Question

Reliable markers for Myocardial infarction except :

• A. Troponin I
• B. CKMB
• C. LDH
• D. ALT

Answer 1

Answer:

D. ALT

Biomarkers for Myocardial Infarction (MI)

• Cardiac Troponins (cTnI and cTnT): These are the gold standard for diagnosing MI. They are highly specific to cardiac tissue. They rise within 3-12 hours of symptom onset, peak at 24-48 hours, and remain elevated for 5-14 days.
• Creatine Kinase-MB (CK-MB): Historically a major marker, it rises within 3-12 hours, peaks at 24 hours, and returns to baseline within 48-72 hours. While useful for detecting re-infarction, it is less specific than troponins because it can be elevated in skeletal muscle injury.
• Myoglobin: This is an early marker, rising within 1-3 hours of injury and peaking at 4-12 hours. However, it lacks specificity for cardiac muscle, as it also rises with skeletal muscle damage and renal failure.
• Lactate Dehydrogenase (LDH): Historically used, LDH levels rise within 24-48 hours and peak at 3-6 days, staying elevated for up to 2 weeks. It is considered an outdated or non-reliable marker for acute MI diagnosis compared to modern troponin assays due to low specificity (found in RBCs, liver, and muscle).

Key Diagnostic Considerations:

1. Cardiac Specificity: Troponins are currently the preferred biomarkers because they detect even microscopic myocardial necrosis, which older markers often missed.
2. Sensitivity vs. Specificity: Modern high-sensitivity troponin assays (hs-cTn) have largely replaced earlier, less sensitive tests, allowing for much earlier diagnosis of MI.
3. Non-Reliable Markers: Parameters like Total CK (Creatine Kinase) or AST (Aspartate Aminotransferase) are no longer considered reliable indicators for MI diagnosis due to their broad distribution in various body tissues.