Prognostic value of coronary artery calcium scoring and computed tomography coronary angiography in remote Indigenous and non-Indigenous Australians

Background: The long-term prognostic utility of coronary calcification and coronary artery disease on computed tomography coronary angiography (CTCA) in remote Indigenous and non-Indigenous Australians is not known.

Methods: Consecutive patients undergoing CTCA from 2013 to 2017 in Central Australia were followed-up for major adverse cardiovascular events (MACE).

Results: 347 patients were included (50 ± 12 years; 47% female; 39% Indigenous). 172 (50.0%) exhibited coronary calcification. CTCA demonstrated no coronary artery disease (CAD) in 137 (39.5%), non-obstructive CAD in 149 (42.9%), and obstructive CAD in 61 (17.6%) patients. Although Indigenous ethnicity was associated with coronary calcification and baseline CAD in age- and gender-adjusted models, this association was non-significant after accounting for comorbidities. Over 4.6 years (IQR 3.52-5.68) of follow-up, MACE incidence rates per 100 person-years were 2.92 (CI 1.92-4.44) and 0.48 (CI 0.18-1.27) in those with and without calcification respectively (p = 0.001), and 0.15 (CI 0.02-1.09), 1.32 (CI 0.69-2.54), and 6.23 (CI 3.81-10.16) in patients with no, non-obstructive, and obstructive CAD respectively (p < 0.001). Coronary calcification and obstructive CAD were associated with 5-fold (HR 5.25, 95% CI 1.66-16.59, p = 0.005) and 6-fold (HR 6.35, 95% CI 2.70-14.89, p < 0.001) greater hazards of MACE respectively in multivariable models, with no significant interaction by ethnicity in these associations seen.

Conclusions: The prognostic value of coronary calcification and CAD on CTCA amongst remote Indigenous individuals appears similar to that seen in non-Indigenous populations. Our data suggest that coronary artery calcium scoring and CTCA can be used to risk-stratify in remote settings where a normal study is associated with an excellent prognosis for at least two years.