Question

Name the enzyme which is the oldest known marker used for myocardial infarction

• A. Lactate dehydrogenase
• B. Creatine kinase
• C. Alanine aminotransferase
• D. Alkaline phosphatase

Hint:

Although modern medicine relies on highly specific Cardiac Troponins (I and T) as primary diagnostics, historically, the combination of AST, LDH, and CK was used to confirm myocardial infarction.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Myocardial infarction (heart attack) causes necrosis of cardiac muscle cells.
This injury ruptures membranes and releases intracellular enzymes and proteins into the bloodstream.
These released substances serve as diagnostic biomarkers to confirm cardiac tissue damage.

Step 2: Detailed Explanation:
Historically, clinical chemistry identified serum enzymes to diagnose myocardial infarction starting in the mid-20th century.
The timeline of enzyme biomarker adoption includes:
Aspartate Aminotransferase (AST/SGOT): Discovered as the first cardiac biomarker in 1954 by Ladue et al., though it is not listed among the options.
Lactate Dehydrogenase (LDH): Introduced in 195 It is the oldest marker among the options provided. LDH levels begin to rise 12 to 24 hours after an infarction, peak within 48 to 72 hours, and can remain elevated for up to 10 to 14 days.
Creatine Kinase (CK): Specifically the CK-MB isoenzyme, introduced in the late 1960s as a more specific option.
Among the available choices, Lactate Dehydrogenase represents the oldest historical enzyme biomarker for diagnosing myocardial injury.

Step 3: Final Answer:
Lactate dehydrogenase is the oldest known marker among the choices used for myocardial infarction.