BACKGROUND: Aging is a risk factor for type 2 myocardial infarction or myocardial injury, but few data are available on the elderly. We aimed to determine the factors associated with these pathologies and mortality in the elderly population and its age classes. METHODS: A retrospective cohort of all patients with oxygen mismatch (anemia, hypoxia, tachycardia, hypo/hypertension) for whom a troponin drawn was performed at admission in 2 emergency departments. Medical records were reviewed and classified as having type 2 myocardial infarction, acute or chronic myocardial injury, or no myocardial injury. RESULTS: Of the 824 patients who presented with oxygen mismatch, 675 (81.9%) were older than 65 years. Age over 85 years was a risk factor for acute non-ischemic myocardial injury (odds ratio, 95% confidence interval 2.23, 1.34-3.73). Non-ischemic myocardial injury was associated with hypoxemia, tachycardia, and acute renal failure in those older than 85 years, but only with acute infection in the 75-84-year-old group. Type 2 myocardial infarction was associated only with acute renal failure in the oldest group and, in the 75-84-year-old group, with acute heart failure and shock. Patients older than 85 years with acute myocardial injury, with or without infarction, had a higher in-hospital mortality, but subsequently, mortality depends more on the comorbidities than on age. CONCLUSION: Factors associated with type 2 myocardial infarction and acute non-ischemic myocardial injury in elderly admitted with oxygen mismatch vary notably between age classes. They are associated with in-hospital mortality but not with subsequent mortality when other cormorbities are taken into account.