Short term prognosis of patients with acute coronary syndromes: the level of cardiac troponin T elevation corresponding to the "old" WHO definition of myocardial infarction.
T raditionally, myocardial infarction (MI) has been diagnosed according to the World Health Organization criteria, which emphasises the importance of the clinical syndrome, electrocardiographic changes, and elevation of long standing but relatively non-specific markers of myocardial damage such as creatine kinase (CK). In 2000, a Joint European Society of Cardiology (ESC)/ American College of Cardiology (ACC) committee published a redefinition of MI, based upon raised serum concentrations of cardiac troponins. This has led to the inclusion of patients with lower levels of myocardial damage than was previously detectable. As a result future epidemiological studies will inevitably be skewed by the ‘‘new’’ definition with an increase in the numbers of patients diagnosed with MI, and an apparent improvement in overall prognosis likely to be related to a smaller proportion of patients with large transmural infarctions being exposed to the hazards of ventricular remodelling and heart failure. This has important implications for patients who may be unjustifiably concerned by information concerning their prognosis obtained from historical studies and unjustifiably penalised by financial institutions. For these reasons it is important to try and establish the level of troponin elevation that corresponds in terms of prognosis to the ‘‘old’’ WHO definition of MI so that patients and physicians can compare old and new data from registries and clinical trials.