Troponin is a normal protein which plays an important role in the contractile apparatus of myocytes, including cardiac myocytes. The isoforms troponin I and troponin T are very specific to cardiac myocytes and not present in skeletal muscles. These proteins can be detected in the circulation 3-4 hours after myocardial infarction and have a long half-life and thus are still measurable for 10 days afterwards. The long half-life allows for the late diagnosis of myocardial infarction, however makes it difficult to detect re-infarction as can occur in acute stent thrombosis after percutaneous coronary intervention. There are a number causes of troponin elevation not related to myocardial infarction, however troponin elevation is much more sensitive than myoglobin and even creatine kinase.