Differences in coronary artery disease complexity and associations with mortality and hospital admissions among First Nations and non-First Nations patients undergoing angiography: a comparative retrospective matched cohort study.

Background: First Nations people are more likely than the general population to experience long-term adverse health outcomes after coronary angiography. Our aim was to quantify the extent of coronary artery disease among First Nations and non-First Nations patients undergoing angiography to investigate differences in coronary artery disease and related health disparities.

Methods: We conducted a retrospective matched cohort study to compare health outcomes of First Nations and non-First Nations adult patients (> 18 yr) who underwent index angiography between Apr. 1, 2008, and Mar. 31, 2012, in Manitoba, Canada. The SYNTAX Score was used to measure and compare severity of coronary artery disease between groups. Primary outcomes of all-cause and cardiovascular mortality were compared between groups using Cox proportional hazard models adjusted by SYNTAX Score results and weighted by the inverse probability of being First Nations. Secondary outcomes included all-cause and cardiovascular-related hospital admissions.

Results: The cohort consisted of 277 matched pairs of First Nations and non-First Nations patients undergoing angiography; the average age of patients was 56.0 (standard deviation 11.7) years. The median SYNTAX Score results and patient distributions across categories in the matched paired cohort groups were not significantly different. Although proportionally First Nations patients showed worse health outcomes, mortality risks were similar in the weighted sample, even after controlling for revascularization and SYNTAX Score results. Secondary outcomes showed that adjusted risks for hospital admission for acute myocardial infarction (adjusted hazard ratio [HR] 3.03, 95% confidence interval [CI] 1.40-6.55) and for congestive heart failure (adjusted HR 3.84, 95% CI 1.37-10.78) were significantly higher among First Nations patients in the weighted sample.

Interpretation: The extent of coronary artery disease among matched cohort groups of First Nations and non-First Nations patients appears similar, and controlling for baseline sociodemographic characteristics, coronary artery disease risk factors and SYNTAX Score results explained higher mortality risk and most hospital admissions among First Nations patients. Although there is a need to decrease risk factors for coronary artery disease among First Nations populations, addressing individuals' behaviour without considering root causes underlying risk factors for coronary artery disease will fail to decrease health outcome disparities among First Nations patients undergoing angiography.