The availability of 'new' biochemical markers of myocardial injury suc
h as creatine kinase isoforms and troponins has renewed the interest f
or rapid confirmation/exclusion of myocardial infarction in patients p
resented to the hospital for suspected acute myocardial ischemia. Many
of these protein markers have the potential to allow the diagnosis of
acute myocardial infarction at a time from the onset of symptoms when
the activity of creatine kinase MB is still within the reference rang
e. However, the exclusion of classical myocardial infarction as define
d by WHO criteria does not allow to conclude that the patient is at lo
w-risk and can be safely sent home since he may have high-risk unstabl
e angina. The sensitivity for the detection of myocardial damage of tr
oponins is such that a substantial proportion of patients with unstabl
e angina develop elevations of troponins in the absence of creatine ki
nase MB increases. It is now clear that such patients have an increase
d risk of cardiac events over the short and long-term similar to that
of patients with definite myocardial infarction. Such finding may help
in developing selective admission policies and deciding which patient
s deserve aggressive treatment. (C) 1998 Elsevier Science Ireland Ltd.