Clinical Significance of Elevated Creatine Kinase Isoenzymes

Cardiac Causes and Interpretation

The American College of Cardiology notes that acute myocardial infarction causes significant elevation of CK-MB, which is considered the most important biochemical marker when troponin assays are unavailable 2
The American College of Cardiology recommends considering other cardiac conditions that cause CK-MB elevation, including myocarditis, cardiac contusion, surgery, ablation, pacing, or defibrillator shocks, stress cardiomyopathy, and cardiotoxic agents 3
The American Heart Association suggests that CK-MB is typically measured by mass immunoassays, with elevation defined as measurement above the 99th percentile URL, and that sex-specific values should be employed for accurate interpretation 4
The American College of Cardiology states that CK-MB has a shorter half-life than troponin, making it useful for diagnosing reinfarction 2

The American College of Sports Medicine notes that strenuous exercise commonly increases CK levels, especially with eccentric contractions, and that lymphatic clearance affects CK kinetics, with activities that influence lymph flow potentially changing measured CK levels 5
The American College of Medical Genetics recommends considering muscular dystrophies, particularly Duchenne's muscular dystrophy, and glycogen storage diseases, such as Pompe disease, as causes of elevated CK-MB 6
The American Heart Association suggests that skeletal muscle trauma can cause nonspecific CK elevation, and that mechanical stress on muscle results in membrane damage, allowing CK to enter the bloodstream 7

The American College of Cardiology notes that a rising and/or falling pattern of CK-MB is needed to distinguish acute from chronic elevations, and that normal CK-MB levels don't exclude myocardial injury, especially in late presentations 4
The American College of Sports Medicine warns that measuring only enzyme activity rather than mass can underestimate actual muscle damage, and that pre-analytic and analytic problems can induce elevated or reduced values of cardiac markers 5
The American College of Cardiology recommends being aware of common pitfalls in CK isoenzyme interpretation, including misinterpretation of elevated CK-MB in trained athletes and the potential for pre-analytic and analytic problems to affect results 8