Before troponins were used in cardiac disease diagnosis, CK-MB, an isoenzyme of creatine kinase (CK), was the marker of choice for AMI diagnosis.
CK-MB is released in circulation 4-6 hours after symptoms of an AMI and usually peaks within 24 hours. Levels of CK-MB are back to normal range in 48-72 hours. The latter is different from the cardiac troponin pattern.
Use of CK-MB in diagnosis of an AMI varies. Some institutions have discontinued assaying CK-MB in suspected AMIs; others use CK-MB measurements in conjunction with cTnI or cTnT. Because CK-MB returns to normal much faster than cardiac troponins, CK-MB measurements can be used when a reinfarction is suspected. In reinfarction, CK-MB concentration rises again after the return to baseline levels.
Currently, CK-MB results do not predict future adverse cardiac events and do not have any prognostic or risk stratification use.
