Serum Cardiac Marker

1. Indications
   1. Myocardial Infarction Evaluation
2. Protocol: Typical
   1. Troponin I every 4 to 6 hours for 3 samples
   2. Trend upward above discriminatory Troponin I values suggests acute Myocardial Infarction
3. Protocol: Troponin and CK-MB with 2 hour intervals
   1. Initial tests at presentation
      1. Troponin I or Ultrasensensitive Troponin T
      2. CK and CK-MB
   2. Tests at 2-4 hours after initial labs
      1. Troponin I
      2. CK and CK-MB
   3. Interpretation: Case in which acute Myocardial Infarction unlikely
      1. Initial Ultrasensitive Troponin T negative or
      2. Second Troponin I negative and CK-MB not increasing
   4. References
      1. Weingart in Majoewsky (2012) EM:RAP 12(4): 6-7
4. Protocol: Troponin and CK-MB every 8 hours for 3 samples (older protocol)
   1. Protocol
      1. Obtain Troponin at 0 hours, 8 hours and 16 hours
         1. Primary Cardiac Marker: Specific for cardiac event
         2. Not useful for monitoring event extension
            1. Levels stay elevated for 14 days
      2. Obtain CK-MB at 0 hours, 8 hours, and 16 hours
         1. Primary purpose: Follow cardiac event extension
         2. Decreases more rapidly than Troponin after event
   2. Test Sensitivity of combined protocol
      1. Test Sensitivity: >98% at 8 hours
      2. Test Specificity: 80 to 95% at 8 hours
   3. References
      1. Jernberg (2000) Am J Cardiol 86:1367-71
5. Labs: Troponin
   1. Rises: 3-6 hours
   2. Peaks: 20 hours
   3. Duration: 14 days
   4. Subunits
      1. Troponin T
      2. Troponin I
6. Labs: Creatine Phosphokinase (CPK)
   1. Rises: 4-6 hours
   2. Peaks: 12-24 hours
   3. Duration: 4-5 days
   4. Subunits (Fractionate to CK-MB only if CPK increased)
      1. CK-MB Fraction (duration for 2-3 days)
      2. CK-MB over 5% of total CPK suggests Myocardial Injury
7. Labs: Myoglobin
   1. Advantage: First Cardiac Marker to increase
   2. Disadvantage: Poor Specificity (only helps if negative)
   3. Rises: 1-2 hours
   4. Peaks: 4-6 hours
   5. Duration: 1-2 days
8. Labs: Glutamic oxaloacetic transaminase (AST, SGOT)
   1. Peaks: 24-36 hours
   2. Duration: 5 days
9. Labs: Lactic Dehydrogenase (LDH)
   1. Peaks: 24-48 hours
   2. Duration: 14 days
10. Labs: White Blood Cell Count
    1. Predicts adverse events in Unstable Angina
    2. Morbidity and mortality increase with increased WBCs
       1. WBC Count >10,000: High risk of adverse event
       2. WBC Count >15,000: Very high risk of adverse event
    3. References
       1. Cannon (2001) Am J Cardiol 87:636-9