Does Coronary Artery Calcification Classify as Coronary Artery Disease?
Yes, coronary artery calcification (CAC) is definitively a marker of coronary artery disease—calcification does not occur in normal vessel walls and signifies the presence of atherosclerosis. 1
Understanding the Relationship Between CAC and CAD
CAC as a Direct Marker of Atherosclerosis
Coronary calcifications represent atherosclerosis of the coronary arteries and are exclusively present in atherosclerotic lesions of the intimal layer. 2
Calcification does not occur in a normal vessel wall, thus signifying the presence of atherosclerosis; the presence of any CAC highly correlates with the presence of CAD except in certain metabolic conditions such as diabetes, uremia, and disorders causing calcium-phosphate homeostasis imbalance. 1
CAC is a reliable marker of coronary atherosclerosis and vascular age, with autopsy studies showing that histological plaque areas and CT CAC areas are highly correlated at the level of coronary segments, individual coronary arteries, and the heart as a whole. 1
Critical Distinction: Atherosclerosis vs. Obstructive Disease
The most important clinical caveat is that while CAC confirms the presence of CAD (atherosclerosis), it does NOT necessarily indicate obstructive coronary artery disease or hemodynamically significant stenosis. 1, 2
CAC should be viewed primarily as a marker of atherosclerosis burden rather than degree of stenosis, as lumen patency is often preserved by vascular remodeling with limited correlation between residual luminal areas and calcified areas. 1, 3
The CAC area represents only 20% of the total atherosclerosis burden because not all plaques contain calcium. 1, 3
CAC testing is not appropriate as a surrogate for angiographic disease detection because of the modest relationship between CAC and obstructive coronary artery disease—calcium testing was not recommended in the 2000 ACC/AHA expert consensus document to diagnose obstructive CAD because of its low specificity. 1
Clinical Implications and Risk Stratification
Prognostic Value
The coronary artery calcium score is a robust marker for evaluating risk and predicting future cardiovascular events in asymptomatic patients, with cardiovascular risk increasing proportionally to the calcium score. 2
CAC is consistently the single best predictor of atherosclerotic cardiovascular disease (ASCVD) risk compared with other nontraditional markers such as carotid intimal thickness, ankle-brachial index, and C-reactive protein. 1
In asymptomatic patients with high CAC scores (≥1000), the overall death or myocardial infarction rate is approximately 17.9%, warranting aggressive preventive interventions. 3
Symptomatic vs. Asymptomatic Patients
For symptomatic patients with high probability of CAD, the absence of coronary calcification does not exclude obstructive stenosis—a zero CAC score was associated with myocardial ischemia on provocative testing in 16% of patients with intermediate to high risk of coronary disease. 1
In asymptomatic patients, a zero calcium score indicates an excellent prognosis with a very low risk (<1% annually) of cardiac death or myocardial infarction. 2
However, in symptomatic patients, a zero calcium score does not completely exclude obstructive coronary artery disease, as non-calcified atherosclerotic plaques are not detected by non-contrast CT. 2
Common Pitfalls to Avoid
Do not equate the presence of CAC with hemodynamically significant stenosis—functional testing is required to determine if calcified lesions are causing ischemia. 1, 2
Do not dismiss CAC even if traditional risk calculators suggest low risk—CAC may reclassify a patient from low or intermediate risk to high risk regardless of traditional risk factors. 4
Coronary calcifications are not an indicator of plaque stability or instability—the relationship between CAC and plaque vulnerability remains incompletely understood. 2, 3
Poor image quality, severe calcifications, and non-expert interpretation can lead to overestimation of stenosis severity on coronary CT angiography due to blooming artifacts. 2
Summary Statement
In clinical practice, CAC definitively indicates the presence of coronary atherosclerosis (CAD), but requires functional assessment or invasive angiography to determine if obstructive disease or ischemia is present. 1, 2 The degree of calcification correlates with total atherosclerotic burden and future cardiovascular risk, making it an invaluable tool for risk stratification in asymptomatic patients, but it should not be used as a standalone diagnostic test for obstructive CAD in symptomatic individuals. 1, 2