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# 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

## Key points

- First hours: almost nothing visible by light microscopy; perhaps wavy fibres.
- One to three days: established coagulative necrosis with neutrophils; risk of fibrinous pericarditis.
- Three to ten days: macrophages; the wall is at its softest and ruptures most often (free wall, septum, papillary muscle).
- Two weeks onward: granulation tissue then scar; ventricular aneurysm and mural thrombus.
- Weeks later: autoimmune pericarditis (Dressler syndrome).
- Reperfusion: hemorrhage within the infarct and contraction-band necrosis.

## 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.

## Memory aid

Neutrophils by day three, macrophages by the week, granulation by the fortnight, scar by two months; and rupture when the wall is softest.

## 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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## Related

- [Infarction: red vs white, and what decides the damage](https://durgical.com/en/general-pathology/infarction-red-vs-white-and-what-decides-the-damage/)
- [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/)
- [Hypoxia, ischemia and reperfusion injury](https://durgical.com/en/general-pathology/hypoxia-ischemia-and-reperfusion-injury/)
- [Granulation tissue and scar formation](https://durgical.com/en/general-pathology/granulation-tissue-and-scar-formation/)

## Related conditions

- [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/)
- [Mechanical complications of myocardial infarction](https://durgical.com/en/conditions/mechanical-complications-of-myocardial-infarction/)
- [Acute pericarditis](https://durgical.com/en/conditions/acute-pericarditis/)
- [Cardiac tamponade](https://durgical.com/en/conditions/cardiac-tamponade/)
- [Mitral regurgitation](https://durgical.com/en/conditions/mitral-regurgitation/)
- [Cardiogenic shock](https://durgical.com/en/conditions/cardiogenic-shock/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)

## Elsewhere in DurgiPedia

- [The ECG in ischemia and infarction](https://durgical.com/en/physiology/the-ecg-in-ischemia-and-infarction/)
- [Coronary circulation and myocardial ischemia](https://durgical.com/en/physiology/coronary-circulation-and-myocardial-ischemia/)
- [Cardiac muscle: intercalated discs](https://durgical.com/en/histology/cardiac-muscle-intercalated-discs/)
- [Neutrophil](https://durgical.com/en/immunology/neutrophil/)
- [Monocyte and macrophage](https://durgical.com/en/immunology/monocyte-and-macrophage/)
- [Wound healing: phases and scar](https://durgical.com/en/histology/wound-healing-phases-and-scar/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

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](https://medlineplus.gov/ency/article/000195.htm) (MedlinePlus, US National Library of Medicine, 2024); [Heart Attack | Myocardial Infarction | MedlinePlus](https://medlineplus.gov/heartattack.html) (MedlinePlus, US National Library of Medicine, 2026).

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