Aims: Ischaemic heart disease (IHD) mortality rates after myocardial infarction (MI) are higher in Māori and Pacific compared to European people. The reasons for these differences are complex and incompletely understood. Our aim was to use a contemporary real-world national cohort of patients presenting with their first MI to better understand the extent to which differences in the clinical presentation, cardiovascular (CVD) risk factors, comorbidity and in-hospital treatment explain the mortality outcomes for Māori and Pacific peoples.
Methods: New Zealand residents (≥20 years old) hospitalised with their first MI (2014-2017), and who underwent coronary angiography, were identified from the All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) registry. All-cause mortality up to one year after the index admission date was obtained by linkage to the national mortality database.
Results: There were 17,404 patients with a first ever MI. European/other comprised 76% of the population, Māori 11.5%, Pacific 5.1%, Indian 4.3% and Other Asian 2.9%. Over half (55%) of Māori, Pacific and Indian patients were admitted with their first MI before age 60 years, compared with 29% of European/other patients. Māori and Pacific patients had a higher burden of traditional and non-traditional cardiovascular risk factors, and despite being younger, were more likely to present with heart failure and, together with Indian peoples, advanced coronary disease at presentation with first MI. After adjustment for age and sex, Māori and Pacific, but not Indian or Other Asian patients had significantly higher all-cause mortality at one year compared with the European/other reference group (HR 2.55 (95% CI 2.12-3.07), HR 2.98 (95% CI 2.34-3.81) for Māori and Pacific respectively). When further adjusted for differences in clinical presentation, clinical history and cardiovascular risk factors, the excess mortality risk for Māori and Pacific patients was reduced substantially, but a differential persisted (HR 1.77 (95% CI 1.44-2.19), HR 1.42 (95% CI 1.07-1.83)) which was not further reduced by adjustment for differences in in-hospital management and discharge medications.
Conclusion: In New Zealand patients after their first MI there is a three-fold variation in one-year mortality based on ethnicity. At least half of the inequity in outcomes for Māori, and three-quarters for Pacific people, is associated with differences in preventable or modifiable clinical factors present at, or prior to, presentation.