The 3 in 1 combo of Myocardial infarction（cTnI/CK-MB/Myo）now is recognized as a better markers of myocardial injury. For the diagnosis of myocardial infarction, to evaluate the effect of treating thrombolytic , to evaluate re-embolization or the range of embolism and the degree of risk are of great significance that are now widely used in clinical.
The 3 in 1 combo of myocardial infarction mainly include three indicators: Troponin cTnI(is widely used to clinical detection of myocardial injury and unstable angina), Myoglobin Myo(is the early indicator of detecting myocardial infarction , generally that is used to evaluate whether patient has complications and reinfarction) , Creatine kinase isoenzyme CK-MB(that is an important indicator of diagnosing acute myocardial infarction and confirming whether patient has myocardial infarction).
Now Labnovation would introduce them to you one by one:
Troponin I（Troponin I，cTnI） Troponin Tn consists of subunit troponin C(TnC),Troponin I(TnI), Troponin T(TnT), Its physiological role is involved in controlling muscle contraction, And fibronectin regulate the interaction of actin and myosin by regulating the activity of calcium ions against the striated actin ATPase.
TnC can not be used to as a specific marker of cardiac , because the TnC in skeletal muscle and myocardium is the same. TnI and TnT have three subtypes ,fast skeletal muscle subtype, slow skeletal muscle subtype and myocardial subtype , They have different gene coding ,the expression in skeletal muscle or myocardial are respectively regulating by different gene,Such as the homology of myocardial subtype cTnI and two skeletal muscle subtype is about 40% , so CTnI is a proprietary for myocardial. CTnI concentration is very low in the normal serum, very sensitive to small myocardial injury, and hasn’t cross-reaction in the skeletal muscle damage, so cTnI has advantages of high specificity, high sensitivity and long window period . When myocardial was injured , cardiac troponin complex released into the blood, 4-6 hours later, cTnI began to rise in the blood, 12 to 24hours to peak and sustain 6-10 days.
CTnI has became the most ideal marker for myocardial infarction and now is the gold standard for the AMI diagnostic. European Society of Cardiology(ESC),American Society of Cardiology(ACC).
American Heart Association(AHA)And other international authoritative academic organizations recommend cTnI as a deterministic marker for AMI diagnosis, risk stratification and patient prognosis assessment, to help clinical development or timely adjustment of treatment.
Myoglobin（Myo）is the protein for storing oxygen in the muscle, Mainly in skeletal muscle and cardiomyocytes, is the main protein of composing skeletal muscle and myocardium , but not the unique marker of myocardia . Skeletal muscle damage, Such as polymyositis, dermatomyositis, muscle strain, etc. and the inflammatory damage of the myocardium itself, are likely to lead to increased serum concentration.Due to the relatively low molecular weight, Myo is easily released into the bloodstream when the cell breaks, Is one of the earliest myocardial markers after AMI, which is very beneficial for early eliminating AMI. After AMI ,serum’s Myo will increase in1-3 hours , 4-8 hours to reach the peak, 24-36 hours to return to normal.
Myo, the clinical significance of the assay
1.The Myo rises rapidly after chest pain occurred 2-4 hours , 4-8 hours to reach the peak,that can be used to diagnose early myocardial infarction with ECG at the same time. 2.Acute chest pain happened after 6-10 hours ,if the test value of serum’s Myo is within normal range ,we can rule out the possibility of myocardial infarction.
3.After thrombolytic therapy, myoglobin increases rapidly, or increases more than 4 times after thrombolysis 90 minutes ,which show reperfusion is successful.
4.Myo can be removed from hematoma through kidneys , renal failure can cause Myo rise, high-intensity physical exercise can also make Myo rise. Myo have high sensitivity and low specificity , the detection of positive can not diagnose AMI, but the negative results on the exclusion of AMI is very valuable, So usually, the detection of Myo and other cardiac specific markers can be used to make up Myo specific defects.
5.Myo can also be used for diagnosing reinfarction, combine with clinical, such as Myo re-elevated, that should be considered for reinfarction or infarct extension.
6. window period is too short, determination is easy to see false negative after AMI have attacked 16h.
（Creatine Kinase MB, CK-MB）
Creatine kinase(CK) is widely distributed in human cells within the enzyme protein,there is the most in muscle tissue. It consists of two subunits of M and B,forming two polymers. There are three isozymes depending on the subunit combination.
CKMB, the clinical significance of the assay 1. Any loss of myocardial cells will cause CK-MB increased, Elevated levels of CK-MB in serum suggest myocardial infarction.
2.If the CK-MB value in the plasma of the patient is continuously monitored exceeds the upper limit of the reference value or the peak of the initial hour is more than twice of the reference upper limit, and the CK-MB has increased and decreased sequence variation , Exclude other reasons ,AMI should be highly suspected
3. After AMI attack, if not thrombolytic therapy, CK-MB usually increased in 3-8 hours, 8-24 hours to reach the peak, 48-72 hours to return to normal. Thrombolytic therapy, CK-MB early and short time to reach the peak is a sign of reperfusion. In most unstable angina patients, CK-MB does not rise, even if it rises ,no more than 2 times the reference limit.
4.After thrombolytic therapy, if the thrombosis dissolved, CK-MB will have a rapid increase and decrease in the change, through repeated measurements to detect hematoma CK-MB changes ,that can help doctors determine whether thrombolytic.
5. Because other organizations also contain low concentrations of CK-MB, Acute skeletal muscle trauma, dermatitis, polymyositis and muscular dystrophy, renal failure and surgery can also lead to elevate CK-MB level ; Chronic myopathy, low levels of thyroxine, alcohol can occasionally increase CK-MB, so we should pay attention to identify myocardial infarction.
Clinical significance of combining determination of 3 in 1 combo
1. To help doctor diagnose the myocardial infarction as soon as possible and to start the treatment as soon as possible
2. contribute to the early diagnosis of acute coronary syndrome and risk stratification.
3. Detecting myocardial injury caused by heart surgery.
4. Differential diagnosis of various causes of chest pain.
5. Myocardial infarct size is estimated, after AMI, thrombolysis and the indicators of interventional therapy .
Result of Cardiac Combo
So, how to test myocardial infarction ? Take a look at the following hottest POCT reader of Labnovation.
Labnovation POCT Reader