Question

A histology slide of myocardium is taken from a patient who died 1-3 days after an acute myocardial infarction. Which of the following cellular changes is MOST characteristic of this time interval?

• A. Dense neutrophilic (polymorphonuclear) infiltration of necrotic myocardium
• B. Coagulative necrosis with wavy fibres and contraction bands only
• C. Macrophage infiltration with phagocytosis of dead myocytes
• D. Dense collagenous scar with few cells

Hint:

Acute inflammation dominates the first few days - think which white cell arrives first.

Answer 1

The Correct Option is A

The microscopic appearance of a myocardial infarct changes predictably with time, and the question asks for the 24-72 hour (1-3 day) picture.

Early on (first day, 4-24 h) the myocardium shows ongoing coagulative necrosis, wavy fibres at the margins, and contraction-band necrosis. By the second to third day, the dead muscle provokes a vigorous acute inflammatory reaction, so the slide is dominated by sheets of neutrophils infiltrating the necrotic zone. Their enzymes begin to break down the dead tissue.

After this, the inflammatory cast changes: macrophages move in around days 3-7 to phagocytose necrotic debris, granulation tissue with neovascularisation appears in the second week, and a firm collagenous scar is laid down over weeks 2-8. Therefore the macrophage, granulation, and scar options correspond to later intervals and are excluded.

Matching the 1-3 day window to its hallmark cell:
\[\boxed{\text{Neutrophilic (PMN) infiltration of necrotic myocardium}}\]