Markers of myocardial damage in acute coronary syndromes--therapeutic implications

Patients admitted with suspicion of an acute coronary syndrome (ACS) still constitute a diagnostic, prognostic and therapeutic challenge for the treating physician. The final diagnosis ranges from a noncardiac diagnosis to a full-blown myocardial infarction (MI). Biochemical markers of myocardial damage are essential for diagnosis and, especially troponin T and troponin I, have been shown to be valuable for early risk stratification and for selection of treatment in ACS. Patients identified to be at low risk of future cardiac events might be discharged early, and unnecessary investigations and treatments avoided. On the contrary, a more intense treatment can be started in patients identified to be at high risk. Unstable angina patients with, compared to without, elevation of troponin, have a more activated coagulation system and more frequently complex lesions and visible thrombus in their coronary arteries. Accordingly, antithrombotic and antiplatelet therapies, i.e. l.m.w heparin and GP IIb/IIIa receptor antagonists, have been proved to have beneficial effects in troponin positive patients, but little or no beneficial effects in troponin negative patients. Also, the beneficial effects of an invasive compared to a noninvasive approach seem to be much more pronounced in troponin positive patients. In patients with ST-elevation MI, an elevated troponin T level at admission are associated with an increased mortality. However, the therapeutic implications of this finding remain speculative. Patients admitted with chest pain and left bundle branch block (LBBB) and who develop an MI have a poor prognosis. Current guidelines in acute myocardial infarction state that these patients should receive thrombolysis. Despite that, only a minority of these patients do receive thrombolysis, most probably because of the great diagnostic uncertainty. Rapid testing with a cardiac marker, e.g. myoglobin, would most probably increase the proportion of patients with chest pain and LBBB who receive appropriate reperfusion treatment.