Short- and Long-Term Indigenous Australian Cardiac Surgery Outcomes

Purpose: Indigenous Australians are over-represented in cardiac disease despite health policy advancements. Indigenous Australians present for cardiac surgery at significantly younger age and with a greater burden of co-morbidities than non-Indigenous people. As a result, current risk stratification models under-estimate Indigenous patient risk. The primary aim of this study is to determine the predicted mortality risk conveyed by an ethnic weighting, Indigenous status, at 30-days postoperatively when used in combination with the AusSCORE model of perioperative risk (PROM). The secondary aim is to determine the long-term survival of Indigenous Australians after cardiac surgery. Methodology: A retrospective case audit was performed identifying 4388 cases from 1/1/2005 to 31/12/2015. 30-day mortality risk was calculated using AusSCORE variables with the re-construction of a multivariate model using logisitic regression and incorporating the risk that Indigenous status conveys. Kaplan-Meier survival analysis was used to determine long-term outcomes. Mortality outcome data was collected by 30-day and 6-month follow-up phone call, Flinders Medical Centre Patient Administration System, National Death Index and Northern Territory Clinic Database. All statistical analysis was performed using SPSS Ver. 23. Significance was set at p = 0.05. Results: 662 patients were Indigenous. Indigenous status showed increased risk of 30-day mortality when calculated in combination with the AusSCORE PROM variables. The increase was not significant, but trended towards higher mortality at 30-days (OR 2.26, p = 0.061, AUC = 0.77) when compared to non-Indigenous patients. Kaplan-Meier analysis up to 2000 days demonstrated significant disparity in early and late survival in those Indigenous patients aged < 55yrs (Log Rank < 0.001 and Breslow < 0.001). Indigenous patients ≥55 years showed no significant difference in early or late survival (Log Rank = 0.693 and Breslow = 0.642). Conclusion: This is the largest single centre review of Indigenous cardiac surgery outcomes to date. It has demonstrated that Indigenous patients have a 2.26x, but statistically non-significant higher chance of mortality than non-Indigenous patients at 30-days when Indigenous status is used in combination with the AusSCORE model for PROM. < 55yrs Indigenous Australians also have reduced long-term survival being most apparent after 1500-days. This is not seen in the ≥55yrs cohort.