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# Complications of myocardial infarction

- Lesion

After a heart attack, different problems strike at different times: rhythm problems first, wall rupture in the first week, aneurysm and failure later.

Updated Nov 12, 2026

## Key points

- Arrhythmias (ventricular fibrillation, heart block) are the main cause of early death, many before reaching hospital.
- Cardiogenic shock: when about 40 % or more of the left ventricle is infarcted.
- Rupture peaks between days 3 and 10, when macrophages have removed dead tissue and collagen is still weak.
- Posteromedial papillary muscle (single supply from the posterior descending artery) ruptures more often than the anterolateral.
- True ventricular aneurysm: late, a thin scar that bulges; rarely ruptures but causes thrombus, arrhythmia and failure.
- Right ventricular infarction (with inferior MI): hypotension with clear lungs and raised jugular pressure.

## What it is

The complications of myocardial infarction follow the healing timeline. In the first hours and days, arrhythmias and pump failure dominate. Between about the third and the tenth day the softened wall can rupture: the free wall (tamponade), the septum (acute VSD) or a papillary muscle (acute mitral regurgitation). Fibrinous pericarditis appears in transmural infarcts in the first days; autoimmune (Dressler) pericarditis weeks later. Mural thrombi, ventricular aneurysms and progressive heart failure come in the following weeks and months.

## Structure

- Rupture: a slit-like tear through soft necrotic myocardium with surrounding haemorrhage.
- Aneurysm: a thin, fibrous, bulging wall without muscle, often lined by laminated thrombus.
- Infarct expansion: early stretching and thinning of the infarcted segment, which favours aneurysm and thrombus.

## Complications of myocardial infarction on the healing timeline

| Complication | Usual timing | What happens |
| --- | --- | --- |
| [Arrhythmia](https://durgical.com/en/conditions/ventricular-tachycardia/) | First hours to days | Ventricular fibrillation, tachycardia, heart block; sudden death |
| [Cardiogenic shock](https://durgical.com/en/conditions/cardiogenic-shock/) | First days | Large infarct, low output |
| [Free-wall rupture](https://durgical.com/en/conditions/cardiac-tamponade/) | Days 3–10 | Hemopericardium and tamponade |
| [Papillary muscle rupture](https://durgical.com/en/conditions/mitral-regurgitation/) | Days 3–10 | Acute severe mitral regurgitation, pulmonary edema |
| [Septal rupture](https://durgical.com/en/conditions/mechanical-complications-of-myocardial-infarction/) | Days 3–10 | Acute VSD with left-to-right shunt |
| [Fibrinous pericarditis](https://durgical.com/en/conditions/acute-pericarditis/) | Days 1–3 | Friction rub over a transmural infarct |
| [Ventricular aneurysm and mural thrombus](https://durgical.com/en/conditions/mechanical-complications-of-myocardial-infarction/) | Weeks to months | Bulging scar, thromboembolism, arrhythmia, failure |
| [Dressler syndrome](https://durgical.com/en/conditions/acute-pericarditis/) | Weeks | Autoimmune pericarditis with fever and effusion |

## Clinical notes

- Sudden hypotension with a new murmur after an infarct suggests papillary muscle or septal rupture; sudden pulseless electrical activity suggests free-wall rupture with tamponade.

## Memory aid

Rhythm in the first hours, rupture in the soft week, aneurysm and Dressler after the month.

## Test yourself

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

## When is the risk of free-wall rupture highest after myocardial infarction, and why?

Around days 3 to 10, when macrophages have cleared the necrotic muscle but little collagen has been laid down.

## Why is the posteromedial papillary muscle more vulnerable?

It usually has a single blood supply (from the posterior descending artery), while the anterolateral one has a dual supply.

## What is Dressler syndrome?

A pericarditis appearing weeks after infarction or cardiac surgery, thought to be autoimmune, with fever and pericardial effusion.

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## Elsewhere in DurgiPedia

- [Cardiac tamponade: Beck triad and pulsus paradoxus](https://durgical.com/en/clinical-exam/cardiac-tamponade-beck-triad-and-pulsus-paradoxus/)

## Connections

## Related 5

- [The myocardial infarct over time: what the pathologist sees from hours to months](https://durgical.com/en/general-pathology/the-myocardial-infarct-over-time-what-the-pathologist-sees-from-hours-to-months/)
- [Myocardial infarction: pathogenesis](https://durgical.com/en/general-pathology/myocardial-infarction-pathogenesis/)
- [Systemic (arterial) thromboembolism](https://durgical.com/en/general-pathology/systemic-thromboembolism/)
- [Pericardial disease](https://durgical.com/en/general-pathology/pericardial-disease/)
- [Shock: types, stages and the organs it damages](https://durgical.com/en/general-pathology/shock-types-stages-and-the-organs-it-damages/)

## Related conditions 8

- [Mechanical complications of myocardial infarction](https://durgical.com/en/conditions/mechanical-complications-of-myocardial-infarction/)
- [Cardiogenic shock](https://durgical.com/en/conditions/cardiogenic-shock/)
- [Cardiac tamponade](https://durgical.com/en/conditions/cardiac-tamponade/)
- [Acute pericarditis](https://durgical.com/en/conditions/acute-pericarditis/)
- [Ventricular tachycardia](https://durgical.com/en/conditions/ventricular-tachycardia/)
- [Mitral regurgitation](https://durgical.com/en/conditions/mitral-regurgitation/)
- [Atrioventricular (heart) block](https://durgical.com/en/conditions/atrioventricular-block/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)

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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 | Myocardial Infarction | MedlinePlus](https://medlineplus.gov/heartattack.html) (MedlinePlus, US National Library of Medicine, 2025).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/complications-of-myocardial-infarction/