The morbidity and mortality outcomes of indigenous Australian peoples after isolated coronary artery bypass graft surgery: the influence of geographic remoteness

Abstract

Background: Though Indigenous Australian peoples reportedly have poorer survival outcome after cardiac surgery, few studies have jointly documented the experience of major morbidity, and considered the influence of patient geographic remoteness.

Methods: From January 1998 to September 2008, major morbidity events and survival were recorded for 2748 consecutive patients undergoing coronary artery bypass graft surgery. Morbidity and survival analyses adjusted for propensity deciles based on patient ethnicity and age, sex, left ventricular ejection fraction, recent myocardial infarction, tobacco smoking, diabetes, renal disease and history of stroke. Sensitivity analyses controlled for the patient accessibility/remoteness index of Australia (ARIA).

Results: The 297 Indigenous Australian patients (10.8% of total) had greater odds for total morbidity (adjusted odds ratio = 1.55; 95% confidence interval [CI] 1.04-2.30) and prolonged ventilation (adjusted odds ratio = 2.08; 95% confidence interval [CI] 1.25-3.44) in analyses adjusted for propensity deciles and geographic remoteness. With a median follow-up of 7.5 years (interquartile range 5.2-10.2), Indigenous Australian patients were found to experience 30% greater mortality risk (unadjusted hazard ratio = 1.30; 95% CI: 1.03-1.64, p = 0.03). The effect size strengthened after adjustment for propensity score (adjusted hazard ratio = 1.49; 95% CI: 1.13-1.96, p = .004). Adjustment for ARIA categorisation strengthened the effect size (adjusted HR = 1.54 (95% CI: 1.11-2.13, p = .009).

Conclusion: Indigenous Australian peoples were at greater risk for prolonged ventilation and combined morbidity outcome, and experienced poorer survival in the longer term. Higher mortality risk among Indigenous Australians was evident even after controlling for remoteness and accessibility to services.

Keywords: Aborigines; Australian; CABG; Cardiac surgery; Indigenous Population; LVEF; MI; Survival Analysis; coronary artery bypass graft; left ventricular ejection fraction; myocardial infarction.