Objective: To investigate the impact on the apparent incidence and classification of acute myocardial infarction (AMI) after employing the ESC-ACC-AHA-WHF 2007 Universal definition of myocardial infarction (the 2007 definition).
Setting: Retrospective cohort study in a single hospital serving a geographically well-defined population.
Methods and results: Retrospectively, the medical records for all patients hospitalized with suspected AMI during 2004 were reviewed (915 with AMI discharge diagnosis, 1037 with elevated troponin T>0.03 µg/L without AMI diagnosis, 948 undergoing revascularisation and 34 with sudden death possible due to AMI). After correcting for misclassification (49 overdiagnosed and 236 underdiagnosed AMI) the number of AMI according to the 2000 definition was 1102 (20.5% overall underdiagnosed). After reclassification to the 2007 definition the total number of AMI cases decreased with 9 patients mainly due to increase of the troponin decision limit for PCI related AMI (reducing the number of PCI related AMI from 111 to 69). The percentages of patients of each type according to the 2007 subclassification were spontaneous AMI (type 1) 88.5%; AMI due to myocardial oxygen deficit (type 2) 1.6%; sudden death without troponin elevation (type 3) 2.6%; PCI related AMI (type 4) 6.8%; and AMI after coronary artery bypass (type 5) 0.5%.
Conclusions: Employing the 2007 revision of the Universal definition of AMI did not substantially alter the apparent incidence of acute AMI substantially in our population. The level of misclassification of acute coronary syndromes after introduction of the 2007 definition may depend on the clinical acceptance of AMI subgrouping.
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