Since its introduction into the clinical environment in the early nineties, the cardiac enzyme troponin has significantly changed the way we diagnose and manage acute coronary syndromes. Troponin I is a biochemical marker of myocardial injury with a high level of specificity and sensitivity. It has been demonstrated that as ischaemia progresses, troponin I is degraded predictably into smaller and smaller fragments that can be detected in the blood-stream. This may eventually allow more accurate determination of the duration of ischaemia and the likelihood of myocardial salvage and recovery.