In the past, an acute myocardial infarction (AMI) was primarily diagnosed by evaluating symptoms during the patient presentation. ECG measurement and results of enzyme assays were the only major tools available. The enzymes, creatine kinase (CK), lactate dehydrogenase (LD), and aspartate aminotransferase (AST) were assayed several times a day and often for several days to observe peak concentrations and then a return to normal levels for each enzyme. Isoenzymes of CK and LD were later added to help aid AMI diagnosis. But all of these historic enzyme tests had problems. All three of these enzymes are found in other tissues, making them non-specific markers and confounding the diagnosis.
In the 1980s, a particular isoenzyme of creatine kinase called CK-MB was discovered. Although CK-MB is not totally cardiac-specific, it was much more specific than the other enzymes available. Because of this, CK-MB quickly became the benchmark marker for acute cardiac workups.
Today, the diagnosis and monitoring for heart disease has evolved further still and is based primarily on troponin measurement for myocardial injury (although CK-MB testing is still performed for acute cardiac workups in many hospitals) and BNP or NTpro-BNP for cardiac overload or congestive heart failure (CHF). Lipoproteins and cholesterol are still used for screening and risk assessment.