eMedicine Specialties > Cardiology > Myocardial Disease and Cardiomyopathies
Endomyocardial Fibrosis
Updated: Jan 17, 2006
Introduction
Background
Endomyocardial fibrosis (EMF) is an idiopathic disorder of the tropical and subtropical regions of the world that is characterized by the development of restrictive cardiomyopathy.
The nosology of EMF coincides with some related disorders. EMF is sometimes considered part of a spectrum of a single disease process that includes Löffler endocarditis (nontropical eosinophilic endomyocardial fibrosis or fibroplastic parietal endocarditis with eosinophilia).
Tropical EMF and Löffler endocarditis should be distinguished from endocardial fibroelastosis, which is characterized by cartilaginous thickening of the mural endocardium, chiefly of the left ventricle. This disease is most common in the first 2 years of life and, in some patients, appears to be an inherited disorder that is associated with congenital cardiac malformations.
Pathophysiology
In EMF, the underlying process produces patchy fibrosis of the endocardial surface of the heart, leading to reduced compliance and, ultimately, restrictive physiology as the endomyocardial surface becomes more generally involved. Endocardial fibrosis principally involves the inflow tracts of the right and left ventricles and may affect the atrioventricular valves, leading to tricuspid and mitral regurgitation.
The earliest changes of EMF are not well described because most patients do not present with symptoms until relatively late in the clinical course. Olsen described 3 phases of EMF. The first phase involves eosinophilic infiltration of the myocardium with necrosis of the subendocardium and a pathologic picture consistent with acute myocarditis. This is reportedly present in the first 5 weeks of the illness. The second stage, typically observed after 10 months, is associated with thrombus formation over the initial lesions, with a decrement in the amount of inflammatory activity present. Ultimately, after several years of disease activity, the fibrotic phase is reached, when the endocardium is replaced by collagenous fibrosis. Extensive calcification is rarely associated with fibrosis. This pathomorphologic schema is not observed uniformly and has not been consistently supported by other investigators.
The etiopathogenesis of EMF remains unclear. Hypotheses include infectious, inflammatory, and nutritional processes. EMF is frequently associated with concomitant parasitic infections (eg, helminths) and their attendant eosinophilia, although the role of parasitic infections and/or the eosinophil remains speculative. The development of EMF as a sequela to toxoplasma-related myocarditis has also been described, as has a relationship of malarial infection to development of EMF. However, no specific organism has been consistently associated with EMF.
The role of the eosinophil in the pathogenesis of EMF is controversial. Whether the eosinophil actually induces myocardial necrosis and subsequent fibrosis or is attracted to the endocardial surface as a result of the initial insult is unknown. The eosinophil is not present as frequently in cases of tropical EMF as in Löffler endocarditis; thus, the role of the eosinophil in the tropical disease is likely less significant.
EMF is most frequently observed in the socially disadvantaged and in children and young women. These groups frequently have malnutrition, and in regions of sub-Saharan Africa where the disease is most prevalent, the typical diet is high in a tuber called cassava, which contains relatively high concentrations of the rare earth element cerium (Ce). The combination of high Ce levels and hypomagnesemia has been shown to produce EMF-like lesions in laboratory animals.
A familial tendency has rarely been noted in Uganda and Zambia.
Frequency
United States
EMF is rarely encountered in patients who have not traveled from the subtropical regions of Africa and tropical and subtropical regions elsewhere in the world, including areas in India and South America that are within 15° of the equator. Löffler endocarditis (also called nontropical eosinophilic endocarditis) is a related condition that is observed in the United States and is considered by some authors to be a different stage of a similar process related to eosinophilia.
International
EMF occurs primarily in the subtropical regions of Africa but is also encountered in tropical and subtropical regions elsewhere in the world, including areas in India and South America that are within 15° of the equator.
More than 90% of reported cases of EMF have occurred in geographic locations that are within 15° of the equator. In equatorial African nations, such as Nigeria, EMF is the fourth most common cause of cardiac disease in adults, and EMF accounts for 22% of cases of heart failure in Nigerian children. EMF is the most common type of restrictive cardiomyopathy in tropical countries.
Mortality/Morbidity
- The overall prognosis of patients with EMF is poor and depends on the extent and distribution of disease within the various chambers and valves of the heart.
- Most patients have extensive disease at the time of presentation; therefore, survival after diagnosis is relatively brief. In one study, 95% of a group of patients had died at 2 years. In a second study, 44% of patients died within 1 year after the onset of symptoms, and another 40% of patients died 1-3 years after onset.
Race
EMF is most commonly reported in individuals living in Nigeria and Uganda.
Sex
Women of reproductive age and children are more commonly affected than men.
Age
- EMF is not generally observed in children younger than 4 years, although the typical pathology for EMF has recently been described in a 4-month-old infant with left ventricular inflow tract obstruction.
- The people most commonly affected are older children (aged 5-15 y) and young adults, but cases have been reported in individuals aged 70 years.
Clinical
History
Typically, endomyocardial fibrosis (EMF) has an insidious onset, and symptoms relate to the specific chambers and valves where the disease is most extensive.
- When right ventricular involvement or tricuspid regurgitation predominates, lower extremity swelling, increasing abdominal girth, and nausea may be expected.
- With left ventricular involvement, dyspnea is the predominant symptom, especially exertional dyspnea. Additionally, fatigue, paroxysmal nocturnal dyspnea, and orthopnea may be present.
- Thromboembolic complications may occur in EMF.
- Rarely, patients may present early in the course of the disease with an acute febrile illness with symptoms of cardiac insufficiency mimicking myocarditis.
- Recently, anginalike chest pain and syncope were reported in a patient with EMF involving the left ventricle.
Physical
Physical findings are also dependent on the extent and distribution of disease.
- In those with right ventricular involvement, jugular venous pressure elevation, ascites, and edema may be present.
- The presence of ascites may appear out of proportion to the amount of peripheral edema. This may occur because of the concomitant presence of a protein-losing enteropathy and subsequent hypoalbuminemia.
- Patients with tricuspid regurgitation may have giant V waves observed in the jugular venous pulsations.
- A third or fourth heart sound and tachycardia may be present.
- Signs of pulmonary congestion are present in patients with left-sided disease.
Causes
A specific single etiology of EMF has not been established. Suggested potential causes include the following:
- Infectious causes
- Parasites (eg, helminths)
- Protozoans (eg, toxoplasmosis, malaria)
- Inflammatory causes - Eosinophilia
- Nutritional causes
- General malnutrition
- High-tuber diet
- Ce toxicity
- Hypomagnesemia
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| Follow-up: Endomyocardial Fibrosis |
| References |
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Further Reading
Keywords
endomyocardial fibrosis, EMF, endomyocardial disease, hypereosinophilic syndrome, obliterative myocardial disease, tropical eosinophilic endomyocardial fibrosis, Davies disease, endocardial fibroelastosis, endomyocardial fibroelastosis, Löffler endocarditis, Loeffler endocarditis, restrictive cardiomyopathy, fibrosis of the endocardial surface of the heart, acute myocarditis, parasites, helminths, protozoans, toxoplasmosis, malaria, eosinophilia, malnutrition, high-tuber diet, cerium toxicity, Ce toxicity, hypomagnesemia, constrictive pericarditis
