MB-fraction of creatine kinase in serum

Reference values ​​of the activity of MB-fraction of serum CK: 6% of total activity of CC or 0-24 IU / l.

KK in the cardiac muscle consists of two isoenzymes: KK-MM( 60% of total activity) and KK-MB( 40% of total activity).KK-MB - dimer, consists of two subunits: M( muscle) and B( cerebral).MB-fraction can not be considered strictly specific for the myocardium.3% of skeletal muscle skeletal muscle is represented by this fraction. Nevertheless, the increase in activity of KK-MB is considered to be the most specific for MI - it accounts for more than 6% of total QC( up to 25%).The increase in activity of CC-MB is observed already 4-8 hours after the onset of the disease, the maximum is achieved after 12-24 hours, on the 3rd day the activity of the isoenzyme returns to normal values ​​in uncomplicated course of MI.With the extension of the IM zone, the activity of KK-MB is increased longer, which allows to diagnose the infarction of prolonged and recurrent course. The maximum activity of KK-MB is often achieved before the maximum activity of the total QC.The degree of increase in activity of increase in QC and KK-MB corresponds to the magnitude of the affected area of ​​the myocardium. If during the first hours of the MI the patient was started with thrombolytic therapy, the peak of activity of KK and KK-MB may appear earlier than usual, which is explained by the faster elution of the enzyme from the affected area( the result of reperfusion is the restoration of the patency of the thrombosed coronary artery).

In the blood, carboxypeptidase cleaves the terminal lysines of the peptide dimer KK-MB with the formation of the two main isoforms: KK-MB.and KK-MB,. In the serum of a healthy person, the coefficient of KK-MB2 / KK-MB1 is less than or equal to 1.5.After the IM, the activity of KK-MB2 increases rapidly and the coefficient of KK-MB2 / KK-MB1 becomes more than 1.5.In clinical practice, this coefficient is used for the early diagnosis of MI and the onset of reperfusion with thrombolytic therapy.

The conducted researches have shown, that at people at electrophoretic division KK it is possible to reveal 2 types macro-KK.Macro-KK type 1 represents CC-MB associated with IgG, less frequently with IgA.In the case of electrophoresis, macro-KK type 1 is located between the KK-MM and KK-MB.It is found in 3-4% of hospitalized elderly patients, in women more often than in men. This type of QC may be present in the blood of patients for years and is not associated with any disease. Macro-KK type 2 - mitochondrial KK( oligomer mitochondrial QA).During electrophoresis, it migrates to the cathode as a KK-MB.Macro-KK type 2 indicates a serious damage to the cell, is observed in severe diseases( MI, shock, malignant tumors, hepatitis, cirrhosis, severe heart failure) and is a prognostically unfavorable sign.

Different tumors can produce CC-MB or KK-MM, which account for 60% or more of the total QC activity. In this regard, if the CK-MB is more than 25% of the total QC, it is necessary to suspect a malignant neoplasm as a reason for increasing the activity of the enzyme.

The presence of the BB fraction in the blood can simulate an increase in MB-fraction, up to exceeding the activity of MB-fraction over the total QA.CC-BB appears when the blood-brain barrier is broken( after brain operations or trauma).BB-fraction also appears with serious damage to the intestine and after childbirth( especially with caesarean section).

Increase in activity of total QA and MB fractions is revealed after operations or diagnostic manipulation of the heart. Radiation therapy of the breast area can also cause a slight hyperfermentation. Tachyarrhythmias or heart failure rarely cause a rise in activity of QA and KK-MB.

Increase in the fraction of KK-MB in some cases is possible with myocarditis and myocardial dystrophy, but it usually accounts for less than 3% of total QC.

Damage to skeletal muscles is accompanied by a significant increase in MM-fraction activity, which can "simulate" MB-fraction. With rhabdomyolysis, the diagnostic sensitivity of the study of QA activity( increased 5-fold or more) is higher than that of aldolases, AST and LDH.

Diseases and conditions accompanied by increased activity of CC and KK-MB in serum

■ Physical stress and muscle trauma.

□ Increased muscle mass as a result of exercise.

□ Physical stress( overload).

□ Surgical interventions, direct trauma, intramuscular injection.

□ Acute psychosis, acute brain damage, coma( necrosis of muscles in bedsores).

□ Spasms( epilepsy, tetanus), childbirth.

□ Severe burns;electric shock.

■ Degenerative and inflammatory lesions.

□ Muscular dystrophy.

□ Myositis( collagenoses, viral infections, trichinosis).

□ Myocarditis.

■ Toxic muscle damage.

□ Acute alcohol poisoning, white fever.

□ Exogenous intoxication( bromides, barbiturates, carbon monoxide).

□ Thetania.

□ Medications( clofibrate, bronchodilators).

□ Toxic rhabdomyolysis( heroin, amphetamines).

□ Malignant hyperthermia.

■ Metabolic muscle damage.

□ Hypothyroidism.

□ Metabolic rhabdomyolysis( hypokalemia, hypophosphatemia, hyper-perosmolar conditions).

□ Glycogenosis( type V).

■ Hypoxic muscle damage: shock, peripheral embolism, hypothermia.