Title: 376 Long-Term Prognostic Value of Coronary Artery Calcium in Indigenous and Non-Indigenous Australians
Abstract: Ethnic differences in the presence and quantity of coronary calcification has been suggested by prior studies. However, there is little data in Indigenous populations, and it is not known whether coronary artery calcium similarly predicts prognosis in Indigenous compared to non-Indigenous individuals. Consecutive patients undergoing computed tomography coronary angiography (CTCA) in Central Australia between 2013-2017 were included and followed for cardiac events (death, non-fatal myocardial infarction, and revascularisation). Coronary calcium was quantified using the Agatston score. 347 individuals were included, of whom 124 (39%) identified as Indigenous. Indigenous patients were younger (44±11 vs 54±12, p=0.001) and had a higher prevalence of hypertension and diabetes (p=0.001 for both). Coronary calcification prevalence was similar in Indigenous and non-Indigenous individuals (45% vs 53%, p=0.14). Median Agatston score was not significantly different (0 [0-42] vs 2 [0-81], p=0.13). Twenty-six cardiac events occurred after a median follow-up of 4.6 years. Increasing Agatston score predicted MACE (1.01 [1.00-1.01], p=0.001), with no ethnic difference (p=0.95). Compared to those with no calcification, those with Agatston scores 1-100 and >300 had a 4.35-fold and 11.61-fold higher hazard of cardiac events (p=0.012 and p=0.001). In multivariate analyses adjusted for ethnicity and the presence of coronary artery disease on CTCA, increasing Agatston score remained associated with cardiac events (p=0.018). Despite a higher burden of traditional cardiovascular risk factors, Indigenous individuals had a similar prevalence and extent of coronary calcification in this study. Coronary calcium identified provided similar long-term prognostic information in both Indigenous and non-Indigenous individuals.