CORONARY ARTERY CALCIUM IMAGING & SCORING

Coronary Artery Calcium Imaging and Scoring (CAC Score)

Coronary artery calcium (CAC) scoring is an easy, convenient, painless, non-invasive imaging technique to detect and evaluate the amount of calcium deposition in the coronary arteries (i.e. blood vessels supplying the heart muscle).  It gives an idea of whether early cholesterol plaque have begun to infiltrate the coronary arteries despite the lack of any symptoms and will likely to progress in the years to come.

The degree of calcium deposition corresponds to the severity of the atheromatous plaque and the likelihood of a heart attack (see table 1).  The higher the calcium score, the greater the risk and is used by cardiologists as one of the tools to assess and correlate with the risk of adverse cardiovascular events.  Although not directly correlated – the higher the calcium score (termed the calcium burden), the greater the chance of more severe narrowing of the coronary arteries. Conversely a low calcium score although suggests a low likelihood of significant coronary artery disease, it does not exclude the possibility of significant coronary artery narrowing as some atheroma may not have calcium in them.

Age also plays a part in influencing the calcium score.  As the age increases there will inevitably be some calcium deposition on the walls of the arteries (see table 2).

The results of your CAC score will be discussed with your cardiologist, taking into account other risk factors such as age, gender, family history of premature heart attacks, diabetes, high cholesterol and smoking.

CAC imaging continues to raise interest as a means for more personalised risk stratification beyond traditional risk factors and biomarkers.

TRANSLATION OF CALCIUM SCORE

Calcium Score

( 2, 3 )

Implication Risk of Coronary

Artery Disease

0 No identifiable plaque Very low, generally less than 5 percent
1 – 10 Minimal identifiable plaque Very unlikely, less than 10 percent
11 – 100 Definite, at least mild atherosclerotic plaque Mild or minimal coronary narrowings likely
101 – 400 Definite, at least moderate atherosclerotic plaque Mild coronary artery disease highly likely, significant narrowings possible
401 or higher Extensive atherosclerotic plaque High likelihood of at least one significant coronary narrowing

Table 1

(2) Mayo Clinic Proceedings, March 1999, Vol 74.  Findings based on EBCT data

(3) Carr JJ et al.  Evaluation of Subsecond Gated Helical CT for Quantification of Coronary Artery Calcium and Comparison with Electron Beam CT; AJR 2000;174:915-921

Age, Sex and Coronary Calcium Scoring

Age ( Years )
Percentile 40 – 45 46 – 50 51 – 55 56 – 60 61 – 65 66 – 70 > 70
MEN
10% 0 0 0 1 1 3 3
25% 0.5 1 2 5 12 30 65
50% 2 3 15 54 117 166 350
75% 11 36 110 229 386 538 844
90% 69 151 346 588 933 1151 1650
WOMEN
10% 0 0 0 0 0 0 0
25% 0.1 0.1 0.1 0.2 0.5 1 4
50% 0.1 0.1 1 1 3 25 51
75% 1 2 6 22 68 148 231
90% 3 21 61 127 208 327 698

Table 2