Outcomes with type 2 myocardial infarction compared with non-ischaemic myocardial injury.

Objective: To identify patients with type 2 myocardial infarction (MI) and patients with non-ischaemic myocardial injury (NIMI) and to compare their prognosis with those of patients with type 1 MI.

Methods: A retrospective observational study was performed in 1010 patients admitted to the emergency department of a university hospital with at least one troponin I test between 2012 and 2013. Participants were identified using laboratory records and divided into three groups: type 1 MI (rupture of atheromatous plaque), type 2 MI (imbalance between myocardial oxygen supply and/or demand) and NIMI (patients who did not meet diagnostic criteria for type 1 or type 2 MI). Clinical characteristics and 2-year outcomes were analysed.

Results: Patients with type 2 MI and NIMI were older, with higher proportion of women and more comorbidities than patients with type 1 MI. Absolute mortality and the adjusted risk for all-cause mortality in both groups were significantly higher than that of patients with type 1 MI (39.7%, HR: 1.41 95% CI 1.02 to 1.94, p=0.038 and 40.0%, HR: 1.54 95% CI 1.16 to 2.04, p=0.002, respectively). Patients with type 2 MI and NIMI tended to present more readmissions due to heart failure (16.5%, HR: 1.55 95% CI 0.87 to 2.76, p=0.133 and 12.3%, HR: 1.15 95% CI 0.70 to 1.90, p=0.580) and less readmission rates due to acute coronary syndrome (ACS) than patients with type 1 MI (2.1%, HR: 0.11 95% CI 0.04 to 0.31, p<0.001 and 4.3%, HR: 0.22 95% CI 0.12 to 0.41, p<0.001), CONCLUSIONS: Patients diagnosed with type 2 MI and NIMI have higher rates of mortality and lower readmission rates for ACS compared with patients with type 1 MI.