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 return to normal in about 48-72 hours. This time differs from that of troponin, which stays elevated longer.
Use of CK-MB in diagnosis of an AMI varies. Some institutions have discontinued assaying CK-MB in suspected AMIs; others still use CK-MB measurements in conjunction with cTnI or cTnT. This is not because CK-MB is better, troponin is a superior biomarker. Rather, some clinicians still use CK-MB because they are familiar with it and change can be difficult to institute.
One potential, but debatable, use of CK-MB is in interventional cardiology. Because CK-MB returns to normal much faster than cardiac troponins, CK-MB measurements are sometimes used to assess any immediate ischemia associated with a cardiology intervention (such as putting in a stent or during angioplasty). When a reinfarction is suspected CK-MB measurements may help verify this as well as gauge the extent of the damage.
CK-MB results do not predict future adverse cardiac events and do not have any prognostic or risk stratification use.