Incidence and case fatality of acute myocardial infarction in Norway 2013-2021.

Background: Previous studies of the incidence and case fatality of acute myocardial infarction in Norway are based on administrative data that do not distinguish between myocardial infarction with ST segment elevation (STEMI) and without ST segment elevation (NSTEMI). The aim of this study was to investigate the incidence, case fatality and patient characteristics for different types of myocardial infarction in the period 2013-2021.

Material and method: The Norwegian Myocardial Infarction Registry, the Norwegian Patient Registry and the Norwegian Cause of Death Registry were linked in order to identify all patients with myocardial infarction. We calculated age-adjusted incidence and 30-day case fatality.

Results: Incidence of all types of myocardial infarction in total fell by 3.8 % per year on average (95 % CI 3.6-4.1). There was a reduction of 2.3 % (95 % CI 1.8-2.8) for STEMI, 3.1 % (95 % CI 2.8-3.4) for NSTEMI, and 6.5 % (95 % CI 5.9-7.1) for out-of-hospital deaths from myocardial infarction. Thirty-day case fatality for all types of myocardial infarction in total was 21.3 % in 2013 and 17.5 % in 2021. Case fatality for all infarctions fell by an average of 2.8 % per year (95 % CI 2.3-3.3), case fatality for NSTEMI fell by 4.4 % per year (95 % CI 3.3-5.5) per year, while case fatality for STEMI was unchanged.

Interpretation: Incidence of all types of myocardial infarction declined in the period 2013-2021. Thirty-day case fatality remains high, despite a fall in case fatality for all myocardial infarctions in total and for NSTEMI. There was no change in case fatality for STEMI.