Zero Coronary Artery Calcium Score

September 8, 2020 917 Aliza Hussain, MD Christie M. Ballantyne, MD Vijay Nambi , MD, PhD A zero calcium score is desirable, but is it enough to defer therapy given that up to one-third of events will occur in this group? A viewpoint. Multiple observational studies have demonstrated the utility of the coronary artery calcium score (CAC) in identifying individuals at higher and lower atherosclerotic cardiovascular disease (ASCVD) risk. Given the very low short-term ASCVD event rates in those with a CAC of zero, the concept of the power of zero, downrisking, and the possibility of deferring statin therapy in select individuals has emerged.1 Although CAC continues to impress in stratifying cardiovascular risk, several aspects regarding zero CAC and the deferral of therapy merit consideration. About one-fourth to one-third of the total incident cardiovascular disease (CVD) events (Table) occur in those with a CAC of zero, despite some use of lipid-lowering therapy at baseline or during follow-up (in MESA [Multi-Ethnic Study of Atherosclerosis] ≈15% at baseline and 44% during follow-up).2 Indeed, individuals with a CAC of zero who develop CVD events have been shown to have a higher prevalence of potentially modifiable ASCVD risk factors, such as diabetes mellitus, smoking, or family history of premature ASCVD (on the basis of which the American Heart Association/American College of Cardiology Guidelines on the Management of Blood Cholesterol recommend against the use of CAC to defer care in individuals with the these risk factors1). Hence, although, a CAC of zero has favorable short-term prognosis, given the lifetime risk, the long-term benefit of statin therapy cannot be discounted in these individuals. One additional concern is that nuances such as this could be missed by the practicing clinician. In fact, observational studies have not only shown lower odds of aspirin and antihypertensive medication initiation but also lower odds of smoking cessation, increasing exercise, and dietary change in individuals with a CAC of zero, despite a high prevalence of an unfavorable cardiovascular health profile in several of these individuals. Additionally, other than affecting the treatment of dyslipidemia, what else would deescalation entail? Would blood pressure targets or diabetes management also differ? Certain groups of individuals (especially younger individuals and women) require even more careful attention. The presence of CAC, especially a score of >100, is relatively rare in younger adults (Table). In the CARDIA trial (Coronary Artery Risk Development in Young Adults) cohort,3 in individuals aged 32 to 46 years, the prevalence of a CAC >0 was only 8.1%, whereas the prevalence of a CAC >100 was 1.8% (Table). Overall, ≈70% to 90% of younger patients are expected to have a CAC of zero (Table). In addition, studies evaluating the utility of CAC in young individuals have relatively short follow-up, the longest being 12 years (Table). Twelve years is not a lifetime for these young individuals whose long-term cardiovascular risk should not be discounted. Atherogenesis as a process © 2020 American Heart Association, Inc. PERSPECTIVE