title: Classification of myocardial infarction: frequency and features of type 2 myocardial infarction.
abstract: BACKGROUND
  The classification of myocardial infarction into 5 types was introduced in 2007 as an important component of the universal definition. In contrast to the plaque rupture-related type 1 myocardial infarction, type 2 myocardial infarction is considered to be caused by an imbalance between demand and supply of oxygen in the myocardium. However, no specific criteria for type 2 myocardial infarction have been established.
  
  
  METHODS
  We prospectively studied unselected hospital patients who had cardiac troponin I measured on clinical indication. The diagnosis and classification of myocardial infarction were established, and the frequency and features of type 2 myocardial infarction were investigated by use of novel developed criteria.
  
  
  RESULTS
  From January 2010 to January 2011, a total of 7230 consecutive patients who had cardiac troponin I measured were evaluated, and 4499 patients qualified for inclusion. The diagnosis of myocardial infarction was established in 553 patients, of whom 386 (72%) had a type 1 myocardial infarction and 144 (26%) had a type 2 myocardial infarction. Patients in the group with type 2 myocardial infarction were older and more likely to be female, and had more comorbidities. The proportion of patients without significant coronary artery disease was higher in those with type 2 myocardial infarction (45%) than in those with type 1 myocardial infarction (12%) (P < .001). Tachyarrhythmias, anemia, and respiratory failure were the most prevalent mechanisms causing type 2 myocardial infarction.
  
  
  CONCLUSIONS
  In a cohort of patients with myocardial infarction who were admitted consecutively through 1 year, the category of type 2 myocardial infarction comprised one fourth when diagnosed by the use of newly developed criteria. Approximately half of patients with type 2 myocardial infarction had no significant coronary artery disease.
authors.affiliation: Department of Cardiology, Odense University Hospital, Odense, Denmark.
authors.forename: Lotte
authors.initials: L
authors.lastname: Saaby
authors.forename: Tina Svenstrup
authors.initials: TS
authors.lastname: Poulsen
authors.forename: Susanne
authors.initials: S
authors.lastname: Hosbond
authors.forename: Torben Bjerregaard
authors.initials: TB
authors.lastname: Larsen
authors.forename: Axel Cosmus
authors.initials: AC
authors.lastname: Pyndt Diederichsen
authors.forename: Jesper
authors.initials: J
authors.lastname: Hallas
authors.forename: Kristian
authors.initials: K
authors.lastname: Thygesen
authors.forename: Hans
authors.initials: H
authors.lastname: Mickley
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000097:blood / Q000145:classification*; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D019210:Troponin I / Q000097:blood
chemical_list: D019210:Troponin I
keywords: Troponin; Type 2 myocardial infarction; Universal definition of myocardial infarction