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CAC Score (Coronary Calcium): Medication-Driven Changes, Normal Range, and Optimal Targets

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At a glance

  • Score of 0 / no calcified plaque detected; the comparison group in the risk study [1]
  • Score 101 to 300 / 7.73 times the adjusted coronary event risk of a score of 0 [1]
  • Score above 300 / 9.67 times the risk of a score of 0 [1]
  • Each doubling of the score / 15% to 35% higher risk of a major coronary event [1]
  • Yearly change / averaged 24.9 Agatston units in MESA, scans about 2.5 years apart [3]
  • Statins / ultrasound calcium index rose in all groups; plaque volume fell on high-intensity therapy [2]

What a CAC score measures

A coronary artery calcium score comes from a CT scan of the heart and is reported in Agatston units [1][3]. A score of 0 means no calcified plaque was detected.

What is a normal or optimal CAC score?

A CAC score of 0 means no calcified plaque was detected and served as the comparison group in the risk study. That study did not establish a treatment target or show that every person should aim for a score of 0 [1].

The study scanned 6,722 men and women with no clinical cardiovascular disease and followed them for a median of 3.8 years [1]. Compared with a score of 0, the adjusted risk of a coronary event was 7.73 times higher for scores of 101 to 300 and 9.67 times higher for scores above 300 [1]. Each doubling of the score was associated with a 15% to 35% higher risk of a major coronary event and an 18% to 39% higher risk of any coronary event [1]. These are relative risks, not absolute 10-year risk percentages or percentile thresholds.

Do statins raise the CAC score?

A post-hoc patient-level analysis pooled 8 prospective randomized trials that used serial intravascular ultrasound to measure plaque in matched coronary segments [2]. Percent atheroma volume fell by 0.6% on high-intensity statins (n=1,545) and rose by 0.8% on low-intensity statins (n=1,726) and 1.0% with no statin (n=224) [2].

The calcium index rose in all three groups: median +0.044 on high-intensity statins, +0.038 on low-intensity statins and +0.020 with no statin. The increase was significantly greater with high-intensity statins than with no statin (P=0.007) and with low-intensity statins than with no statin (P=0.03), but the high- versus low-intensity comparison was not statistically significant (P=0.18) [2]. The authors concluded that, independent of plaque regression, statins promote coronary atheroma calcification [2]. The calcium index is an ultrasound measurement; this analysis did not measure Agatston scores by CT.

Does a rising score mean the drug is failing?

In MESA, 5,682 participants had two scans about 2.5 years apart, and the yearly change in CAC averaged 24.9 Agatston units [3]. Among participants who already had CAC at baseline, progression of at least 300 Agatston units a year was associated with a hazard ratio of 6.3 (95% CI 1.9 to 21.5) for hard coronary events compared with no progression [3]. That is an observational link between progression and events, not a comparison of treated and untreated patients, and it sets no target score.

Frequently asked questions

What is a normal CAC score?
A score of 0 means no calcified plaque was detected and was the comparison group in a study of 6,722 adults, where scores of 101 to 300 carried 7.73 times the adjusted coronary event risk and scores above 300 carried 9.67 times the risk [1].
Do statins lower the CAC score?
In a pooled analysis of 8 ultrasound trials, the calcium index rose in every group, and plaque volume fell on high-intensity therapy [2]. The high-intensity group had the highest median calcium-index increase, but the difference from the low-intensity group was not statistically significant [2]. Because this was an ultrasound measure, it cannot show whether statins raise or lower CT CAC scores.
Do calcium supplements raise heart attack risk?
A 2010 meta-analysis of 15 placebo-controlled trials found, in the 5 trials with patient-level data (8,151 participants), myocardial infarction in 143 people on calcium versus 111 on placebo (hazard ratio 1.31, 95% CI 1.02 to 1.67) [5]. The increases in stroke and death were not statistically significant, and the question remains unsettled [5].
How fast does a CAC score usually change?
In MESA, the yearly change averaged 24.9 Agatston units among 5,682 participants who had two scans about 2.5 years apart [3]. Among participants who already had CAC at baseline, progression of at least 300 Agatston units a year was associated with a hazard ratio of 6.3 for hard coronary events compared with no progression [3].

References

  1. Detrano R, Guerci AD, Carr JJ, Bild DE, Burke G, Folsom AR, et al. Coronary calcium as a predictor of coronary events in four racial or ethnic groups. N Engl J Med. 2008;358(13):1336-45. Coronary calcium as a predictor of coronary events in four racial or ethnic groups
  2. Puri R, Nicholls SJ, Shao M, Kataoka Y, Uno K, Kapadia SR, et al. Impact of statins on serial coronary calcification during atheroma progression and regression. J Am Coll Cardiol. 2015;65(13):1273-1282. Impact of statins on serial coronary calcification during atheroma progression and regression
  3. Budoff MJ, Young R, Lopez VA, Kronmal RA, Nasir K, Blumenthal RS, et al. Progression of coronary calcium and incident coronary heart disease events: MESA (Multi-Ethnic Study of Atherosclerosis). J Am Coll Cardiol. 2013;61(12):1231-9. Progression of coronary calcium and incident coronary heart disease events: MESA (Multi-Ethnic Study of Atherosclerosis)
  4. Nicholls SJ, Ballantyne CM, Barter PJ, Chapman MJ, Erbel RM, Libby P, et al. Effect of two intensive statin regimens on progression of coronary disease. N Engl J Med. 2011;365(22):2078-87. Effect of two intensive statin regimens on progression of coronary disease
  5. Bolland MJ, Avenell A, Baron JA, Grey A, MacLennan GS, Gamble GD, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010;341:c3691. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis
Evidence overview for CAC Score (Coronary Calcium): Medication-Driven Changes, Normal Range, and Optimal Targets