Coronary Artery Calcium (CAC) Scoring — Diagnostics & Biomarker Testing
Non-contrast CT scan quantifying calcified plaque in coronary arteries — the strongest single predictor of future cardiovascular events, endorsed by AHA/ACC guidelines.
Overview
Coronary artery calcium (CAC) scoring uses a non-contrast CT scan to detect and quantify calcified atherosclerotic plaque in the coronary arteries, reported as an Agatston score. CAC is arguably the single most powerful predictor of future cardiovascular events in asymptomatic individuals. A CAC score of 0 confers an approximately 95% 10-year cardiovascular event-free survival. The MESA study (Multi-Ethnic Study of Atherosclerosis, n=6,814) demonstrated CAC improves risk prediction beyond the Framingham Risk Score, Pooled Cohort Equations, and all traditional biomarkers. Peter Attia considers the CAC scan the highest-value cardiovascular test available. The scan takes < 5 minutes, requires no contrast, and delivers low radiation (~0.5-1 mSv, equivalent to ~2-3 months background radiation). AHA/ACC 2018 guidelines recommend CAC scoring as a decision aid for statin therapy in intermediate-risk individuals. Low-dose CT also simultaneously screens for lung cancer.
Indications
- Cardiovascular risk stratification in asymptomatic individuals
- Statin therapy decision-making (intermediate risk group)
- Detection of subclinical atherosclerosis before symptoms
- Tracking progression of coronary artery disease
- Family history of premature coronary artery disease
Mechanism of Action
Coronary artery calcium is a direct marker of advanced atherosclerosis — calcium deposits form within lipid-rich plaques as part of the healing response to chronic inflammatory injury
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| CAC Scan | Single non-contrast chest CT | Every 3-5 years (CAC = 0); annually if CAC > 100 | Cost: $75-300 cash-pay; often not covered by insurance for screening; takes < 5 minutes |
Evidence Grade
GRADE B
Safety & Contraindications
- Low ionizing radiation dose (~0.5-1 mSv); risk of radiation-induced cancer is extremely small
- Cannot image non-calcified (soft) plaque — significant atherosclerosis may exist with CAC score of 0 in young patients
- Incidental findings on chest CT may require follow-up (pulmonary nodules, aortic aneurysm)
- Not appropriate under age 40-45 (insufficient plaque accumulation for meaningful score)
- Score of 0 does not guarantee cardiovascular safety — Lp(a)-driven events can occur without calcification