Is a Calcium Score of 0 Good?
Yes, a coronary artery calcium (CAC) score of zero is excellent and indicates a highly favorable cardiovascular prognosis with an annual mortality rate of less than 1% for more than 15 years. 1
Prognostic Significance
A CAC score of zero represents the absence of detectable calcified coronary atherosclerotic plaque and confers exceptional cardiovascular protection. 1 The evidence demonstrates:
- Only 0.47% of asymptomatic patients with CAC=0 experienced adverse cardiovascular events during 50-month follow-up across 13 studies involving 71,595 patients 2
- The negative predictive value for cardiovascular events approaches 99.9%, with a pooled sensitivity of 98.1% for detecting future events 3
- An 80-year-old with CAC=0 and no risk factors has cardiovascular event risk similar to an average 50-year-old with no risk factors, effectively "de-aging" the cardiovascular system 1
The "Warranty Period" Concept
A zero CAC score provides approximately 5 years of low cardiovascular risk, though this duration may be shortened by significant risk factors. 1 Key considerations include:
- Diabetes can truncate the warranty period, with nonlinear mortality increases after 5 years despite similar 5-year outcomes 1, 4
- Persistent cigarette smoking, family history of premature atherosclerotic cardiovascular disease, and chronic inflammatory conditions also shorten the protective period 1
- For most patients with CAC=0, repeat testing is not recommended within 5 years of the initial scan 1
Clinical Management Implications
For patients with intermediate risk (7.5-20%) or borderline risk (5-7.5%) by traditional calculators, a CAC=0 reclassifies them downward into a lower risk group where statin therapy can be postponed. 1 The American College of Cardiology indicates that individuals with CAC=0 derive little or no benefit from statin therapy 1.
Important Caveats and Limitations
A zero CAC score does not completely rule out the presence of non-calcified coronary plaque, particularly in symptomatic patients. 1 Critical limitations include:
- In symptomatic patients, CAC=0 has poor correlation with coronary stenosis and should not be used to rule out obstructive coronary artery disease 5
- Among low-to-intermediate risk patients with CAC=0,25.9% still had some degree of coronary artery disease on CT angiography, with 5.1% having >50% stenosis 6
- High-risk plaque features (low-attenuation plaque, napkin-ring sign, spotty calcification) were found in 6.8% of CAC=0 patients 6
- Recent case reports document rare instances of multivessel obstructive disease in high-risk symptomatic patients despite CAC=0 7
Risk Stratification Context
The absence of coronary calcium indicates atherosclerosis burden is minimal, as CAC represents only 20% of total atherosclerosis burden since not all plaques contain calcium. 2 The European Society of Cardiology confirms that CAC=0 has a negative predictive value of nearly 100% for ruling out significant coronary narrowing in asymptomatic patients 2.
When Clinical Judgment Should Override
In symptomatic patients with high-risk features (diabetes, strong family history, multiple risk factors), additional imaging such as coronary CT angiography should be considered despite CAC=0. 7, 6 The specificity of CAC for detecting obstructive disease in symptomatic patients is only 50%, meaning it has limited ability to identify true negative cases 2.