Endocardial fibroelastosis

What is endocardial fibroelastosis?¹

Endocardial fibroelastosis was first described by Weinberg and Himmelfarb in 1943 as a thick subendocardial layer of connective tissue and elastin, encapsulating the underlying myocardium of the left atrium and left ventricle.

The primary form, which is not associated with any significant structural anomaly of the heart, is rare, but endocardial fibroelastosis is still a major feature of several congenital heart diseases, most notably lesions with left heart obstructions including hypoplastic left heart syndrome.²

Pathogenesis

The disease can be primary or secondary, although some argue it is only ever secondary.³

The two forms of primary endocardial fibroelastosis (EFE) are dilated (most common), and contracted.⁴ It has been suggested that one form may progress to the other.

• Primary dilated EFE occurs when the heart is otherwise normal and there is no other cause of unexplained heart failure.

• Secondary dilated EFE is associated with aortic stenosis or atresia.

• Secondary contracted EFE is associated with hypoplastic left heart syndrome.

Endocardial fibroelastosis epidemiology⁴

• Primary endocardial fibroelastosis is rare - only 1-2% of all congenital heart diseases. The number of cases has fallen dramatically in recent years, possibly secondary to better antenatal scanning.

• It may be familial (10%) with a predominantly X-linked pattern.

• It affects both sexes equally, usually presenting during the first 3-6 months of life in 80% of cases.

• Typical age of diagnosis is 2-12 months. It rarely is reported in adolescents and adults.

• It is an important cause of non-immune hydrops fetalis.⁵

What causes endocardial fibroelastosis? (Aetiology)¹

The presence of endocardial fibroelastosis has been reported in several other cardiac diseases such as:

• Cardiomyopathies.

• Viral myocarditis.

• Lysosomal storage diseases.

• Congenital heart diseases such as aortic stenosis, coarctation of the aorta, or hypoplastic left heart syndrome.

The macroscopic and microscopic appearance led to the uniform diagnosis of endocardial fibroelastosis.

Endocardial fibroelastosis symptoms (presentation)

It typically presents with typical signs of congestive heart failure (CHF) in previously healthy children less than 6 months old.⁶

Symptoms

• Breathlessness.

• Cough.

• Wheezing.

• Feeding difficulty.

• Excessive sweating.

• Failure to thrive.

• Recurrent chest infections.

In children, severe abdominal pain may indicate coronary insufficiency.

Signs

Onset may be acute and result in cardiogenic shock or sudden death.⁷

• Respiratory distress during feeding - tachypnoea, grunting, subcostal or intercostal recession.

• Fever.

• Pallor (anaemia).

• Peripheral cyanosis.

• Cardiomegaly - normal or quiet first and second heart sounds, a gallop rhythm with an audible third heart sound.

• Apical pansystolic murmur.

• Hepatomegaly.

• Oedema.

• Rash.

• Leukocytosis.

There is also an increased risk of thromboembolic episodes.

It may present as part of Barth's syndrome, which comprises dilated cardiomyopathy ± endocardial fibroelastosis.⁸

Investigations

• Blood tests:
  

  • Blood urea and creatinine.

  • FBC.

  • Autoantibody profile (including anti-Ro and anti-La).⁹

  • Blood culture tests indicated for management of acute episodes.

• CXR:
  

  • Cardiothoracic (CT) ratio exceeds 0.65.

  • Left lower lobe atelectasis may be seen.

  • The cardiac silhouette is often globular.

  • Pulmonary venous congestion is common.

• ECG:
  

  • Tall R waves.

  • Deep Q waves.

  • T-wave inversion or flattening in the left precordial or inferior lead.

  • Findings depict left ventricular (LV) hypertrophy.

  • Right axis deviation and isolated right ventricular (RV) hypertrophy (more common in the first few weeks of life).

  • Left, right (or both) atrial enlargement.

  • Wolff-Parkinson-White syndrome, left bundle branch block, supraventricular and ventricular arrhythmias and varying degrees of atrioventricular block.

  • The early and terminal stages of heart failure show low-voltage tracings.

• Echocardiography:
  

  • Increase in left atrium and LV dimensions.

  • Reduced ejection fraction.

  • Abnormal mitral valve motion.

  • Dense echogenicity along the endocardium of the LV.

  • A varying degree of mitral regurgitation is common.

• Fetal echocardiography:
  

  • Valuable tool for early identification, particularly of the secondary type.

  • Doppler studies may be useful if the morphology is unclear.^{10 11}

• Although an echocardiogram is commonly performed, research has shown that cardiac magnetic resonance (CMR) might be more visual and accurate in evaluating morphological and functional cardiac changes.⁶

Endocardial fibroelastosis treatment and management

The management is as per the management of heart failure. In severe cases, surgical management with left ventricular decortication may be required.¹²

Cardiac transplantation may be recommended.

Prognosis

The prognosis for primary endocardial fibroelastosis is relatively poor:¹³

• The 4-year survival rate is 77%.

• It is worse in infants who present with acutely decompensated heart failure and they are less likely to survive unless they receive a transplant.

• Surviving patients often experience persistent symptoms.

• An ECG 'infarct' pattern in a child with endocardial fibroelastosis is usually associated with death and is a negative prognostic sign for survival.

The prognosis for secondary endocardial fibroelastosis is variable, depending on the underlying disease process and severity.