Enzymes serving as markers for cardiac disease:
- Creatine kinase (CK): it is present as a dimer and has two subunits – M and B. Thus three isoenzymes are found CK(MB), CK(BB), and CK(MM).
CK( MM) is the skeletal muscle form and gets increased during muscle disease like rhabdomyolysis.
CK( MB) is cardiac muscle form and gets increased during myocardial infraction.
CK(BB) is brain form and is found to be increased during brain damage.
More commonly CK measurements reflects MM isoenzyme type and its normal level is 4-60 IU/L.
- Lactate dehydrogenase (LDH): Is is a tetramer and has got five isoenzymes like HHHH, HHHL, HHLL, HLLL, LLLL. They are also known as LDH1, LDH2 to LDH5. LDH 1 is increased during cardiac muscle injury and LDH5 during liver disease. Its normal value is 200-300 IU/L.