Evolving Role of Coronary Artery Calcium Testing

In a rapid-fire oral abstract session that I moderated, a few studies explored ways to extend the use of CAC testing beyond the Cholesterol Guidelines algorithm. One study from the MESA cohort demonstrated that among individuals with risk-enhancing factors (i.e., family history of CVD, metabolic syndrome, etc.), there was a wide range of CAC scores and a relatively low risk of ASCVD events if the CAC score was 0 despite risk-enhancing factors. This study raised the question if CAC testing should move up to the second step in the risk assessment algorithm. Another study from the CAC Consortium investigators evaluated the prevalence of CAC >0 in 20- to 30-year-olds, a group well below the traditional screening age for CAC scanning. Among 373 subjects, 13% had detectable CAC. The strongest risk factors for the presence of CAC in this study were hyperlipidemia and a family history of CVD. While the prevalence of CAC might be enriched in this referral cohort, and broad screening of this younger age group is not appropriate, this study corroborates other studies that have shown a non-negligible amount of CAC in select individuals under age 40. Future algorithms may elucidate which young individuals may be most appropriate for CAC testing. 

Finally, a study we presented using the Dallas Heart Study examined if CAC can be used to determine who would benefit from aspirin therapy in primary prevention. The recent 2019 Prevention Guidelines downgraded aspirin to a IIb recommendation for this indication, acknowledging the increased risk of major bleeding of aspirin and net harm for most people. Among the 2,191 individuals in our study, we observed that higher CAC scores not only correlated with increased ASCVD events but also with increased hospitalized bleeding events. 

In fact, taking into account these observed 10-year risks and modeling the effects of aspirin from recent meta-analyses, we found that even among those with high CAC scores (>300), aspirin therapy would cause important bleeding events in more people than those who potentially would benefit from a reduction in ASCVD events. Thus, CAC scanning might not help discriminate net benefit from aspirin therapy. 

Coronary artery calcium testing has a valuable role in shared decision-making for preventive interventions. The 2018 Cholesterol Guidelines paved the way for studies, similar to the ones above, to clarify and potentially expand the role of CAC scanning.