Abstract 4366893: Effects of Concordance and Discordance of Coronary Calcium Density and Volume on Major Adverse Cardiac Event Outcomes

Introduction: Coronary artery calcium (CAC), quantified by the Agatston score on cardiac CT, is a well-established measure of atherosclerotic burden. While the Agatston score combines both plaque density and area, emerging evidence suggests these components and their discordance may enhance risk stratification. Research Question: What is the relationship between concordant and discordant calcium density and volume for the prediction of major adverse cardiovascular events (MACE) in asymptomatic individuals with prevalent CAC? Methods: This retrospective study included CAC CT scans of asymptomatic individuals without known history of atherosclerotic cardiovascular disease and not on lipid-lowering therapy (2010-2023). Included patients had prevalent CAC and at least 3 years of follow-up. A validated convolutional neural network quantified total Agatston score, mean plaque density, and total calcium volume. MACE outcomes were determined via ICD and CPT codes. Two concordant and two discordant groups were made with median values of the study population as cutoffs: (1) high density/high volume, (2) high density/low volume, (3) low density/high volume, and (4) low density/low volume. Time-to-event outcomes were analyzed using cumulative incidence curves and hazard ratios (HR) via Cox regression. Results: The study included 2,647 patients (mean age 60 (±9) years; 36% women; 9% Black). Mean follow-up time was 5.5 (±2.2) years. MACE occurred in 263 patients (9%). Median Agatston score was 46 (IQR 8-198), median calcium density was 195HU (IQR 165-224HU), and median calcium volume was 49mm3 (IQR 14-187mm3). Of the four groups, 37% (978) had high density/high volume, 13% (345) had high density/low volume, 13% (345) had low density/high volume, and 37% (979) had low density/low volume. The cumulative incidence curves demonstrate that patients with high calcium volume—regardless of density—had higher rates of MACE. High volume groups were significantly more predictive of MACE than low volume groups (high density/high volume: HR: 2.05 (95% CI:1.52-2.77), low density/high volume: HR: 2.04 (95% CI:1.39-3.01) high density/low volume: HR: 0.85 (95% CI:0.52-1.40), compared to the low density/low volume group). Conclusion: Calcium volume, independent of concordance and discordance with calcium density, was the strongest predictor of MACE. Further investigation into calcium characteristics may refine the ability to predict MACE and guide personalized prevention strategies.