Creatine kinase (CK) is an enzyme which is present in heart muscle, skeletal muscle, and the brain. Its levels are elevated at some time in about 90%-93% of patients with acute heart diseases. Moreover, elevated levels have also been reported in heart inflammation and also in some patients with high irregular heart beats (mostly ventricular) for unknown reasons.
Hepatic damage, which frequently causes an abnormal lactate dehydrogenase (LDH) value, has no effect on creatine kinase. This is advantageous as a condition often arises in which an elevated Lactate dehydrogenase level might be due to severe hepatic passive congestion from cardiac arrest rather than from acute myocardial infarction. A number of incidences associated with mild muscle injury or severe muscle exertion affect CK values. Thus, CK values are usually higher in muscle damage, muscle inflammation, muscular dystrophy, after surgery, after moderately severe exercise (e.g., long-distance running), and in delirium convulsions.
Higher serum values are reported in about 80% of cases with hypothyroidism and with serious hypokalemic patients, due to changes induced in skeletal muscle. Creatinine kinase levels can also shoot up due to effects of alcohol on muscle. It is found that CK levels became abnormal after 24-48 hours in the majority of persons following heavy drinking as well as in most patients with delirium. However, its levels are said to be within limits in chronic alcoholics without heavy intake.
CK levels are generally increased after intramuscular injection. As therapeutic injections or mechanical shocks to the body are common, this most probably explains the elevation in CK levels. Shock or damage to muscles disturbs its level for a few days postoperatively too. CK is present in brain tissue as well as muscle but its levels differ to some extent when compared to the effect of central nervous system (CNS) disease on serum CK levels. More information about creatine kinase test
CK levels may be increased in a wide variety of conditions that affect the brain, including bacterial meningitis, encephalitis, cerebrovascular accidents, hepatic coma, uremic coma, and grand mal epileptic attacks. The degree of CK elevation varies to a marked level depending upon individual cases. Higher levels of CK in some patients of certain psychiatric diseases like schizophrenia have been already observed. Also studies reveal that levels of CK are elevated in 19%-47% of patients with uremia.
As the major source for body CK is skeletal muscle, so people with relatively low muscle mass tend to have lower normal CK levels than the average person and vice-versa. Normal CK values for different races also differ. CK can be categorized into 3 main isoenzymes viz., CK-BB which is found predominantly in the lung and brain; CK-MM is found in skeletal muscle; and the hybrid CK-MB, is found predominantly in cardiac muscle.
CK isoenzyme assays can be performed in most hospital laboratories nowadays. These various isoenzymes facilitate to detect heart damage. Hence, increased levels of CK-MB value is very helpful to know the relative index of total CK which is a parameter to decide about health status of heart.