Markers infartus infarction – myoglobin, troponin and isoenzyme of creatine kinase

Indications. principle:

Myocarditis necrosis first revealed by signs of suffering heart muscle and especially the myocyte that includes several types of protein:

– Cytoplasmic: these are enzymes such as transaminases, creatine kinase or lacticodéshydogénase;

– To metabolic function: myoglobin, involved in muscle contractility, such as troponin and myosin.

When the necrosis results in cell lysis of myocytes, normally intracellular substances are released to the outside. Thus, in the first, the lower molecular weight proteins (PM), namely myoglobin, MW 17 800, and troponin, MW 37,000, and the isoenzyme of creatine kinase, MW 86,000 .

Technique:

Sampling 5 mL of blood on heparin tube, in a non-fasting patient.

Completed in less than 15 minutes, it allows diagnosis of myocardial infarction (MI), provided that the levy is not made before the first hour of IDM, even redo the examination in case of doubt.

Results:

Present in skeletal muscle, it is first myoglobin that is released in case of myocardial necrosis: its rate is within the first hour after cardiac injury, with a peak between the 10th and 12th hour standardization at the 24th hour.

Troponins constitute the contractile apparatus of muscle: it have three subunits: TnT is specifically heart; the rate rises to 3rd hour with up to 10 h; a second later peak exists, but standardization must be done before the 10th day (a normal rate if it is less than 0.1 mg / L and pathological if it is greater than 0.5 mg / L); maintains a significant rate after 10 days allows for retrospective diagnosis of MI.

The isoenzyme of creatine kinase is it more specific creatine kinase (CK), not as Precose as myoglobin and less specific than Troponin. Of the three isoenzymes of CK, the more efficient is the CK-MB (normal rate of 5 to 10 ug / L): elevation starts) the fourth time, the peak is located between the 10th and 24th hours, and normalization between the 3rd and 4th day.

If it is suspected myocardial injury, if myoglobin is high: it is an IDM.

If cardiac pain is suspect, if myoglobin and troponin are elevated, pain require prompt management.

In case of suspicion, must be hospitalized for treatment a patient with high levels of myoglobin: he may suffer from myocardial infarction or major muscle trauma … If in doubt about a dating IDM 10 days, even high troponin mark the old heart involvement.

The dosage of these markers finally finds its justification after thrombolysis if their rate remains high, the reversal have not been sufficiently effective.

Cost:

B60.

The dosage of myoglobin is covered by the health insurance, which is not the case of troponin assays (BHN70) and isoenzyme of CK (B50), sorted out examinations nomenclature and not reimbursed this day.

Practical advice:

High levels of myoglobin signs IDM.

An elevated troponin and myoglobin requires taking quick hospital treatment.

A false positive little be found (by CPK) in case of lipid-lowering therapy including statins.