Which of the following is an impoant marker for myocardial infarction?

LDH is a tetrameric enzyme consisting of two monomers types: H (for hea) and M (for muscle) that combine to yield 5 LDH isoenzymes: HHHH(I1), HHHM(I2), HHMM(I3), HMMM(I4), MMMM(15). Tissue injury releases a characteristic pattern of LDH isoenzymes that can be separated by electrophoresis.The blood test most commonly used to confirm the existence of hea muscle damage is the creatine kinase/CK. CK-MB shows an increase above normal in a person's blood test about six hours after the sta of a hea attack.It reaches its peak level in about 24 hours and returns to normal in 48 to 72 hours. The peak level and the return to normal can be delayed in a person who's had a large hea attack, especially if they don't get early and aggressive treatment. Tests can measure the level of other cardiac muscle proteins called troponins specifically troponin T (cTnT) and troponin I (cTnI). These proteins control the interactions between actin and myosin, which contracts or squeezes the hea muscle. Troponins specific to hea muscle have been found, allowing the development of blood tests (assays) that can detect minor hea muscle injury ("microinfarction") not detected by CK-MB. Normally the level of cTnT and cTnI in the blood is very low. It increases substantially within several hours (on average four to six hours) of muscle damage. It peaks at 10 to 24 hours and can be detected for up to 10 to 14 days.