<Tr> <Td> Troponin test </Td> <Td> The most sensitive and specific test for myocardial damage . Because it has increased specificity compared with CK - MB, troponin is a superior marker for myocardial injury . </Td> <Td> 12 hours </Td> <Td> Troponin is released during MI from the cytosolic pool of the myocytes . Its subsequent release is prolonged with degradation of actin and myosin filaments . Isoforms of the protein, T and I, are specific to myocardium . Differential diagnosis of troponin elevation includes acute infarction, severe pulmonary embolism causing acute right heart overload, heart failure, myocarditis . Troponins can also calculate infarct size but the peak must be measured in the 3rd day . After myocyte injury, troponin is released in 2--4 hours and persists for up to 7 days . </Td> </Tr> <Tr> <Td> Creatine Kinase (CK - MB) test </Td> <Td> It is relatively specific when skeletal muscle damage is not present . </Td> <Td> 10--24 hours </Td> <Td> The CK - MB isoform of creatine kinase is expressed in heart muscle . It resides in the cytosol and facilitates movement of high energy phosphates into and out of mitochondria . Since it has a short duration, it cannot be used for late diagnosis of acute MI but can be used to suggest infarct extension if levels rise again . This is usually back to normal within 2--3 days . </Td> </Tr> <Tr> <Td> Lactate dehydrogenase (LDH) </Td> <Td> LDH is not as specific as troponin . </Td> <Td> 72 hours </Td> <Td> Lactate dehydrogenase catalyses the conversion of pyruvate to lactate . LDH - 1 isozyme is normally found in the heart muscle and LDH - 2 is found predominantly in blood serum . A high LDH - 1 level to LDH - 2 suggest MI . LDH levels are also high in tissue breakdown or hemolysis . It can mean cancer, meningitis, encephalitis, or HIV . This is usually back to normal 10--14 days . </Td> </Tr> <Tr> <Td> Aspartate transaminase (AST) </Td> <Td> </Td> <Td> </Td> <Td> This was the first used . It is not specific for heart damage, and it is also one of the liver function tests . </Td> </Tr>

Which of the following biomarkers is most specific to cardiac muscle damage