From the Guidelines
A coronary artery calcium (CAC) score of zero has excellent predictive value for ruling out significant coronary artery disease and indicates a very low risk of future cardiovascular events, with less than 1% annual risk of major cardiovascular events over the next 5-10 years, even in the presence of traditional risk factors. This finding can help reclassify intermediate-risk patients to a lower risk category, potentially allowing for less aggressive preventive therapy 1. The absence of calcification does not exclude the presence of non-calcified plaque, which can still rupture and cause acute coronary syndromes. For most patients with a CAC score of zero, clinicians can reasonably defer or reduce the intensity of statin therapy, focusing instead on lifestyle modifications like regular exercise, healthy diet, smoking cessation, and blood pressure control 1.
Key Points
- A CAC score of zero is associated with a highly favorable prognosis, with low cardiac risk defined as <1% annually for cardiac death or MI 1
- Patients with a CAC score of zero have a low risk of adverse cardiovascular events, with only 0.47% experiencing an event by 50-month follow-up 1
- The predictive value of a zero CAC score diminishes over time, so reassessment may be appropriate after 5 years in patients with multiple risk factors 1
- A zero CAC score does not provide absolute immunity from coronary events, particularly in younger patients, smokers, or those with a strong family history of premature coronary disease 1
Clinical Implications
- Clinicians can use a CAC score of zero to reclassify intermediate-risk patients to a lower risk category, potentially allowing for less aggressive preventive therapy 1
- Lifestyle modifications, such as regular exercise, healthy diet, smoking cessation, and blood pressure control, should be prioritized in patients with a CAC score of zero 1
- Statin therapy can be deferred or reduced in intensity in patients with a CAC score of zero, unless other high-risk conditions are present 1
From the Research
Predictive Value of a Coronary Artery Calcium Score of Zero
The predictive value of a coronary artery calcium (CAC) score of zero is a significant indicator of low cardiovascular risk.
- A CAC score of zero confers a very low risk of death, <1% at 10 years 2.
- The absence of CAC is associated with low risk of cardiovascular events compared with any CAC > 0 in both asymptomatic and symptomatic population without coronary artery disease 3.
- A CAC score of zero is associated with freedom from major adverse cardiovascular events (MACE) 4.
Association with Cardiovascular Events
- CAC > 0 is associated with an increased risk of major adverse cardiovascular and cerebrovascular events (MACE) compared to a CAC = 0 in asymptomatic and symptomatic populations 3.
- CAC > 0 is also associated with increased risk of all-cause mortality in symptomatic and asymptomatic populations 3.
- A CAC score of zero is independently associated with MACE, with an odds ratio of 0.41 (95% confidence interval: 0.17-0.97, P = 0.041) 4.
Prevalence and Predictors of Coronary Artery Disease
- The absence of coronary calcification does not exclude the presence of coronary artery disease (CAD) or the possibility of future cardiovascular events 5.
- In patients with a CAC score of zero, the independent predictors of CAD are age >55 years, hypertension, and dyslipidemia 5.
- The presence of these predictors increases the probability of having coronary plaques to 21% 5.
Limitations and Exceptions
- A CAC score of zero can provide a false sense of reassurance, as it is possible for patients to have obstructive coronary artery disease despite a CAC score of zero 6.
- Rare cases of significant coronary artery disease with a CAC score of zero have been reported, highlighting the importance of considering other risk factors and clinical presentation 6.