Creatine phosphokinase (CPK/CK) is an enzyme involved in energy metabolism of muscle cells.

It has three isoenzymes:

CK‑MM (skeletal muscle)

CK‑BB (brain)

CK‑MB (cardiac muscle, small amount in skeletal muscle)

CK‑MB rises in blood following damage to heart muscle, typically within 3–6 hours after onset of chest pain.

Clinical uses include:

Diagnosing acute myocardial infarction (AMI).

Monitoring cardiac injury after surgery or trauma.

Differentiating cardiac vs. skeletal muscle damage.

Often used alongside Troponin I/T for more specific cardiac diagnosis.

Analyte: CK‑MB isoenzyme in serum.

Normal Range (varies by lab): < 5 ng/mL or < 5% of total CK.

Abnormal Findings:

Elevated CK‑MB: Indicates myocardial injury (heart attack, myocarditis, cardiac surgery).

Rapid rise and fall: Characteristic of acute myocardial infarction.

Clinical Use:

Provides a biochemical marker for heart muscle damage.

Helps confirm diagnosis of heart attack when combined with ECG and clinical findings.

Useful in monitoring reinfarction (repeat heart attack).