Myocardial infarction redefined: the new ACC/ESC definition, based on cardiac troponin, increases the apparent incidence of infarction

OBJECTIVES: To investigate the impact of the redefinition of the diagnostic criteria for myocardial infarction on its apparent incidence in a non-selected and representative series of patients admitted with acute chest pain. DESIGN: Single centre prospective study. SETTING: Medical assessment unit and cardiology wards of an inner city university hospital. PATIENTS: 80 consecutive patients aged over 25 years admitted with suspected ischaemic acute chest pain (excluding those where the ECG indicated definite myocardial infarction). INTERVENTIONS: Measurement of concentrations of conventional cardiac biomarkers (creatine kinase and its MB isoenzyme, CK-MB) and concentrations of the highly specific diagnostic indicator of myocardial damage, cardiac troponin I (cTnI) 12-24 hours after the onset of acute chest pain. MAIN OUTCOME MEASURES: Frequency of myocardial infarction as assessed by conventional diagnostic criteria (creatine kinase and CK-MB) plus clinical symptoms of infarction, versus frequency of infarction based on high sensitivity troponin assays. RESULTS: Among patients with acute coronary syndromes but non-diagnostic ECG changes, 40% (32/80) fulfilled the new criteria for myocardial infarction using high sensitivity cTnI measurement, compared with 29% (23/80) using the conventional diagnostic criteria for myocardial infarction. CONCLUSIONS: The implications of the redefinition of myocardial infarction on patients, their care, and the use of health care resources are substantial.