During myocardial ischaemia, the earliest ultrastructural change detectable within 15-30 minutes of onset is:
- A Mitochondrial swelling and clumping of nuclear chromatin ✓
- B Flocculent densities in mitochondria
- C Cell membrane rupture with nuclear pyknosis
- D Myelin figures and sarcolemmal disruption
Correct answer: A. Mitochondrial swelling and clumping of nuclear chromatin
Explanation
The earliest reversible ultrastructural changes in ischaemic myocardial cells (15-30 minutes) are mitochondrial swelling (due to loss of cristae structure from ATP depletion and ionic imbalance) and margination/clumping of nuclear chromatin. These changes reflect the cellular stress response before membrane integrity is lost. Flocculent densities in mitochondria represent amorphous calcium phosphate deposits and indicate irreversible injury (>30-40 minutes). Membrane rupture and myelin figures are also features of irreversible injury.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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