[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Heart](https://durgical.com/en/general-pathology/areas/heart/) › Toxic and radiation injury of the myocardium

# Toxic and radiation injury of the myocardium

- Lesion

Some cancer drugs, cocaine, high adrenaline, thyroid disease and chest radiation can damage the heart muscle directly.

Updated Nov 12, 2026

## Key points

- Anthracyclines: cumulative dose-dependent, often irreversible dilated cardiomyopathy; myocyte vacuolisation and loss of myofibrils.
- Trastuzumab (HER2 blockade): reduced contraction that usually recovers on stopping.
- Checkpoint inhibitors: rare but often fatal myocarditis, sometimes with myositis.
- Catecholamines and cocaine: contraction-band necrosis, coronary spasm, infarction, arrhythmia.
- Hyperthyroidism: high output, atrial fibrillation; hypothyroidism: flabby heart, pericardial effusion.
- Radiation: fibrosis of all layers years later, including coronary ostia and valves.

## What it is

The myocardium can be injured by toxins and hormones. Anthracyclines (doxorubicin) cause a dose-dependent dilated cardiomyopathy through oxidative and topoisomerase-related damage; trastuzumab causes a mostly reversible dysfunction; immune checkpoint inhibitors cause lymphocytic myocarditis. Catecholamines (pheochromocytoma, cocaine, intense stress, high-dose pressors) cause vasospasm, tachycardia and focal contraction-band necrosis. Thyroid disease changes the heart: hyperthyroidism causes tachycardia, atrial fibrillation and high-output failure; hypothyroidism causes low output and pericardial effusion. Chest radiation causes pericarditis, myocardial fibrosis, valve thickening and accelerated coronary disease.

## Structure

- Catecholamine injury: foci of hypercontracted myocytes with dense eosinophilic transverse bands and scattered inflammatory cells.
- Anthracycline injury: on electron microscopy, loss of myofibrils and vacuolisation from dilated sarcoplasmic reticulum.

## Toxic and endocrine injury to the myocardium

| Agent | Mechanism | Pathology | Clinical |
| --- | --- | --- | --- |
| Anthracyclines | Oxidative stress, topoisomerase II-β damage | Myocyte vacuolisation, myofibril loss, fibrosis | Dose-dependent dilated cardiomyopathy |
| Trastuzumab | Loss of HER2 survival signalling | Little structural damage | Mostly reversible dysfunction |
| Immune checkpoint inhibitors | T-cell attack on myocytes | Lymphocytic myocarditis | Arrhythmia, failure, high mortality |
| [Cocaine](https://durgical.com/en/conditions/cocaine-and-sympathomimetic-toxicity/) | Catecholamine excess, spasm, thrombosis | Contraction-band necrosis, infarcts | Chest pain, MI, arrhythmia |
| [Pheochromocytoma and stress](https://durgical.com/en/conditions/phaeochromocytoma/) | Catecholamine excess | Contraction-band necrosis, focal myocarditis | Arrhythmia, stress cardiomyopathy |
| [Hyperthyroidism](https://durgical.com/en/conditions/graves-disease/) | Increased metabolism and β-adrenergic sensitivity | Hypertrophy, little else | Tachycardia, AF, high-output failure |
| Chest radiation | Endothelial and fibroblast injury | Fibrosis of pericardium, myocardium, valves, coronary arteries | Constriction, restriction, early coronary disease |

## Clinical notes

- Patients receiving cardiotoxic cancer therapy are monitored with serial echocardiography (cardio-oncology).

## Memory aid

Red drug (doxorubicin) dilates, HER2 drugs stun and recover, adrenaline makes contraction bands, radiation scars every layer.

## Test yourself

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

## What determines anthracycline cardiotoxicity?

Mainly the cumulative dose; the resulting dilated cardiomyopathy is often irreversible.

## What is the typical lesion of catecholamine excess in the heart?

Focal contraction-band necrosis of myocytes.

## Which cardiac effect is classic for hypothyroidism?

Pericardial effusion with a flabby, low-output heart (also bradycardia).

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/toxic-and-radiation-injury-of-the-myocardium/)

[More Pathology questions →](https://durgical.com/en/practice/?f=pathology)

## Elsewhere in DurgiPedia

- [Cancer immunotherapy: checkpoint inhibitors, CAR-T and vaccines](https://durgical.com/en/immunology/cancer-immunotherapy-checkpoint-inhibitors-car-t-and-vaccines/)

## Connections

## Related 6

- [Injury by therapeutic drugs: the classic examples](https://durgical.com/en/general-pathology/injury-by-therapeutic-drugs-the-classic-examples/)
- [Ionizing radiation injury](https://durgical.com/en/general-pathology/ionizing-radiation-injury/)
- [Drugs of abuse: cocaine, opioids, amphetamines, cannabis](https://durgical.com/en/general-pathology/drugs-of-abuse-cocaine-opioids-amphetamines-cannabis/)
- [Dilated cardiomyopathy](https://durgical.com/en/general-pathology/dilated-cardiomyopathy/)
- [Myocarditis](https://durgical.com/en/general-pathology/myocarditis/)
- [Pericardial disease](https://durgical.com/en/general-pathology/pericardial-disease/)

## Related conditions 7

- [Cocaine and sympathomimetic toxicity](https://durgical.com/en/conditions/cocaine-and-sympathomimetic-toxicity/)
- [Phaeochromocytoma](https://durgical.com/en/conditions/phaeochromocytoma/)
- [Graves disease (hyperthyroidism)](https://durgical.com/en/conditions/graves-disease/)
- [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/)
- [Dilated cardiomyopathy](https://durgical.com/en/conditions/dilated-cardiomyopathy/)
- [Thyroid storm](https://durgical.com/en/conditions/thyroid-storm/)
- [Takotsubo (stress) cardiomyopathy](https://durgical.com/en/conditions/takotsubo-cardiomyopathy/)

[← 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: [Cardiomyopathy | Enlarged Heart | MedlinePlus](https://medlineplus.gov/cardiomyopathy.html) (MedlinePlus, US National Library of Medicine, 2025); [Dilated cardiomyopathy: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000168.htm) (MedlinePlus, US National Library of Medicine, 2025).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/general-pathology/toxic-and-radiation-injury-of-the-myocardium/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/toxic-and-radiation-injury-of-the-myocardium/