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Restrictive Cardiomyopathy & Amyloid Heart

TL;DR

For Cardio: Restrictive Cardiomyopathy & Amyloid Heart, MRCP Part 1 tests your ability to recognise diastolic dysfunction with preserved systolic function, especially the hallmark ECG–echo mismatch seen in cardiac amyloidosis. Think “stiff ventricles, normal size, enlarged atria,” alongside systemic features like neuropathy or macroglossia. Differentiating restrictive cardiomyopathy from constrictive pericarditis is a recurring exam theme.


Why this matters

Restrictive cardiomyopathy (RCM) is a classic MRCP Part 1 topic because it blends physiology, imaging, and systemic disease recognition. It is often tested through pattern recognition, especially distinguishing it from constrictive pericarditis and hypertrophic cardiomyopathy.

Use this alongside the MRCP Part 1 overview and reinforce with Free MRCP MCQs or a Start a mock test.


Core concepts you must know

1) Definition and Pathophysiology

Restrictive cardiomyopathy is defined by:

  • Impaired ventricular filling (diastolic dysfunction)

  • Normal or near-normal systolic function (early stages)

  • Non-dilated ventricles with increased stiffness

The key issue is reduced compliance, leading to elevated filling pressures and atrial enlargement.

2) Causes of Restrictive Cardiomyopathy (High-Yield List)

Infiltrative (most tested):

  • Amyloidosis (AL, ATTR)

  • Sarcoidosis

Storage disorders:

  • Haemochromatosis

  • Fabry disease

Endomyocardial:

  • Endomyocardial fibrosis

  • Loeffler’s syndrome (eosinophilic)

Others:

  • Radiation-induced heart disease

👉 Exam tip: Amyloidosis is by far the most commonly tested cause.

3) Cardiac Amyloidosis (Exam Favourite)

Amyloid deposition within the myocardium leads to stiff ventricles and restrictive physiology.

Types relevant for MRCP:

  • AL (light-chain): Associated with multiple myeloma or plasma cell dyscrasia

  • ATTR: Transthyretin-related (hereditary or wild-type in elderly)

4) ECG–Echo Discordance (Must-Know Pattern)

Feature

Finding in Cardiac Amyloidosis

ECG

Low voltage QRS complexes

Echo

Increased ventricular wall thickness

Atria

Enlarged

Filling pattern

Restrictive

👉 Key concept: Thick myocardium on echo + low voltage ECG = amyloidosis until proven otherwise.

5) Clinical Features

Patients typically present with:

  • Progressive dyspnoea

  • Peripheral oedema

  • Ascites

  • Fatigue

Red-flag systemic clues (very high yield):

  • Macroglossia

  • Periorbital purpura

  • Nephrotic syndrome

  • Peripheral neuropathy

6) Investigations (Structured Approach)

Echocardiography:

  • Normal LV size

  • Thickened walls

  • Biatrial enlargement

  • Restrictive filling pattern

ECG:

  • Low voltage

  • Pseudo-infarction Q waves

Cardiac MRI:

  • Diffuse late gadolinium enhancement

Definitive diagnosis:

  • Tissue biopsy with Congo red staining → apple-green birefringence

7) RCM vs Constrictive Pericarditis (Classic MRCP Comparison)

Feature

Restrictive Cardiomyopathy

Constrictive Pericarditis

Pathology

Myocardium

Pericardium

Pericardium

Normal

Thickened/calcified

BNP

Elevated

Normal/mild

Treatment

Medical

Surgical (pericardiectomy)

👉 Exam trap: Both have diastolic dysfunction—look for pericardial thickening and respiratory variation in constrictive pericarditis.

8) Management Principles

General:

  • Diuretics (use cautiously)

  • Treat underlying cause

Amyloidosis-specific:

  • AL → chemotherapy (e.g. bortezomib-based regimens)

  • ATTR → tafamidis

Advanced disease:

  • Consider heart transplantation

9) High-Yield Summary (Quick Revision)

  1. RCM = diastolic dysfunction with preserved EF

  2. Ventricles normal size, atria enlarged

  3. Amyloidosis = most tested cause

  4. ECG low voltage despite thick myocardium

  5. Systemic signs are key clues

  6. Differentiate from constrictive pericarditis

  7. Echo + MRI are essential investigations

  8. Congo red staining confirms diagnosis

  9. Diuretics must be used carefully

  10. Always consider systemic disease

Medical student revising cardiology topics for MRCP Part 1 including restrictive cardiomyopathy and amyloid heart

Practical examples / mini-case

MCQ

A 70-year-old man presents with fatigue and ankle swelling. ECG shows low voltage complexes. Echocardiography reveals increased ventricular wall thickness with normal cavity size and biatrial enlargement.

What is the most likely diagnosis?

A) Hypertrophic cardiomyopathyB) Dilated cardiomyopathyC) Cardiac amyloidosisD) Constrictive pericarditisE) Aortic stenosis

Answer: C) Cardiac amyloidosis

Explanation: The key feature is ECG–echo discordance—low voltage on ECG despite increased wall thickness. This is highly suggestive of cardiac amyloidosis.


Common pitfalls

  • Confusing RCM with constrictive pericarditis

  • Assuming thick myocardium always means hypertrophy

  • Missing low-voltage ECG clue

  • Ignoring extracardiac signs (e.g. neuropathy)

  • Over-diuresis worsening symptoms


FAQs

1) How is restrictive cardiomyopathy different from hypertrophic cardiomyopathy?

RCM has normal ventricular size with impaired filling, whereas HCM shows asymmetric hypertrophy and dynamic outflow obstruction.

2) Why does amyloidosis cause low voltage ECG?

Amyloid deposits disrupt electrical conduction, reducing signal amplitude despite increased wall thickness.

3) What is the gold standard for diagnosis?

Biopsy with Congo red staining demonstrating apple-green birefringence.

4) What is the key MRCP exam clue?

Low voltage ECG with thickened myocardium on echocardiography.

5) Is restrictive cardiomyopathy reversible?

Depends on cause—some forms (e.g. amyloidosis) may improve with disease-specific treatment, but many are progressive.


Ready to start?

Consolidate your understanding with Free MRCP MCQs and test your exam readiness using a Start a mock test. For structured preparation, revisit the MRCP Part 1 overview and integrate this topic with heart failure and pericardial disease.


Sources

 
 
 

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