• CK is found predominantly in the heart muscle, skeletal muscle, and brain and are elevated when these muscle or nerve cells are injured.  They can rise within 6 hours after damage and if damage does not continue, the levels peak at 18 hours after injury and return to normal in 2 to 3 days. 
• To test specifically for myocardial muscle injury electrophoresis is performed to detect the three CK isoenzymes:  CK-BB (CK1), CK-MB (CK2), and CK-MM (CK3).  The CK-MB isoenzyme portion appears to be specific for myocardial cells.  CK-MB levels rise 3 to 6 hours after infarction occurs, peak at 12 to 24 hours (if there is no further myocardial damage), and return to normal 12 to 48 hours after infarction.  One can expect to see a rise in CK-MB in patients with shock, malignant hyperthermia, myopathies, or myocarditis.  Mild elevation of CK-MB (below the threshold of positive) can occur in patients with unstable angina and will signify a increased risk for an occlusive event. 
• Increased levels of total CK may indicate:
• Diseases or injury affecting the heart muscle, skeletal muscle, and brain
• Increased levels of CK-BB isoenzyme may indicate:
• Diseases that affect the CNS (e.g., brain injury, brain cancer, cerebrovascular accident [stroke], subarachnoid hemorrhage, seizures, shock, Reye syndrome), electroconvulsive therapy, adenocarcinoma (especially breast and lung), or pulmonary infarction
• Increased levels of CK-MB isoenzyme may indicate:
• AMI, cardiac aneurysm surgery, cardiac defibrillation, myocarditis, ventricular arrhythmias, or cardiac ischemia
• Increased levels of CK-MM isoenzyme may indicate:
• Rhabdomyolysis, muscular dystrophy, myositis, recent surgery, electromyography, IM injections, trauma, crush injuries, delirium tremens, malignant hyperthermia, recent convulsions, ECT, shock, hypokalemia, or hypothyroidism.

Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5^th Ed.  St. Louis, Missouri. 2014.