• Troponin t in serum

    Reference concentrations of troponin T in serum - 0-0.1 ng / ml.

    The troponin complex is part of the muscle contractile system. It is formed by three proteins: troponin T, which forms a link with tropo- myosin( molecular weight 3700), troponin I( molecular weight 26 500), which can inhibit ATPase activity, and troponin C( molecular weight 18,000), which has a significant affinityto Ca2 +.Approximately 93% of troponin T is contained in the contractile apparatus of myocytes;this fraction may be a precursor for the synthesis of the troponin complex, 7% in the cytosol( which explains the biphasicity of the peak in increasing troponin concentration in MI).Troponin T from the cardiac muscle by amino acid composition and immune properties is different from troponin T of skeletal muscles. In the blood of healthy people, even after excessive physical exertion, the concentration of troponin T does not exceed 0.2-0.5 ng / ml, so detecting its level above this limit indicates damage to the heart muscle.

    Kinetics of troponin T in comparison with other markers of MI is presented in Table.and in Fig. Myoglobin is dissolved in the cytosol, so it rises in the blood first. Further there are KK and KK-MB, but they quickly disappear from the blood( in the first 1-2 days).LDG and LDG1 appear later and last longer.

    Table Dynamics of changes in markers IM

    Table Dynamics of changes in markers IM

    The kinetics of troponin T in MI differs from that of enzymes. On the first day, the increase in troponin T depends on the blood flow in the infarction zone. With IM, troponin T rises in the blood within 3-4 hours after the onset of the pain attack, the peak of its concentration falls on the 3rd-4th day,

    Fig. Dynamics of changes in the concentration of markers IM

    Fig. The dynamics of changes in the concentration of markers of AS AS488DD for 5-7 days is observed "plateau", then the level of troponin T gradually decreases, but remains elevated to 10-20 days.

    With uncomplicated course of MI, troponin T concentration decreases by the 5th-6th day, and by the 7th day, elevated troponin T values ​​are detected in 60% of patients.

    Specificity of determination of troponin T in blood with MI is 90-100%.In the first 2 hours after the onset of a painful attack, the sensitivity of determining troponin T is 33%, after 4 hours - 50%, after 10 hours - 100%, on the 7th day - 84%.

    The concentration of troponin T increases after the initiation of MI significantly more than the activity of CC and LDH.In some patients with successful recanalization, the concentration of troponin T can increase by more than 300 times. The concentration of troponin T in the blood depends on the size of the myocardial infarction. Thus, with large focal or transmural myocardial infarction after thrombolysis, the concentration of troponin T can be increased up to 400 times, and in patients with MI without a Q wave, only 37 times. The time to maintain a high concentration of troponin T in serum is also significantly longer than CC and LDH.The long period of release of troponin T into the blood increases the probability that the positive result of its determination was correct, especially in the subacute phase of MI."Diagnostic window"( the time during which the altered values ​​of the studied index are revealed in pathological conditions) for troponin T is more than 4 times as compared with the CC and 2 times compared with LDH.The absolute

    interval of diagnostic sensitivity for acute MI for troponin T is 125-129 h, for CK and LDH - 22 and 70 h respectively.

    Serum troponin T concentration increases in patients after heart surgery. When heart transplantation, the concentration of troponin T increases to 3-5 ng / ml and remains at an elevated level of 70-90 days.

    Non-coronary diseases and cardiac muscle lesions( myocarditis, cardiac trauma, cardioversion) may also be accompanied by an increase in the concentration of troponin T in the blood, however, the dynamics of its change, characteristic of MI, is absent.

    The serum troponin T content may increase with septic shock and chemotherapy due to toxic damage to the myocardium.

    False positive results in the determination of troponin T in serum can be obtained with hemolysis( interference), in patients with a significant increase in Ig concentration in the blood, arthritis and especially CRF, as well as in chronic muscle pathology.

    Increased troponin T concentration is possible with acute alcohol intoxication, but with chronic intoxication it is not observed.

    Slightly elevated troponin T in the blood serum is found in 15% of patients with severe skeletal muscle damage( the activity of KK-MB is increased in 50% of such patients), so troponin T can be considered a highly specific marker of MI even with skeletal muscle damage.

    Unlike the cardiac muscle, muscle T. T. is expressed in skeletal muscle. Although specific monoclonal antibodies are used to determine cardiac troponin T, cross-reactive reactions occur when large amounts of troponin T enter from the skeletal muscle.

    In patients with a troponin concentration of T 0.1-0.2 ng / ml, the risk of early complications is particularly high, so in such cases active therapy and careful monitoring in dynamics is necessary. Since only a quantitative method for the determination of troponin T makes it possible to measure the concentration in the range 0.1-0.2 ng / ml, this study has the advantage over a fast qualitative method whose sensitivity threshold is 0.2 ng / ml.