Coronary Artery Calcium Score Less Than 100: Cardiovascular Risk Implications
A coronary artery calcium (CAC) score less than 100 indicates a low to moderate cardiovascular disease risk, with significantly lower risk of coronary events compared to scores above 100. 1
Understanding CAC Score Categories and Risk
CAC = 0: Indicates absence of detectable coronary calcification and very low cardiovascular risk (0.4% event rate over 3-5 years), serving as an excellent negative risk marker 1
CAC 1-10 (Minimal): Associated with greater non-calcified coronary plaque and total plaque volume than CAC = 0, placing these individuals at higher cardiovascular risk than those with zero calcium 2
CAC 11-100 (Mild): Represents moderate risk increase with adjusted subhazard ratio of 2.2 for myocardial infarction compared to CAC = 0 1
CAC > 100: Marks a significant threshold for substantially increased risk, with 2.2 times higher risk for all-cause mortality, 4.3 times higher cardiovascular-specific mortality, and 10.4 times higher risk of coronary heart disease compared to zero calcium score 1
Clinical Significance of CAC < 100
Risk Stratification
In large cohort studies, individuals with CAC < 100 had significantly lower cardiovascular event rates compared to those with scores > 100 1
Among patients with severe hypercholesterolemia (LDL-C ≥190 mg/dL), 82% had CAC < 100, demonstrating the heterogeneity of risk even in traditionally high-risk populations 3
CAC < 100 was associated with lower risk for atherosclerotic cardiovascular disease events compared to CAC ≥ 100 (hazard ratio 3.57 for CAC ≥ 100 vs. CAC < 100) 3
Age and Gender Considerations
Both CAC scores and percentiles are strongly predictive of cardiovascular and all-cause mortality among older adults (≥75 years), with greater risk stratification observed among females than males 4
In younger individuals without traditional risk factors, the presence of any CAC (>0) was associated with increased risk of major adverse cardiovascular events (adjusted subhazard ratio: 1.67) 1
Clinical Application of CAC < 100
Preventive Therapy Decisions
For patients with borderline or intermediate risk and CAC 1-100, CAC scoring is considered a Class IIa indicator for guiding patient-clinician discussions about initiating statin therapy 1
Finding a CAC score > 100 may trigger discussion for starting statin therapy, while CAC = 0 in intermediate-risk patients may allow deferral of statin therapy with emphasis on lifestyle modification 1
CAC scoring may be particularly valuable in middle-aged and elderly adults with optimal risk factor levels in whom predicted risk is directly linked to chronological age 1
Limitations and Considerations
Radiation exposure is a limitation of CAC scoring, though with newer dose-reduction strategies, the radiation dose is now comparable to that of mammography (approximately 1-1.5 mSv) 1
CAC scoring does not detect non-calcified plaque, which may be present especially in younger patients with early atherosclerosis 1
In symptomatic patients, absence of CAC does not exclude obstructive coronary artery disease 1
Summary of Risk by CAC Score Category
Meta-analysis findings: CAC 1-100 has summary adjusted relative risk of 2.1 (95% CI, 1.6-2.9) compared to CAC = 0 5
Risk progression: Relative adjusted subhazard ratios for myocardial infarction increase from 2.2 for CAC 1-100 to 3.8 for CAC 101-400 and 5.9 for CAC > 400 1
Low-risk marker: Among individuals with LDL-C ≥190 mg/dL (traditionally high-risk), those with CAC = 0 had significantly lower cardiovascular event rates (incidence rate 4.7 per 1000 person-years; 10-year risk 3.7%) compared to those with CAC > 0 (incidence rate 26.4 per 1000 person-years; 10-year risk 20%) 6