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# Restrictive cardiomyopathy and cardiac amyloidosis

- Lesion

In restrictive disease, a stiff heart cannot fill. Amyloid deposits are the commonest cause; scarring, granulomas and iron can do the same.

Updated Nov 12, 2026

## Key points

- Amyloid: Congo red-positive deposits with apple-green birefringence under polarised light, around myocytes and in vessels.
- Cardiac amyloid: thick ventricles with low-voltage ECG, diastolic failure, conduction disease.
- Transthyretin amyloid: wild-type (senile) in older men; mutant forms, such as V122I, common in people of African ancestry.
- AL amyloid: plasma-cell dyscrasias such as myeloma; worse prognosis.
- Sarcoidosis: non-caseating granulomas, heart block and ventricular arrhythmias.
- Endomyocardial fibrosis: fibrosis of the apices and inflow tracts in tropical regions; Löffler endomyocarditis with hypereosinophilia and mural thrombi.

## What it is

Restrictive cardiomyopathy is a primary decrease in ventricular compliance that impairs filling, while contraction is often near normal. The ventricles are normal in size or slightly enlarged and the atria are dilated. Causes include amyloidosis, sarcoidosis, radiation fibrosis, metastatic tumour, inborn storage diseases and iron overload, as well as endomyocardial diseases: endomyocardial fibrosis (tropical, children and young adults), Löffler endomyocarditis (eosinophilic) and endocardial fibroelastosis (infants). Cardiac amyloidosis is caused mainly by transthyretin (wild-type in older men, or mutant) or immunoglobulin light chains (AL).

## Structure

- Amyloid heart: firm, rubbery, waxy myocardium; small nodules in the atrial endocardium.
- Microscopy: pink acellular deposits surrounding myocytes and in intramural vessels; confirmed by Congo red and typing (mass spectrometry or immunohistochemistry).

## Causes of a stiff, restricted heart

| Cause | Pathology | Clue |
| --- | --- | --- |
| Amyloidosis (TTR or AL) | Extracellular amorphous pink deposits, Congo red positive | Low ECG voltage with thick walls; older men (TTR) |
| Hemochromatosis and iron overload | Iron in myocytes (Prussian blue) | Diabetes, liver disease, transfusions |
| [Sarcoidosis](https://durgical.com/en/conditions/sarcoidosis/) | Non-caseating granulomas, patchy scars | Heart block, ventricular arrhythmias |
| Radiation fibrosis | Interstitial fibrosis, also pericardium and valves | Chest irradiation years earlier |
| [Löffler endomyocarditis](https://durgical.com/en/conditions/hypereosinophilic-syndrome/) | Eosinophilic infiltrate, endocardial fibrosis, mural thrombus | Hypereosinophilia |
| Endomyocardial fibrosis and endocardial fibroelastosis | Dense fibrosis of the endocardium (apices, inflow) or fibroelastic endocardium in infants | Tropical children (EMF), infants (EFE) |

## Clinical notes

- Restrictive cardiomyopathy mimics constrictive pericarditis; the distinction matters because constriction can be treated surgically.

## Memory aid

Stiff heart, big atria: think amyloid first, then granulomas, iron, radiation and the eosinophils.

## Test yourself

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

## Which stain confirms cardiac amyloid, and what does it show?

Congo red, which shows apple-green birefringence under polarised light.

## Which type of amyloid causes most cardiac amyloidosis in older men?

Wild-type transthyretin (ATTR) amyloid.

## Which disease must be distinguished from restrictive cardiomyopathy because it can be treated surgically?

Constrictive pericarditis.

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## Connections

## Related 6

- [Special stains in diagnosis: Congo red, Prussian blue, PAS, Ziehl–Neelsen, Gram](https://durgical.com/en/general-pathology/special-stains-in-diagnosis-congo-red-prussian-blue-pas-ziehl-neelsen-gram/)
- [Cardiomyopathies: classification](https://durgical.com/en/general-pathology/cardiomyopathies-classification/)
- [Pericardial disease](https://durgical.com/en/general-pathology/pericardial-disease/)
- [Plasma cell disorders: MGUS to myeloma](https://durgical.com/en/general-pathology/plasma-cell-disorders-mgus-to-myeloma/)
- [Hemochromatosis: hepcidin, HFE and where iron settles](https://durgical.com/en/general-pathology/hemochromatosis-hepcidin-hfe-and-where-iron-settles/)
- [Sarcoidosis: the lung](https://durgical.com/en/general-pathology/sarcoidosis-the-lung/)

## Related conditions 5

- [Restrictive cardiomyopathy (amyloid, sarcoid, haemochromatosis)](https://durgical.com/en/conditions/restrictive-cardiomyopathy/)
- [Sarcoidosis](https://durgical.com/en/conditions/sarcoidosis/)
- [Hypereosinophilic syndrome](https://durgical.com/en/conditions/hypereosinophilic-syndrome/)
- [Constrictive pericarditis](https://durgical.com/en/conditions/constrictive-pericarditis/)
- [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: [Restrictive cardiomyopathy: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000189.htm) (MedlinePlus, US National Library of Medicine, 2025); [Amyloidosis: MedlinePlus](https://medlineplus.gov/amyloidosis.html) (MedlinePlus, US National Library of Medicine, 2025); [Transthyretin amyloidosis: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/transthyretin-amyloidosis/) (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/restrictive-cardiomyopathy-and-cardiac-amyloidosis/