What laboratory marker is primarily used to assess the severity of myocardial infarction?

The severity of a myocardial infarction (heart attack) is primarily assessed using levels of creatine phosphokinase (CPK), specifically the CPK-MB isoenzyme. When cardiac muscle sustains damage during an infarction, CPK is released into the bloodstream. Elevated CPK-MB levels are indicative of myocardial injury and are correlated with the extent of damage to the heart muscle. This makes CPK levels a crucial laboratory marker in the diagnosis and evaluation of heart attacks, as they reflect the specific injury to cardiac tissues over time.

Other laboratory markers like blood glucose levels, white blood cell count, and platelet count may provide supportive information regarding a patient's overall health or additional conditions but are not specific indicators for assessing the severity of myocardial infarction. Blood glucose might reflect stress or metabolic status; white blood cell count can indicate inflammation or infection; and platelet count is more closely related to clotting disorders rather than direct myocardial damage. Thus, they do not serve as primary markers for evaluating myocardial infarction severity.