Table 1.

Classification Algorithm for Myocardial Infarction. The Tromsø Study

Definite MI	Definite MI was defined by one of the following sets of conditions: Typical, atypical, or inadequately described symptoms plus a definite new infarction in ECG recordings Typical symptoms plus significantly higher myocardial enzyme and/or troponin levels Atypical or inadequately described symptoms plus significantly higher myocardial enzyme and/or troponin levels plus a probable new infarction in ECG recordings Postmortem evidence of recent MI or thrombosis
Probable MI	Probable MI was defined by one of the following sets of conditions: Typical, atypical, or inadequately described symptoms plus probable new infarction shown in ECG recordings plus moderately increased myocardial enzyme and/or troponin levels Typical symptoms plus moderately higher myocardial enzyme and/or troponin levels Atypical or inadequately described symptoms plus significantly higher myocardial enzyme and/or troponin levels Atypical or inadequately described symptoms plus moderately higher myocardial enzyme and/or troponin levels plus probable new infarction shown in ECG Sudden death with no evidence of noncoronary cause of death
Possible MI	An event that can be dated and for which secondary data of typical history in combination with ECG findings and/or echocardiography and/or autopsy are consistent with MI but for which no primary data source is available
Unstable angina	Angina at rest or minimal exertion and ST‐depression or negative T‐wave in ECG
Unclassifiable	Increase in troponins or enzymes in relation to cardiac revascularization procedures (percutaneous coronary intervention or coronary artery bypass grafting) or otherwise unclassifiable
Silent MI	In the absence of clinical symptoms that can be dated: New diagnostic Q‐wave in incidental ECG, or Evidence of MI on echocardiograph and/or multigated acquisition scan, or Evidence of MI at autopsy
No MI	The conclusion after the validation procedure is that the event does not fulfill the criteria for an acute coronary event

CABG indicates coronary artery bypass graft surgery; ECG, electrocardiography; MI, myocardial infarction; PCI, percutaneous coronary intervention.