General pathology · Hemodynamic disorders

The myocardial infarct over time: what the pathologist sees from hours to months !

Lesion

Dead heart muscle changes in a set order: hours of little change, days of neutrophils, a week of macrophages, and weeks to make a scar.

Updated 2026-11-01

What it is

After a coronary artery is blocked, the myocardium suffers irreversible injury within minutes of severe ischemia. The changes that follow happen in a fixed order, which lets the pathologist estimate the age of an infarct at autopsy: coagulative necrosis within hours, neutrophil infiltration at one to three days, macrophage clean-up in the first week, granulation tissue in the second, and a collagen scar over weeks to months. Each stage matches typical complications.

Step by step

A coronary artery is blocked; the myocardium switches to anaerobic metabolism and stops contracting within seconds.
After about twenty to forty minutes of severe ischemia, damage becomes irreversible in the subendocardium.
Necrosis spreads as a wave from subendocardium toward epicardium over the following hours.
Muscle enzymes and proteins leak into the blood: troponins rise.
Neutrophils arrive, then macrophages; the wall softens while dead tissue is removed.
Granulation tissue is replaced by collagen; the scar does not contract and may bulge.

Timeline of a myocardial infarct

Time	Gross appearance	Microscope (H&E)	Typical complication
First hours	No visible change	Wavy fibres at the edge; changes only by electron microscopy	Arrhythmias (sudden death)
Hours to one day	Dark mottling	Early coagulative necrosis: more eosinophilic cytoplasm, pyknotic nuclei, contraction bands at the edges	Arrhythmias, pump failure
One to three days	Mottled zone with a yellow-tan centre	Coagulative necrosis with loss of nuclei and striations; many neutrophils	Fibrinous pericarditis
Three to ten days	Soft yellow centre, hyperemic border	Dead fibres break down; macrophages engulf them; granulation tissue starts at the edge	Rupture of free wall, septum or papillary muscle
Two weeks to two months	Red-grey borders turning grey-white	Granulation tissue with new vessels and increasing collagen	Ventricular aneurysm, mural thrombus, Dressler syndrome
Over two months	Firm white scar	Dense collagen scar	Heart failure, aneurysm, arrhythmias

In the lab

Autopsy: triphenyltetrazolium chloride stains living myocardium red and leaves the infarcted zone pale, hours after the event.
Cardiac troponins rise in the first hours and stay high for more than a week.

Test yourself

Think of the answer, then tap the question to see it.

At what stage of an infarct is free-wall rupture most likely?

Roughly between day three and day ten, when macrophages remove dead tissue and there is not yet enough collagen.

Which inflammatory cell dominates one to three days after an infarct?

The neutrophil.

What is contraction-band necrosis?

Transverse eosinophilic bands from hypercontraction of myofibrils when calcium floods damaged cells, typical of reperfusion.

Which pericardial complication appears weeks after an infarct?

Dressler syndrome, a pericarditis of probable autoimmune origin.

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Heart attack: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2024); Heart Attack | Myocardial Infarction | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.