A limitation of the Agatston coronary artery calcium (CAC) score is that it does not use all of the calcium density information in the computed tomography scan such that many individuals have a score of zero. We examined the predictive validity for incident coronary heart disease (CHD) events of the spatially weighted coronary calcium score (SWCS), an alternative scoring method for CAC that assigns scores to individuals with Agatston CAC=0.
The MESA (Multi-Ethnic Study of Atherosclerosis) is a longitudinal study that conducted a baseline exam from 2000 to 2002 in 6814 participants including computed tomography scanning for CAC. Subsequent exams and systematic follow-up of the cohort for outcomes were performed. Statistical models were adjusted using the MESA risk score based on age, sex, race/ethnicity, systolic blood pressure, use of hypertension medications, diabetes, total and HDL (high-density lipoprotein) cholesterol, use of lipid-lowering medications, smoking status, and family history of heart attack.
In the 3286 participants with Agatston CAC=0 at baseline and for whom SWCS was computed, 98 incident CHD events defined as definite or probably myocardial infarction or definite CHD death occurred during a median follow-up of 15.1 years. In this group, SWCS predicted incident CHD events after multivariable adjustment (hazard ratio=1.30 per SD of natural logarithm [SWCS] [95% CI, 1.04-1.60]; =0.005); and progression from Agatston CAC=0 at baseline to CAC>0 at subsequent exams (multivariable-adjusted incidence rate difference per SD of natural logarithm [SWCS] per 100 person-years 1.68 [95% CI, 1.03-2.33]; <0.0001).
SWCS predicts incident CHD events in individuals with Agatston CAC score=0 as well as conversion to Agatston CAC>0 at repeat computed tomography scanning at later exams. SWCS has predictive validity as a subclinical phenotype and marker of CHD risk in individuals with Agatston CAC=0.