10 years)
CAC=1-100: low risk of death (< 10% at 10 years)
CAC=101-400: intermediate risk of death (10-20% at 10 years)
CAC=101-400 and >75th percentile for age, sex, and ethnicity: moderately high risk of death (15-20% at 10 years)
CAC >400: high risk of death (>20% at 10 years
In a large study of asymptomatic patients who underwent a coronary artery calcium (CAC) CT scan, a high CAC score predicted a higher risk of death during a mean follow-up of 12 years. Compared with individuals with a CAC of 0, those with a CAC >400 had a 1.8-fold to 3.2-fold increased risk of all-cause death and a 3.1 to 5.1-fold increased risk of CVD death. [9]
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Coronary artery calcification - CT. Cross-sectional image obtained through the heart at the level of the left anterior descending (LAD) artery. The protocol on the CT machine colors all structures with an attenuation of greater than 130 HU pink. No calcium (pink) is present in the LAD or diagonal branch.
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Coronary artery calcification - CT. Image obtained in a patient with a large amount of calcium in the left anterior descending (LAD) artery. Note that other hyperattenuating structures (eg, bone, calcified lymph nodes) are pink. During the scoring process, the radiologist must circle only those areas that correspond to one of the coronary arteries.
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Coronary artery calcification - CT. Image obtained without the threshold set to color the calcium pink. Note the large amount of calcium in the left anterior descending (LAD) and left circumflex arteries.
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Coronary artery calcification - CT. Section caudal to that in the previous image shows calcium in the left anterior descending (LAD) artery as it courses down the front of the heart. The vessel is now depicted in cross section.
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Helical non–contrast-enhanced CT reveals calcification involving the left main coronary artery.
