A 55-year-old man presents 2 hours after the onset of acute chest pain. Troponin I is still within the reference range. Which serum marker would be expected to rise earliest at this stage?

• A Myoglobin ✓
• B CK-MB
• C LDH1
• D Aspartate aminotransferase

Explanation

Myoglobin, a small cytosolic protein abundant in cardiac and skeletal muscle, leaks rapidly through damaged membranes and becomes detectable in serum within 1 to 3 hours of infarction, making it the earliest rising marker. CK-MB appears around 4 to 6 hours, troponins around 3 to 4 hours, and AST and LDH rise later. Because myoglobin is also released from injured skeletal muscle, its specificity for myocardium is poor despite its early sensitivity.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.