Cardiac Bio Markers

LAB DIAGNOSIS OF MYOCARDIAL INFARCTION:

Cardiac markers are useful in diagnosis of M.I.

Cardiac markers

Creatine Kinase:

It is an enzyme that is highly concentrated in brain, myocardium and skeletal muscle. It is composed of 2 dimers M and B. CK-MM is predominantly in skeletal muscle and heart CK-BB is in brain, lung. CK-MB is principally in myocardium. Total CK activity tends to rise within 24 hrs of myocardial infarction peaks at 24 hrs and returns to normal within 72 hrs. The specificity for detection of myocardial infarction is the measurement of CK-MB fraction that rises in 2-4 hr, peaks at 18 hrs and disappears by 48 hrs. In acute myocardial infarction , total    CK is 500-2000 units/ litre. CK is increased in muscle diseases like polymyositis and dystrophies.

Lactate Dehydrogenase:

It is a myocardial enzyme used to evaluate suspected myocardial infarction, Total LDH activity begins to rise with in 24 hrs of myocardial infarction, peaks at 72 hrs and persists for about a week. The isoenzymes are LDH 1-5. Normally LDH 2 is greater than LDH 1 while in acute myocardial infarction LDH 1 is greater than LDH 2. This is called LDH flip. LDH is increased in myocardial infarction, muscle disease, liver disease and malignancy.

Myoglobin:

It is an oxygen binding protein of cardiac and skeletal muscle. It is an early marker of detection with in 2-4 hrs. It rises in acute myocardial infarction, angina without infarcts. It has a poor clinically specificity.

Troponin:

These are contractile proteins of myofibrils. Different isoforms of these proteins exist. By use of sensitive immonologic assays, it has been possible to distinguish cardiac troponin I and troponin T from troponins of skeletal muscle. Cardiac troponin I is not detected in serums after pure skeletal muscle injury. It is therefore reliable marker of myocardial necrosis. Troponin levels remain elevated for 4-7 days after an acute attack  allowing diagnosis of MI long after CK-MB levels have returned to normal.

Cardiac markers1

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