Endomyocardial fibrosis

Endomyocardial fibrosis (EMF) is an idiopathic disorder characterized by the development of restrictive cardiomyopathy.

Epidemiology

It usually occurs in tropical and subtropical regions of the world. There may be a greater predilection in children and adolescents. 

Pathology

The pathogenesis is poorly understood and is multifactorial with parasitic infestation, poverty, malnutrition, and genetic predisposition triggers inflammation and immunomodulation, inducing a profibrotic state that leads to fibrosis of the endomyocardium and development of ventricular apical obliteration ¹⁰.

It is characterized by focal or diffuse endocardial thickening within one or both ventricles secondary to diffuse fibrous tissue in the subendocardium ³. It typically involves the apices and then extends further basal typically including the posterior (inferior) wall in the left ventricle, can involve the papillary muscles and the chordae tendinae. It leads to a restriction of diastolic filling ^3,8, to thrombus formation, obliteration of the ventricular apices ⁵, calcifications which are typically subendocardial in nature and can lead to atrioventricular valve regurgitation ³.

Associations

It can occur as part of idiopathic hypereosinophilic syndrome ², resulting in so-called Loeffler endocarditis.

Clinical presentation

Acute phase: acute febrile illness, signs of myocarditis or thromboembolic events

Chronic phase: present with symptoms of restrictive heart failure, hepatosplenomegaly and disproportionate ascites. About third of patients develop atrial fibrillation ¹²

Radiographic features

Characteristic features are:

• ventricular apical obliteration by thrombus with or without calcifications
• secondary respective atrial enlargement
• atrioventricular valve regurgitation: tricuspid and mitral valve regurgitation secondary to fibrosis of the papillary muscles

Echocardiography

Widely available provides good morphologic and functional analysis and excellent in the evaluation of valvular disease.

Cardiac CT

CT allows good morphologic and functional analysis and differentiating thrombus from calcification.

Cardiac MRI

T1- and T2-weighted imaging: may differentiation of thrombi according to age.

Cine SSFP imaging:

• is the best for morphologic evaluation. The most distinctive feature is ventricular apical obliteration associated with enlargement of the respective atrium
• restrictive physiology with shrunken ventricles due to fibrosis ¹⁰:
  • mean indexed LV end-diastolic volume (LVEDV) reported
    to be 57 mL/m² ± 15
  • mean indexed RV end-diastolic volume (RVEDV) reported to be
    56 mL/m² ± 20
• LV or RV ejection fraction normal or mildly reduced
• can be used to assess the three-dimensional movement and morphology of the subvalvular apparatus

Early enhancement imaging: allow detection of ventricular thrombi

Delayed enhancement (DE) imaging: 

• subendocardial enhancement, not restricted to any coronary territory
• involving the ventricular apex and extending to the inflow tract sparing outflow tract orifices
• the typical pattern is the "double V" sign ¹¹, consists of a three-layered pattern of normal myocardium, thickened enhanced endomyocardium, and overlying thrombus at the ventricular apex with or without calcifications  
• provide prognostic information, with an increasing amount of apical fibrous tissue deposition indexed to BSA (>19 mL/m²) directly related to a worse prognosis

First-pass perfusion imaging: allow detection of apical thrombi.

Treatment and prognosis

The condition usually carries high morbidity and mortality with mean survival after diagnosis around two years. Death often results from chronic heart failure, arrhythmia and thromboembolism ³. Surgery may correct some structural and functional abnormalities but with uncertain, long-term outcomes.

Differential diagnosis

• apical hypertrophic cardiomyopathy (HCM)
  • asymmetric hypertrophy of apical segments
  • spade-shaped gradual obliteration of cardiac apex during systole
  • DE imaging shows patchy mid-wall enhancement, predominantly at the apex
• apical thrombus: usually associated with
  • wall thinning and motion abnormalities in myocardial infarction
  • apical aneurysm in non-ischemic cardiomyopathies
  • dilated cardiomyopathies in severe hypokinesia
• non-compaction of the left ventricle: the double-layered appearance of the myocardium with marked mid and apical trabeculae
• cardiac amyloidosis: diffuse ventricular hypertrophy, biatrial enlargement and interatrial septal thickening. It shows diffuse subendocardial or transmural enhancement
• apical neoplasm
• drug-induced restrictive cardiomyopathy
• post-radiation heart disease

History and etymology

It is thought to have been first described by W R Hardy and R E Anderson in 1968 ⁴.