Diagnosing type 2 myocardial infarction in clinical routine. A validation study

Objective. Since 2010, myocardial infarction (MI) patients reported to the Swedish registry for MI (SWEDEHEART) are routinely classified into MI subtypes. The registry has been used to study the type 2 MI population but the MI-classification in the registry has not previously been validated. The aim of this study was to validate the type 2 MI classification in the registry. Design. A total of 772 patients diagnosed with MI in 2011 and reported to the SWEDEHEART registry were included in the study. All patients were retrospectively classified into MI type 1–5 or myocardial injury by independent reviewers strictly adhering to The Third Universal Definition of MI. This gold standard classification was compared with the classification in the registry. Results. Forty-eight (6.2%) patients were classified as type 2 MI in the registry compared with 93 (12.0%) according to the gold standard classification. A type 2 MI diagnosis was confirmed in 30 out of the 48 type 2 MI patients in the registry (PPV: 62.5%). There was a moderate rate of agreement (κ: 0.43) between the gold standard classification and the classification in SWEDEHEART in deciding a type 2 MI diagnosis. Conclusion. The SWEDEHEART registry agreed moderately with the gold standard in classifying patients with type 2 MI diagnosis. Thus, studies on patients with type 2 MI in the registry should be interpreted with caution. Since the prevalence of type 2 MI is substantially underestimated in SWEDEHEART, the registry should not be used to study the prevalence of type 2 MI.