Your Federal Quarterly Tax Payments are due April 15th Get Help Now >>

Biochemical Markers for Diagnosis of Myocardial Infarction by malj


									      Cardiovascular Block
 Medical Biochemistry Course

Biochemical Markers
     for Diagnosis of
Myocardial Infarction
      Dr. Reem M. Sallam, MD, PhD.
  What is Myocardial Infarction?
• Myocardial ischemia results from the reduction of coronary
  blood flow to an extent that leads to insufficiency of oxygen
  supply to myocardial tissue

• When this ischemia is prolonged & irreversible, myocardial
  cell death & necrosis occurs ---this is defined as:
                      myocardial infarction

       is the death & necrosis of myocardial cells
    as a result of coronary prolonged & irreversible
   Biochemical Changes in Acute Myocardial Infarction
       (mechanism of release of myocardial markers)
           ischemia to myocardial muscles (with low O2 supply)

                            anaerobic glycolysis

                     increased accumulation of Lactate

                               decrease in pH

                        activate lysosomal enzymes

                    disintegration of myocardial proteins

                            cell death & necrosis

clinical manifestations      release of intracellular             ECG
     (chest pain)               contents to blood                changes
Diagnosis of Myocardial Infarction

 SHOULD depend on THREE items
   (as recommended by WHO)

      1- Clinical Manifestations
      2- ECG
      3- Biochemical Markers
                 criteria for ideal markers
                  for myocardial infarction
1- Specific:    to myocardial muscle cells (no false positive)

2- Sensitive:    - rapid release on onset of attack (diagnose early cases)
                 - so, can detect minor damage
                 - no miss of positive cases (no false negative)

3- Prognostic: relation between plasma level & extent of damage

4- Persists longer: so, can diagnose delayed admission

6- Reliable: procedure depends on evidenced principle

5- Simple, inexpensive:      - can be performed anywhere by low costs
                             - no need for highly qualified personnel

7- Quick: low turnaround time
Types ofBiochemical Markers for
       Myocardial Infarction
1- Cardiac Enzymes (isoenzymes):
      Total CK
      CK-MB activity
      CK-MB mass

2- Cardiac proteins:
               Cardiac Enzymes
• Total CK          (sum of CK-MM, CK-MB & CK-BB)
  non specific to cardiac tissue (available in skeletal ms.)

• CK-MB (CK-2) activity
 more specific than total CK
 BUT: less specific than troponin I (available in sk. Ms)

 appears in blood: within 4-6 hours of onset of attack
 peak:              12 - 24 hours
 returns to normal: within 2 - 3 days (no long stay in blood)

 Advantages: - useful for early diagnosis of MI
              - useful for diagnosis reinfarction

 Disadvantages: not used for delayed admission (more than 2 days)
                not 100% specific (elevated in damage)
• CK-MB mass
  - appears one hour earlier than CK-MB activity (more sensitive)

  - So, useful for diagnosis of early cases & reinfarction

  - BUT: not for diagnosis of delayed admission cases
        & less specific than troponin I

• Relative index = CK-MB mass / Total CK X 100
                   more than 5 % is indicative for MI
               Cardiac Proteins
• Myoglobin
 cytosolic protein

 - not specific for cardiac tissue (also in & renal tissue)

 - appears in blood EARLIER than other markers (within 1-4 hours)
   So, with high sensitivity

 - BUT: Returns to normal in 24 hours
       So, not for delayed admission cases (after one day of onset
                                            of attack)
•       Cardiac Troponins
    Protein complex located on the thin filament of striated muscles
    consists of 3 subunits: cTn T, cTnI & cTn C
                            with different structures & functions

    cTnI & cTnT are used are biomarkers for MI diagnosis

    Cardiac troponins (cTn) are different from skeletal muscle tropnins
    So, more specific for MI diagnosis


•       100 % cardiac specific
•       With greater sensitivity for diagnosing minor damage of MI
•       Appears in blood within 6 hours after onset of infarction
•       peak: around 24 hours
•       Disappears from blood after about one week (stays longer)
        So, useful for diagnosis of delayed admission cases
•       Prognostic marker (relation between level in blood & extent of cardiac
    Recommendations for use of biochemical
  markers for diagnosis of myocardial infarction
1- Recommended for all patients complaining of chest pain (with clinical examination & ECG)

2- Sample
    Type:   plasma
    Timing: i. on admission
            ii. serial ( at least every one hour in a period 6-9 hours)
            should be referenced to admission & onset of pain

3- Test should be with low turnaround time
           less than one hour (accepted)
           less than half an hour is preferred

4- Types of Markers used: two types
   early markers: as Myoglobin: appears in blood early (within less 4 fours)
                                  BUT not specific & not persists for long period (less than 2 days)

   definitive markers: Troponin:    appears in blood later than myoglobin (within 6 hours)
                                     BUT 100% specific, prognostic & stays longer (one week)

5- Troponin is currently the marker of choice
   should be available in all cardiac & emergency centers
   (if not, CK-MB mass is the second choice)

To top