Which CK isoenzyme is most specific for myocardial infarction?

Which CK isoenzyme is most specific for myocardial infarction?

• A. CK-MM
• B. CK-BB
• C. CK-MB
• D. CK-NN

Answer: (C)

The main idea is which CK isoenzyme is most specific to heart muscle and therefore most helpful in signaling myocardial injury. Creatine kinase has several forms: CK-MM in skeletal muscle, CK-BB in brain, and CK-MB in heart tissue (with a small amount in skeletal muscle). When a myocardial infarction occurs, heart muscle cells release CK-MB into the blood because their membranes are damaged. This makes CK-MB the most cardiac-specific CK isoenzyme among the options. In contrast, CK-MM can rise with skeletal muscle injury, and CK-BB is associated with brain tissue, so neither is as specific for the heart. CK-NN is not a standard marker for cardiac injury. Historically, measuring CK-MB helped diagnose MI before troponins became the preferred marker, and CK-MB’s presence in the blood reflects cardiac cell damage more reliably than the other CK isoforms.

The main idea is which CK isoenzyme is most specific to heart muscle and therefore most helpful in signaling myocardial injury. Creatine kinase has several forms: CK-MM in skeletal muscle, CK-BB in brain, and CK-MB in heart tissue (with a small amount in skeletal muscle). When a myocardial infarction occurs, heart muscle cells release CK-MB into the blood because their membranes are damaged. This makes CK-MB the most cardiac-specific CK isoenzyme among the options. In contrast, CK-MM can rise with skeletal muscle injury, and CK-BB is associated with brain tissue, so neither is as specific for the heart. CK-NN is not a standard marker for cardiac injury. Historically, measuring CK-MB helped diagnose MI before troponins became the preferred marker, and CK-MB’s presence in the blood reflects cardiac cell damage more reliably than the other CK isoforms.